As filed with the United States Securities and Exchange Commission on December 9, 2020

6,500,000 Ordinary Shares

(Including Ordinary Shares In the Form of American Depositary Shares)

 

€    per Ordinary Share

$    per American Depositary Share

Nanobiotix S.A. is offering 6,500,000 ordinary shares in a global offering consisting of (i) a public offering in the United States of     ordinary shares in the form of American Depositary Shares (“ADSs”), each representing one ordinary share (the “U.S. offering”) and (ii) an offering of     ordinary shares outside of the United States exclusively addressed to “qualified investors,” as such term is defined in article 2(e) of the Regulation (EU) No. 2017/1129 of the European Parliament and Council of June 14, 2017, through certain of the underwriters named in this prospectus (the “European offering”). Our ordinary shares are listed on the regulated market of Euronext in Paris (“Euronext Paris”) under the symbol “NANO.” This is our initial public offering in the United States. Our ADSs have been approved for listing on the Nasdaq Global Select Market under the symbol “NBTX.” On December 9, 2020, the last reported sale price of our ordinary shares on Euronext Paris was €12.60 per ordinary share, equivalent to a price of $15.26 per ADS, based on an exchange rate of €1.00 = $1.2109 on December 9, 2020.

The U.S. offering and the European offering are collectively referred to in this prospectus as the offering. The total number of ordinary shares (including those in the form of ADSs) in the U.S. offering and the European offering is subject to reallocation between them. We expect the offering price per ADS in U.S. dollars and the corresponding offering price per ordinary share in euros will be between €11.15 and €11.97 per ordinary share and between $13.50 and $14.50 per ADS, respectively, and in any event will not be lower than 10% below the volume-weighted average price of our ordinary shares on the regulated market of Euronext in Paris for the three trading days preceding the appropriate reference date.

We are an “emerging growth company” as that term is used in the Jumpstart Our Business Startups (JOBS) Act of 2012 and, as such, have elected to comply with certain reduced public company reporting requirements.

Investing in the ordinary shares (including those in the form of ADSs) involves risks that are described in the “Risk Factors” section beginning on page 15 of this prospectus.

We have agreed to issue, at the option of the underwriters, within 30 days from the date of this prospectus, up to an aggregate of 975,000 additional ordinary shares (including in the form of ADSs) to be sold to the several underwriters at the applicable offering price. If the underwriters exercise this option in full, the total underwriting commissions payable by us will be €    ($    ) and the total proceeds to us, before expenses, will be €    ($    ).

Neither the Securities and Exchange Commission nor any U.S. state or other securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

For the U.S. offering, the ADSs will be ready for delivery on or about    , 2020, through the book-entry facilities of The Depository Trust Company. For the European offering, the ordinary shares will be ready for delivery on or about    , 2020 through the book-entry facilities of Euroclear France.

The date of this prospectus is    , 2020.

We are responsible for the information contained in this prospectus and any free-writing prospectus we prepare or authorize. We and the underwriters have not authorized anyone to provide you with different information, and we and the underwriters take no responsibility for any other information others may give you. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should not assume that the information contained in this prospectus is accurate as of any date other than its date.

For investors outside the United States: Neither we nor any of the underwriters have done anything that would permit the offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the ADSs and ordinary shares and the distribution of this prospectus outside the United States.

We are incorporated in France, and a majority of our outstanding securities are owned by non-U.S. residents. Under the rules of the U.S. Securities and Exchange Commission (the “SEC”), we are currently eligible for treatment as a “foreign private issuer.” As a foreign private issuer, we will not be required to file periodic reports and financial statements with the SEC as frequently or as promptly as domestic registrants whose securities are registered under the Securities Exchange Act of 1934, as amended.

Our financial statements are presented in euros and, unless otherwise specified, all monetary amounts presented in this prospectus are in euros. All references in this prospectus to “$,” “dollars” and “USD” mean U.S. dollars and all references to

“€” mean euros. In various places throughout this prospectus, we show financial amounts in both U.S. dollars and euros. Unless otherwise noted, these translations, which are provided solely for convenience, are made at the exchange rate of €1.00 = $1.1237, the noon buying rate of the Federal Reserve Bank of New York on June 30, 2020. Throughout this prospectus, references to ADSs mean ADSs or ordinary shares represented by such ADSs, as the case may be.

Unless otherwise indicated, information contained in this prospectus concerning our industry and the markets in which we operate, including our general expectations and market position, market opportunity and market size estimates, is based on information from independent industry analysts, third-party sources and management estimates. Management estimates are derived from publicly available information released by independent industry analysts and third-party sources, as well as data from our internal research, and are based on assumptions made by us based on such data and our knowledge of such industry and market, which we believe to be reasonable. In addition, while we believe the market opportunity information included in this prospectus is generally reliable and is based on reasonable assumptions, such data involves risks and uncertainties and are subject to change based on various factors, including those discussed under the heading “Risk Factors.”

We own various trademark registrations and applications, and unregistered trademarks and service marks. “Nanobiotix,” “NBTX” (including, among others, referring to NBTXR3), the Nanobiotix logo and other trademarks or service marks of Nanobiotix S.A. appearing in this prospectus are the property of Nanobiotix S.A. or its subsidiaries. Solely for convenience, the trademarks, service marks and trade names referred to in this prospectus are listed without the ® and ™ symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto. All other trademarks, trade names and service marks appearing in this prospectus are the property of their respective owners. We do not intend to use or display other companies’ trademarks and trade names to imply any relationship with, or endorsement or sponsorship of us by, any other companies.

Investing in our ordinary shares (including ordinary shares in the form of ADSs) involves a high degree of risk. You should carefully consider the risks and uncertainties described below, together with all of the other information in this prospectus, including our consolidated financial statements and related notes, before deciding whether to purchase our securities. If any of the following risks are realized, our business, financial condition, operating results and prospects could be materially and adversely affected. In that event, the market price of our securities could decline, and you could lose part or all of your investment.

Our operating history has been focused primarily on research and development and the advancement of the clinical trial program for our lead product candidate, NBTXR3. A key element of our strategy is to use and expand our proprietary technology to continue to develop our innovative product candidates designed to enhance the efficacy of radiotherapy and to progress these candidates through clinical development for the treatment of a wide variety of cancers, including STS, head and neck cancers, liver cancers, prostate cancer and rectal cancer. The nanotechnology underlying our product candidates, specifically the use of nanosized radiation enhancers as a cancer treatment method, is novel. Although in April 2019, we successfully completed the applicable conformity assessment procedure for affixing the CE marking to our NBTXR3 device for the treatment of locally advanced STS, enabling commercialization of the product in the European Union for such indication, we have not yet commercialized the product nor generated any revenues from the sale of any approved products and we may ultimately not be able to generate substantial revenue from the commercialization of approved products.

We have encountered, and will continue to encounter, risks and difficulties frequently encountered by growing companies in new and rapidly evolving fields, particularly as we seek to utilize nanotechnology to provide solutions to unmet therapeutic needs in oncology. Consequently, the ability to predict our future operating results or business prospects is more limited than if we had a portfolio of approved products on the market.

We may not be able to fully implement or execute on our commercial strategy or realize, in whole or in part or within our expected time frames, the anticipated benefits of our growth strategies. You should consider our business and prospects in light of the risks and difficulties we face as a growing company focused primarily on the development and advancement of clinical trials.

We have not generated significant revenues and have incurred significant operating losses since our inception. To date, our limited revenues and other income have been derived primarily from payments under our exclusive license and collaboration agreement with PharmaEngine and research tax credits. We have not generated revenues to date from product sales or royalties, and we do not expect to generate significant revenues from product sales or royalties unless and until our product candidates are successfully commercialized following regulatory approval. We incurred net losses of €20.6 million for the six months ended June 30, 2020 and €50.9 million for the year ended December 31, 2019. The amount of our future net losses will depend, in part, on the amount of our future operating expenses and the pace at which they are incurred and our ability to obtain funding through our commercialization activities, through equity or debt financings or through research grants or collaborative partnerships. As of the date of this prospectus, our losses are primarily attributable to expenditures committed to developing our nanotechnology and our clinical and preclinical programs. We expect to continue to incur significant expenses and losses for the foreseeable future. We anticipate that such expenses and capital requirements will increase substantially as we:

The net losses we incur may fluctuate significantly from year-to-year such that a period-to-period comparison of our results of operations may not be a good indication of our future performance. In any particular period or periods, our operating results could be below the expectations of securities analysts or investors, which could cause the price of our ordinary shares and ADSs to decline.

Our business and future success depends heavily on our ability to develop and commercialize our lead product candidate, NBTXR3, for indications for which there is an attractive market opportunity, and to satisfy the necessary regulatory requirements for its marketing and sale. Our development programs of NBTXR3 for the treatment of different cancer indications are at varying stages. Because each of our ongoing and contemplated trials involves NBTXR3, if one of these preclinical or clinical trials reveals safety and/or therapeutic efficacy issues, the validity of our nanotechnology platform itself could be questioned, which could potentially require additional time and investment in research and development to attempt to remedy the issues identified. The development of each application of NBTXR3 could subsequently be impacted, potentially having a significant negative impact on our business prospects, financial situation and anticipated growth.

Although we successfully completed the applicable conformity assessment procedure for affixing the CE marking to our NBTXR3 device for the treatment of locally advanced STS, enabling the commercialization of the product in the European Union for such indication, NBTXR3 remains in clinical development for other indications, and we cannot be certain that NBTXR3 will receive regulatory approval or successfully complete the necessary conformity assessment procedures, as applicable, or be successfully commercialized, for any additional cancer indications, even if we successfully complete applicable pre-marketing regulatory requirements. Any failure or delay in the development or commercialization of NBTXR3 could have a material adverse effect on our business, financial condition and prospects.

The development of treatments for cancer is subject to rapid technological change. Many companies, academic research institutions, governmental agencies and public and private research institutions are pursuing the development of medicinal products, devices and other therapies that target the same conditions that we are targeting. Certain companies are developing treatments to increase sensitivities of tumors to radiation and other sources of energy. Like us, these companies are pursuing various technologies that involve substances that work to destroy tumor cells from the inside without causing additional damage to surrounding healthy tissues. Any product candidates that we develop and commercialize may compete with existing therapies, as well as new therapies that may become available in the future, including therapies with a mode of action similar to that of NBTXR3.

Many of our competitors, either alone or with their collaboration partners, may have significantly greater financial resources and expertise in research and development, preclinical testing, clinical trials, manufacturing, and marketing than we do. Future collaborations and mergers and acquisitions may result in further resource concentration among a smaller number of competitors. These competitors also compete with us in recruiting and retaining qualified research and development and management personnel and establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs. Smaller or early stage companies may also prove to be significant competitors, particularly through collaborative arrangements with more established companies.

The key competitive factors affecting the success of NBTXR3 and any other product candidates that we develop, if approved, are likely to be their efficacy, safety, convenience, price and the availability of reimbursement from government and other third-party payors. We must also protect our proprietary technology used in the development of our product candidates. Our commercial opportunity could be reduced if our competitors develop and commercialize products that are more effective or demonstrate a more favorable safety profile than any products that we may develop. Similarly, our commercial opportunity could be reduced if we fail to protect or to enforce our intellectual property rights successfully against third parties who infringe our patents or our licensors’ patents, or if competitors design around our patent claims or our licensors’ patent claims to produce competitive products, product candidates, processes and technologies that fall outside of the scope of our or our licensors’ patents. Our competitors may also successfully complete applicable pre-marketing regulatory requirements for their products more rapidly than us.

In December 2019, a new strain of coronavirus, SARS-CoV-2, identified as the cause of coronavirus disease 2019 (COVID-19), emerged. Since then, SARS-CoV-2 and the resulting disease COVID-19 has spread to many countries, including each of the countries in which our clinical trials are planned or ongoing.

As a result of the COVID-19 pandemic, governmental authorities have implemented and are continuing to implement numerous and rapidly evolving measures to try to contain the virus, such as travel bans and restrictions, limits on gatherings, quarantines, shelter-in-place orders, and business shutdowns. In response to the COVID-19 pandemic and in accordance with governmental orders, we have also modified our business practices and implemented proactive measures to protect the health and safety of employees, including restricting employee travel, requiring remote work arrangements for non-laboratory employees, implementing social distancing and enhanced sanitary measures in our facilities, and cancelling attendance at in-person events and conferences. Many of the suppliers and service providers on whom we rely have made similar modifications. There is no certainty that such measures will be sufficient to mitigate the risks posed by, or the impacts and disruptions of, the COVID-19 pandemic.

As a result of the COVID-19 pandemic, we have experienced, and expect to continue to experience, disruptions and adverse impacts to our business, including delays in certain clinical trial activities. Although the ultimate impact of the COVID-19 pandemic on our business is not determinable at this stage, the operational and functional impacts of the COVID-19 pandemic could be material, including:

While recruitment and monitoring in our clinical trials have slowed due to the pandemic and based on current circumstances, we expect that the receipt and reporting of data in head and neck cancer and immuno-oncology (“I-O”) clinical trials that were underway prior to the pandemic will generally proceed as planned based on the number of patients that had already been recruited. We anticipate that, as a result of the disruptions of the COVID-19 pandemic, protocol development and review processes and enrollment are likely to be delayed or to progress more slowly than originally anticipated. Moreover, given recruitment barriers, we expect delays in launching these trials even after regulatory clearance to proceed is obtained.

The degree to which COVID-19 ultimately impacts our business will depend on future developments, which are highly uncertain and cannot be predicted, including, but not limited to, the severity, duration and geographic spread of the outbreak, and the global, national and regional actions to contain the virus and address its impact. The resumption of normal business operations after interruptions caused by COVID-19 may be delayed or constrained by lingering effects of COVID-19 on us or our suppliers and third-party service providers, respectively. Even after the COVID-19 outbreak has subsided, we may experience material and adverse impacts as a result of the global economic impact of the COVID-19 outbreak.

The impact of COVID-19 may also exacerbate other risks discussed in this prospectus, any of which could have a material effect on us. This situation is changing rapidly and additional impacts may arise that we are not aware of currently.

Because we have limited resources and access to capital to fund our operations, we must decide which product candidates to pursue and the amount of resources to allocate to each. In addition, for product candidates under development, such as NBTXR3, we must decide for which indications we intend to develop the product candidate for treatment. As such, we are currently primarily focused on the development of NBTXR3, particularly for the treatment of patients with locally advanced head and neck cancers. Our decisions concerning the allocation of research, collaboration, management and financial resources toward particular product candidates, oncological indications or therapeutic areas may not lead to the development of viable commercial products and may divert resources away from other more promising opportunities. Similarly, our potential decisions to delay, terminate or collaborate with third parties with respect to some of our product development programs may also prove not to be optimal and could cause us to miss valuable opportunities. If we do not accurately evaluate the commercial potential or target market for a particular product candidate, we may relinquish valuable rights to that product candidate through collaboration, licensing or other arrangements in cases in which it would have been more advantageous for us to retain sole development and commercialization rights. If we make incorrect determinations regarding the market potential of our product candidates or misread trends in the field of cancer treatment, our business prospects could be harmed.

The process of developing our product candidates is expensive, lengthy and risky. We expect our research and development expenses to increase substantially as we continue to develop NBTXR3 through our clinical development programs and identify new product candidates for development. Further, as a result of our increasing commercialization efforts with respect to NBTXR3 and the costs of operating as a U.S. public company, our selling, general and administrative expenses will increase significantly in the next several years.

As of September 30, 2020, we had cash and cash equivalents of €42.4 million. We believe our cash and cash equivalents, together with the net proceeds from the offering, will be sufficient to fund our operations through the end of 2022. However, in order to continue our ongoing research and development efforts, pursue regulatory approval and certification, and advance our commercialization efforts, we will require substantial additional funding. Also, our operating plan, including our product candidate development plans, may change as a result of many factors currently unknown to us, and we may need to seek additional funds sooner than planned, through public or private equity or debt

financings, government or other third-party funding, marketing and distribution arrangements and other strategic alliances and licensing arrangements, or a combination of these approaches.

To the extent that we raise additional capital through the sale of additional equity or convertible securities, your ownership interest may be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect your rights as a shareholder. Debt financing, if available, would result in increased fixed payment obligations and a portion of our operating cash flows, if any, being dedicated to the payment of principal and interest on such indebtedness. In addition, debt financing may involve agreements that include restrictive covenants that impose operating restrictions, such as restrictions on the incurrence of additional debt, the making of certain capital expenditures or the declaration of dividends. To the extent that we raise additional funds through arrangements with research and development partners or otherwise, we may be required to relinquish some of our technologies, product candidates or revenue streams, license our technologies or product candidates on unfavorable terms, or otherwise agree to terms unfavorable to us. Any additional fundraising efforts may divert our management’s attention from their day-to-day activities, which may adversely affect our ability to develop and commercialize our product candidates. In addition, we cannot guarantee that future financing will be available in sufficient amounts or on terms acceptable to us, if at all. Even if we believe we have sufficient funds for our current or future operating plans, we may seek additional capital if market conditions are favorable or in light of specific strategic considerations.

If we are unable to obtain funding on a timely basis, our growth prospects could be impaired, the price of our ordinary shares and ADSs may decline, and we may be required to, among other things:

The Finance Contract governing the EIB loan contains covenants that impose restrictions on the operation of our business. For example, without the approval of the European Investment Bank (“EIB”), the restrictions in the Finance Contract limit our and our subsidiaries’ ability, among other things, to:

As a result of these covenants and restrictions, we are limited in how we conduct our business. Although the restrictions in the Finance Contract contain several exceptions and carve-outs and may be waived by EIB, as a result of the restrictions we may be unable to raise additional financing after this offering or pursue new business opportunities that we believe would be beneficial to our business objectives.

In order to obtain requisite regulatory approvals and to successfully complete the necessary conformity assessment procedures, as applicable, we conduct preclinical and clinical programs for our product candidates with the goal of ultimately marketing therapeutic solutions to transform cancer treatments that utilize radiotherapy. NBTXR3, our lead product candidate, is currently being evaluated in a total of eight clinical trials worldwide as a potential treatment in various cancer indications. In January 2019 we announced a collaboration with MD Anderson which provides for approximately 340 patients to be enrolled across a total of nine clinical trials to be conducted in the United States to evaluate NBTXR3 across several cancer types. Because we are conducting clinical trials for NBTXR3 in multiple cancer indications, an unfavorable outcome in one or more trials may call into question the safety or efficacy in trials with respect to other cancer indications, and potentially undermine the validity of our nanotechnology platform.

Further, preclinical testing and clinical trials are long, expensive and unpredictable processes that can encounter extensive delays. We cannot guarantee that any clinical trials will be conducted as planned or completed on schedule, if at all. For example, one patient who participated in our clinical trial evaluating NBTXR3 in patients with late-stage cancers died from his cancer before any observation of response to treatment. Although this death was determined to be unrelated to the treatment, such setbacks could cause delays in our clinical trials. It may take several years to complete the preclinical testing and clinical development necessary to commercialize a product candidate, and delays or failure can occur at any stage. The design of a clinical trial can determine whether its results will support approval and certification of a product, as applicable, and flaws in the design of a clinical trial may not become apparent until the clinical trial is well advanced. An unfavorable outcome in one or more trials would be a major setback for our product candidates and for us. Due to our limited financial resources, an unfavorable outcome in one or more trials may require us to delay, reduce the scope of, or eliminate one or more product development programs, which could have a material adverse effect on our business and financial condition and on the value of our ordinary shares or ADSs.

In connection with clinical testing and trials, we face a number of risks, including risks that:

The results of preclinical studies do not necessarily predict clinical success, and larger and later-stage clinical trials may not produce the same results as earlier-stage clinical trials. To date, clinical trials of NBTXR3 in certain oncological indications have generated favorable data; however, we may have different enrollment criteria in our future clinical trials and certain clinical trials have only yielded preliminary data. As a result, we may not observe similar results as in our prior clinical trials or in our preliminary data. Frequently, product candidates developed by pharmaceutical, biopharmaceutical and nanomedicine companies have shown promising results in preclinical studies or early clinical trials, but have subsequently suffered significant setbacks or failed in later clinical trials. Further, clinical trials of potential products often reveal that it is not possible or practical to continue development efforts for these product candidates.

We cannot guarantee that our current or future product development efforts will be successful, or completed within our anticipated time frames. If we do not successfully complete preclinical and clinical development, we will be unable to pursue required market authorization to market and sell our product candidates and generate revenues. Even if we do successfully complete clinical trials, those results are not necessarily predictive of results of additional trials that may be needed before submitting marketing applications to the FDA, or initiating necessary conformity assessment procedures, as applicable. Although there are a large number of drugs and medical devices in development in Europe, the United States and other countries, only a small percentage result in the submission of a marketing application or the initiation of a conformity assessment procedure, even fewer are approved for commercialization, and only a small number achieve widespread physician and consumer acceptance following regulatory approval or successful completion of the conformity assessment procedure, as applicable. If our clinical trials are substantially delayed or fail to prove the safety and effectiveness of our product candidates in development, we may not successfully complete applicable pre-marketing regulatory requirements for any of these product candidates and our business and financial condition will be materially harmed.

Human clinical trials are very expensive, time-consuming, and difficult to design, implement and complete. Commencement of our clinical trials for our product candidates may be delayed for a variety of reasons, including delays in:

The completion of our clinical trials for our product candidates may be delayed, suspended or terminated due to a number of factors, including:

Many of these factors could also ultimately lead to the denial of our marketing application or the failure to complete applicable pre-marketing regulatory requirements for NBTXR3, or our other product candidates. If we experience delays, suspensions or terminations in a clinical trial, the commercial prospects for the related product candidate will be harmed, and our ability to generate product revenues will be delayed or such revenues could be reduced or fail to materialize.

We currently, and expect to continue to, depend on collaborations with public and private research institutions, including hospitals, clinics and cancer treatment centers, to conduct some of our development activities. If we are unable to enter into research collaborations with these institutions, or if any one of these institutions fails to work efficiently with us, the research, development or marketing of our product candidates planned as part of the collaboration could be delayed or canceled. In the event a collaboration agreement is terminated or we become unable to renew the arrangement under acceptable conditions, our discovery and development activities may also be delayed.

Further, we depend on our production method, which we developed internally, for the manufacturing of nanoparticles. Although we have trained our third-party manufacturers in the application of our production method (and seek to maintain quality control through, among other things, implementation of a monitoring system), we do not control such third-party manufacturers’ implementation of our production methods. In addition, we cannot provide any assurance that such third-party manufacturers will comply with all necessary safety protocols with respect to the implementation of our production method. Any interruption in the production of nanoparticles using the production method, including due to injuries or safety concerns from the implementation thereof, could significantly compromise our product development efforts.

We rely, or may rely, on medical institutions, clinical investigators and contract collaborators to carry out our clinical trials and to perform data collection and analysis. For example, under our primary collaboration agreement, one NBTXR3 clinical trial is currently being run by MD Anderson, and MD Anderson is expected to serve as the sponsor for the other eight clinical trials we expect to launch as part of this collaboration. In addition, pursuant to the License and Collaboration Agreement with PharmaEngine, three NBTXR3 clinical trials are currently being run in Asia by PharmaEngine, although, as described in this prospectus, in the event of a dispute with PharmaEngine, we may not be able to progress these trials beyond their current stage. See “Business—Collaborations and Research Agreements.”

Our clinical trials conducted in reliance on third parties may be delayed, suspended, or terminated if:

We generally do not have the ability to control the performance of third parties in their conduct of clinical trials and data collection and analysis. Third-party performance failures may increase our development costs, delay our ability to obtain regulatory approval or successfully complete pre-marketing certification procedures, and delay or prevent the commercialization of our product candidates. In addition, our third-party agreements usually contain a clause limiting such third party’s liability, such that we may not be able to obtain full compensation for any losses we may incur in connection with the third party’s performance failures. Ultimately, we remain responsible for ensuring that each of our clinical trials is conducted in accordance with the applicable protocol, legal, regulatory and scientific standards, and our reliance on third parties does not relieve us of this responsibility. While we believe that in many cases there are alternative sources to provide these services, in the event that we seek such alternative sources, we may not be able to

enter into replacement arrangements without incurring delays or additional costs. Further, in the event of a default, bankruptcy or shutdown of, or a dispute with, a third party, we may be unable to enter into a new agreement with another third party on commercially acceptable terms.

We have limited capabilities for product development and may seek to enter into collaborations with third parties for the development and potential commercialization of our product candidates. Should we seek to collaborate with a third party with respect to a prospective development program, we may not be able to locate a suitable collaborator and may not be able to enter into an agreement on commercially reasonable terms or at all. Even if we succeed in securing collaborators for the development and commercialization of our product candidates, such as our existing collaboration arrangements, we have limited control over the amount and timing that our collaborators may dedicate to the development or commercialization of our product candidates. These collaborations pose a number of risks, including the following:

Thus, collaboration agreements may not lead to development or commercialization of product candidates in the most efficient manner or at all.

We also face competition in seeking out collaborators. If we are unable to secure new collaborations that achieve the collaborator’s objectives and meet our expectations, we may be unable to advance our product candidates and may not generate meaningful revenues.

Our collaboration agreements, and those we may enter into in the future, generally require that our collaboration partners use commercially reasonable efforts to advance the development and/or potential commercialization of our product candidates for certain indications and in specified geographies, typically in accordance with a jointly approved development plan. Such collaboration agreements generally include dispute resolution procedures, which permit both us and our collaboration partners to terminate the collaboration under certain circumstances, including upon any uncured material breach of the agreement. The failure of any collaboration partner to fulfill its obligations under a collaboration agreement may result in delays in clinical trial activities or the discontinuation of clinical trials sponsored and conducted by our collaboration partner, which could limit the geographies in which we are able to effectively develop and commercialize our product candidates. Early termination of any collaboration agreement could result in additional costs and the loss of potential revenue opportunities. In addition, early termination of any collaboration agreement could result in disputes over intellectual property rights, responsibility for incurred costs or rights with respect to future revenue, which could lead to arbitration, litigation or other dispute resolution mechanisms. Disputes or litigation involving a collaboration partner may make it difficult for us to enter into a new agreement with another third party on commercially acceptable terms.

In 2012, we entered into an exclusive license and collaboration agreement with PharmaEngine for the development and potential commercialization of NBTXR3 in the Asia-Pacific region. We believe that PharmaEngine has not complied with its obligations under the License and Collaboration Agreement to use commercially reasonable efforts to develop NBTXR3 in this region. Accordingly, we have notified PharmaEngine of this material breach and, in accordance with the

requirements of the License and Collaboration Agreement, have requested that PharmaEngine cure such default. If PharmaEngine does not cure such default within 90 days of our notice, we believe that we are entitled to terminate the License and Collaboration Agreement on this basis. In a letter dated December 1, 2020, PharmaEngine responded to our notification of material breach, denying a material breach of the License Agreement and asserting certain material breaches of that agreement by us. Unless an appropriate resolution is reached with PharmaEngine, these trials may not progress beyond their current stage. If we terminate the agreement, the eventual development and commercialization of NBTXR3 in the Asia-Pacific region could be delayed, unless we are able to identify and enter into a definitive agreement with a new collaborator for this region. We may also incur additional costs and expenses relating to any potential dispute with PharmaEngine and the development and potential commercialization of NBTXR3 in the Asia-Pacific region if we terminate the collaboration with PharmaEngine.

The development and commercialization of therapeutic solutions for cancer treatment are governed by a rigorous, complex and evolving global regulatory environment. Regulatory authorities, including the FDA in the United States, have imposed stringent requirements on the amount and types of data required to demonstrate the safety and efficacy of products prior to marketing and sale. Moreover, any products approved for commercialization are reassessed in terms of their patient risk/benefit ratio on a regular basis following initial approval or certification. The late discovery of issues or potential problems which were not detected during development and clinical trials can result in restrictions on sale, the suspension or withdrawal of the product from the market and an increased risk of litigation. Given that extensive global regulation has increased the cost of obtaining and maintaining the necessary marketing authorizations and the cost of successfully completing the necessary conformity assessment procedures, for therapeutic oncology solutions, and therefore may limit the economic value of a new product, the prospects for growth in this field, and for our product candidates, have been reduced.

In addition, clinical studies for our product candidates are subject to prior submission requirements to the relevant regulatory authorities of the countries in which the studies will be carried out. For example, in the United States, a clinical study may proceed once the FDA notifies the applicant that the study may proceed or after 30 days if the submission is not placed on hold by the FDA. A negative opinion from such a regulatory authority with respect to any of our clinical development programs could suspend or terminate such programs. Moreover, depending on the information provided to regulatory authorities during a clinical trial pursuant to ongoing reporting requirements, particularly about the occurrence of undesirable side effects, the regulatory authorities could decide to prematurely suspend or terminate the clinical trial.

NBTXR3 has been classified as a “Class III medical device” in the EU and as a “drug” in the United States. Independent certification organizations (“Notified Bodies”) designated by the national EU Member States, the FDA in the United States and comparable regulatory authorities in other jurisdictions must approve or certify the conformity of, as applicable, new drug or high risk medical device candidates before they can be commercialized, marketed, promoted or sold in those jurisdictions. We must provide these regulatory authorities with data from preclinical studies and clinical trials that demonstrate that our product candidates are safe and effective for a defined indication before they can be approved or certified for commercial distribution. We must provide data to ensure the strength, quality and purity of the substance and product. We must also assure the regulatory authorities that the characteristics and performance of the clinical batches will be replicated consistently in the commercial batches.

The competent authorities of EU Member States could reconsider the classification of NBTXR3 as a medical device in the EU and decide to reclassify it as a “drug.” If our product candidates were to be classified as drugs in the EU, their clinical development would become subject to a more complex regulatory framework and the development and commercialization process would therefore be longer and more costly than expected under the current medical device classification. In an effort to minimize the impact of a potential reclassification of our product candidates, we currently conduct our clinical trials in accordance with the regulatory framework required for product candidates designated as drugs.

As of the date of this prospectus, we are primarily focusing our development and planned commercialization efforts on the EU and the United States, and to a lesser extent, Asia. Although we achieved a proof-of-concept in 2019 when we completed the regulatory process for the CE mark of NBTXR3, thereby allowing the product to be commercialized in the 27 EU countries for the treatment of locally advanced STS in the EU, we are now prioritizing the development of NBTXR3 in the United States and the EU for the treatment of head and neck cancers. We cannot assure you that NBTXR3, or any of our future product candidates, will receive approval from the FDA or any other regulatory authority, or will successfully complete conformity assessment procedures in the EU. Our April 2019 CE marking for Hensify^® does not provide any assurance that additional NBTXR3 product candidates will successfully complete similar regulatory procedures. Even if we successfully complete applicable pre-marketing regulatory requirements for any of our product candidates in a major market such as the United States or the EU, we may never obtain approval or commercialize our products in other major markets, due to varying approval procedures or otherwise, which would limit our ability to realize their full market potential.

Several factors will determine whether we receive FDA approval or whether we successfully complete the conformity assessment procedures in the EU, including, but not limited to:

In the event that we do not successfully complete applicable pre-marketing regulatory requirements for our product candidates established by the applicable authorities or bodies in our target jurisdictions, we will be unable to commercialize such candidates.

Our ability to commercialize any products successfully also will depend in part on the extent to which coverage and adequate reimbursement for these products and related treatments will be available from third-party payors, including government health administration authorities, private health insurers, health maintenance organizations and other organizations. Third-party payors determine which therapeutic treatments they will cover and establish reimbursement levels. Assuming we obtain coverage for a given product by a third-party payor, the resulting reimbursement payment rates may not be adequate or may require co-payments that patients find unacceptably high. Patients are unlikely to use our products unless coverage is provided and reimbursement is adequate to cover all or a significant portion of the cost of our products and the treatment associated with use of our products. Therefore, coverage and adequate reimbursement is critical to new product acceptance. Coverage decisions may depend upon clinical and economic standards that disfavor new drug products when more established or lower cost therapeutic alternatives are already available or subsequently become available.

Third-party payors are developing increasingly sophisticated methods of controlling healthcare costs, such as by limiting coverage and the amount of reimbursement for particular therapeutic treatments. Increasingly, third-party payors are requiring that healthcare companies provide them with predetermined discounts from list prices as a condition of coverage, are deploying various techniques to leverage greater discounts in competitive classes, and are challenging the prices charged for therapeutic products. In addition, in the United States, federal programs impose penalties on drug manufacturers in the form of mandatory additional rebates and/or discounts if commercial prices increase at a rate greater than the Consumer Price Index-Urban, and these rebates and/or discounts, which can be substantial, may impact our ability to raise commercial prices. Further, no uniform policy requirement for coverage and reimbursement for drug products exists among third-party payors in the United States. Therefore, coverage and reimbursement for drug products can differ significantly from payor to payor. As a result, the coverage determination process is often a time-consuming and costly process that will require us to provide scientific and clinical support for the use of our products to each payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance.

The continuing efforts of third-party payors to contain or reduce costs of healthcare may negatively affect our commercialization prospects, including:

We cannot be sure that coverage and reimbursement will be available for any potential product candidate that we may commercialize and, if reimbursement is available, what the level of reimbursement will be. Coverage and reimbursement may impact the demand for, or the price of, any product candidate for which we successfully complete applicable pre-marketing regulatory requirements. If coverage and reimbursement are not available or reimbursement is available only to limited levels, we may not successfully commercialize any product candidate for which we successfully complete applicable pre-marketing regulatory requirements.

In the United States, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act (collectively, the “ACA”) has significantly impacted, and will continue to impact, the provision of, and payment for, healthcare. Various provisions of the ACA were designed to expand Medicaid eligibility, subsidize insurance premiums, provide incentives for businesses to provide healthcare benefits, prohibit denials of coverage due to pre-existing conditions, establish health insurance exchanges, and provide additional support for medical research. With regard to therapeutic products specifically, the ACA, among other things, expanded and increased industry rebates for drugs covered under Medicaid programs and made changes to the coverage requirements under the Medicare prescription drug benefit.

Since its enactment there have been judicial and legislative challenges to certain aspects of the ACA, as well as efforts by the Trump administration to repeal or replace certain aspects of the ACA. In May 2018, the Trump Administration published its American Patients First proposal, which indicates its plans to investigate the ACA’s impact on private market drug prices and potentially alter the ACA taxes and rebates for Medicaid and Medicaid managed care organizations. On December 14, 2018, a federal judge for the Northern District of Texas, Fort Worth Division, issued a ruling declaring the ACA unconstitutional. On December 18, 2019, the Fifth Circuit Court of Appeals affirmed pertinent aspects of the decision but remanded to the Northern District of Texas the decision as to whether the remainder of the ACA is valid. It is unclear how this decision, subsequent appeals, and other efforts to repeal and replace the ACA will impact the ACA and ability to market any product candidates.

In addition to further judicial review of the ACA, the Trump administration and other United States federal and state officials are continuing to focus on the cost of health coverage, health care and pharmaceuticals although future policy or the timing of any changes remains unclear, creating significant risks for the sector. At the federal level, legislation like the Bipartisan Budget Act of 2018 amended the ACA, effective January 1, 2019, to close the coverage gap in most Medicare drug plans, and also increased in 2019 the percentage by which a drug manufacturer must discount the cost of prescription drugs from 50 percent under current law to 70 percent.

In addition, both the Budget Control Act of 2011 and the American Taxpayer Relief Act of 2012 (the “ATRA”), have instituted, among other things, mandatory reductions in Medicare payments to certain providers.

Further, there has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several recent U.S. Congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to drug pricing, review the relationship between pricing and manufacturer patient programs, reduce the costs of drugs under Medicare and reform government program reimbursement methodologies for drug products. Federal regulatory reform intended to reduce costs of drugs furnished under Medicare and Medicare Advantage plans through utilization management tools, like step therapy, and to increase price transparency for such drugs through the prohibition of gag clauses in pharmacy contracts became effective on January 1, 2020. Since 2017, at least nine states enacted and an additional 25 states proposed legislation which will require price transparency and reporting of certain manufacturer information. This trend is anticipated to continue, where legislation is expected regarding pricing transparency, marketing, access to drugs and other measures related to pricing.

On January 31, 2019, the U.S. Department of Health and Human Services, Office of Inspector General, proposed modifications to the U.S. federal Anti-Kickback Statute discount safe harbor for the purpose of reducing the cost of drug products to consumers which, among other things, if finalized, will affect discounts paid by manufacturers to Medicare Part D plans, Medicaid managed care organizations and pharmacy benefit managers working with these organizations. Although a number of these, and other proposed measures may require authorization through additional legislation to become effective, Congress and the Trump administration have each indicated that it will continue to seek new legislative and/or administrative measures to control drug costs. These legislative proposals and initiatives could harm our ability to market any product candidates and generate revenues.

We expect that the ACA, as well as other healthcare reform measures that may be adopted in the future, may result in more rigorous coverage criteria and lower reimbursement, and in additional downward pressure on the price that we receive for any approved product candidate. Any reduction in reimbursement from Medicare or other government-funded programs may result in a similar reduction in payments from private payors. Additionally, the United States market has been further consolidated by key private payor organizations. For instance, CVS-Aetna and Cigna-ESI mergers highlight the role of integrated payor arrangements, including PBMs, which impacts product access and affordability. Such market consolidation may further impact market pricing in the future (three PBMs now cover over 75% of the market resulting in significant negotiating power for commercial and Medicare Part D plans). Both government and commercial payors are aggressively pursuing and implementing cost containment tools designed to lower plan-level net costs. Further, the United States Congress continues to focus on pharmaceutical pricing with bipartisan support. While the United States House-passed legislation (H.R. 3) is unlikely to become law in 2020, given Senate Republican opposition, both Democrats and Republicans have prioritized legislative agendas and policies to enact reform that lowers out-of-pocket expenses so additional legislative focus from state and federal bodies is anticipated. The potential implementation of further pricing practice scrutiny and related cost containment measures or other healthcare reforms may prevent us from being able to generate revenue, attain profitability or commercialize our products. Moreover, we cannot predict what healthcare reform initiatives may be adopted in the future.

In some foreign countries, the proposed pricing for a therapeutic product must be approved before it may be lawfully marketed. In addition, in some foreign markets, the pricing of therapeutic products is subject to government control and reimbursement may in some cases be unavailable. The requirements governing pricing of therapeutic products vary widely from country to country. For example, the EU provides options for its Member States to restrict the range of therapeutic products for which their national health insurance systems provide reimbursement and to control the prices of therapeutic products for human use. A Member State may approve a specific price for the therapeutic product, may refuse to reimburse a product at the price set by the manufacturer or may instead adopt a system of direct or indirect controls on the profitability of the company placing the therapeutic product on the market. There can be no assurance that any country that has price controls or reimbursement limitations for therapeutic products will allow favorable reimbursement and pricing arrangements for NBTXR3 or any of our other product candidates that may be approved. Historically, therapeutic products launched in the EU do not follow price structures of the United States and generally tend to have significantly lower prices.

The scope and nature of pricing controls vary country to country, but common themes include the following: reference pricing, systematic price reduction, formularies, volume limitations, patient copayment limitations, and generic substitution. In the United States and internationally, we believe that pricing pressures at multiple levels of government, including third party review of pricing practices, will continue and may increase, which may make it difficult for us to sell our potential product candidates that may be approved in the future at a price acceptable to us or any third parties with whom we may choose to collaborate.

Even if we successfully complete applicable pre-marketing regulatory requirements for the commercialization of a product candidate, the resulting approval or certification may carry conditions that limit the market for the product or put the product at a competitive disadvantage relative to alternative therapies. For instance, a regulatory approval may limit the indicated uses for which we can market a product or the patient population that may utilize the product.

These restrictions could make it more difficult to market the product effectively. Accordingly, assuming we successfully complete applicable pre-marketing regulatory requirements for the commercialization of any of our product candidates, we will continue to expend time, money and effort in all areas of regulatory compliance.

In February 2020, the FDA granted Fast Track designation for NBTXR3 activated by radiation therapy, with or without cetuximab, for the treatment of patients with locally advanced head and neck squamous cell cancer who are not eligible for platinum-based chemotherapy. If a product is intended for the treatment of a serious or life-threatening condition and the product demonstrates the potential to address unmet medical needs for that condition, the product sponsor may apply for FDA Fast Track designation. The FDA has broad discretion whether or not to grant this designation. Even though we have received Fast Track designation for NBTXR3, we may not experience a faster development process, review or approval compared to conventional FDA procedures. The FDA may withdraw a Fast Track designation if it believes that the designation is no longer supported by data from our clinical development program. Many products that have received Fast Track designation have failed to obtain approval from the FDA.

We do not currently have Breakthrough Therapy designation for any of our product candidates but may seek it in the future. A Breakthrough Therapy is defined as a product that is intended, alone or in combination with one or more other products, to treat a serious or life-threatening disease or condition, and preliminary clinical evidence indicates that the product may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. For products that have been designated as Breakthrough Therapies, interaction and communication between the FDA and the sponsor can help to identify the most efficient path for development.

Designation as a Breakthrough Therapy is within the discretion of the FDA. Accordingly, even if we believe, after completing early clinical trials, that one of our product candidates meets the criteria for designation as a Breakthrough Therapy, the FDA may disagree and instead decide not to grant that designation. In any event, the receipt of a Breakthrough Therapy designation for a product candidate may not result in a faster development process, review or approval compared to products considered for approval under conventional FDA procedures and does not assure ultimate approval by the FDA. In addition, even if one or more of our product candidates qualify as Breakthrough Therapies, the FDA may later decide that such product candidates no longer meet the conditions for qualification.

We are dependent on third parties for the supply of various materials that are necessary to produce our product candidates for clinical trials. See “Business—Manufacturing.” Although we have entered into agreements related to the supply of the raw materials used in the manufacturing of our nanoparticles, the supply could be reduced or interrupted at any time. In such case, we may not be able to find other suppliers of acceptable materials in appropriate quantities at an acceptable cost. If we lose key suppliers or the supply of materials is diminished or discontinued, or in the event of a major or international crisis impacting mining or the extraction of minerals in certain regions, we may not be able to continue to develop, manufacture and market our product candidates or products in a timely and competitive manner. In addition, these materials are subject to stringent manufacturing processes and rigorous testing. Delays in the completion and validation of facilities and manufacturing processes of these materials could adversely affect our ability to complete trials and commercialize our products in a cost-effective and timely manner. If we encounter difficulties in the supply of these materials, chemicals or other necessary products, or if we were not able to maintain our supply agreements or establish new supply agreements in the future, or incur increased production costs as a result of any of the foregoing, our product development and our business prospects could be significantly compromised.

In 2017, we opened our own manufacturing site near Paris that we expect will allow us to expand our production capacity to more than 200,000 doses of NBTXR3 per year—an amount that we believe will be sufficient for our current and contemplated clinical trials and the first few years following a commercial launch. However, we have not yet manufactured significant doses of NBTXR3 at this scale and may never be successful in developing manufacturing

capabilities sufficient to meet our clinical trial needs. Moreover, we may have more limited access to raw materials and other components necessary for the manufacturing of our product candidates than third-party manufacturers, who may have more established relationships with suppliers, greater financial resources than us, and/or the ability to leverage purchasing scale for more efficient pricing of raw materials. Our manufacturing facilities could be affected by cost-overruns, unexpected delays, equipment failures, labor shortages, natural disasters, power failures, regulatory issues and numerous other factors that could prevent us from realizing the intended benefits of our manufacturing strategy and have a material adverse effect on our business.

We contract the production of NBTXR3 for use in clinical trials to high-precision manufacturing partners. In addition, in 2017 we expanded our own manufacturing capabilities by opening an internal research and innovation center facility just outside of Paris, France. We and our third-party manufacturers are subject to ongoing regulation and periodic inspection by the national competent authorities of the EU Member States, FDA and other regulatory bodies to ensure current Good Manufacturing Practices (“cGMP”) and international organization for standards (“ISO”) compliance, as applicable. Any failure to follow and document our or their adherence to such cGMP regulations or other regulatory requirements may lead to significant delays in the availability of products for commercial sale or clinical trials, may result in the termination of or a hold on a clinical trial, or may delay or prevent filing or approval of marketing applications or the completion of pre-marketing certification procedures, as applicable, for our products.

Failure to comply with applicable regulations could also result in the FDA or other applicable regulatory authorities taking, or causing to be taken, various actions, including:

Any of the foregoing actions could be detrimental to our reputation, business, financial condition or operating results. Furthermore, our key suppliers may not continue to be in compliance with all applicable regulatory requirements, which could result in our failure to produce our products on a timely basis and in the required quantities, if at all. In addition, before any products would be considered for marketing in the United States, the EU or elsewhere, our suppliers will have to pass an audit by the applicable regulatory agencies. We are dependent on our suppliers’ cooperation and ability to pass such audits, and the audits and any audit remediation may be costly. Failure to pass such audits by us or any of our suppliers would affect our ability to commercialize our product candidates in the United States, the EU or elsewhere.

To date, we have the right to CE mark, and therefore to commercialize, on an accelerated basis, only one of our product candidates, Hensify^®, the brand name for NBTXR3 for the treatment of locally advanced STS. This does not mean any of our other product candidates will receive approval for commercialization or that Hensify^® will receive approval for commercialization in any other jurisdictions. In addition, even though we received approval for Hensify^® and even if we

receive additional approvals to commercialize any of our product candidates in the EU, the United States or elsewhere, we will need to gain the approval of the medical community, care prescribers and third party payors in order to achieve commercial success. Despite the fact that we have successfully completed all the regulatory steps allowing us to commercialize Hensify^® in Europe, we have not yet undertaken any commercialization activities. Following evaluation of the results from Studies 102 and 312, we intend to undertake a strategic review and to determine where we believe we are best positioned to pursue commercialization, including our commercialization strategy with respect to Hensify^®.

Even if the medical community accepts a product as safe and efficacious for its indicated use, physicians may choose to restrict the use of the product if we are unable to demonstrate that, based on experience, clinical data, side-effect profiles and other factors, our product is preferable to any alternative treatment methods. We cannot predict the degree of market acceptance of any product candidate that successfully completes applicable pre-marketing regulatory requirements, which will depend on a number of factors, including, but not limited to:

Even if our products are able to improve current therapeutic responses, poor market penetration, resulting from one or more of the factors listed above, could have a negative impact on our business prospects. Other product solutions which directly or indirectly compete with our products could also hinder our development efforts or render our products obsolete. Similarly, to the extent a cancer treatment method is shown to be more effective than, or were to displace, radiotherapy, our business would be adversely affected. Despite our best efforts, we cannot guarantee that the clinical development of our product candidates will result in successful completion of applicable pre-marketing regulatory requirements for commercialization, or that even if we do complete such requirements, that our products will be accepted by the market and experience commercial success.

Even if we successfully complete clinical trials for one or more of our product candidates and complete relevant regulatory requirements, those candidates may not be commercialized for other reasons, including:

Any of our product candidates for which we successfully complete applicable pre-marketing regulatory requirements for commercialization, such as CE marking for NBTXR3 for the treatment of locally advanced STS in the EU, as well as the manufacturing processes, post-approval studies and measures, and labeling and promotional activities for such products, among other things, will be subject to continual requirements of and review by the Notified Body and national competent authorities of EU Member States, FDA and other regulatory authorities. These requirements include submissions of safety and other post-marketing information and reports, registration and listing requirements, requirements relating to manufacturing, quality control, quality assurance and corresponding maintenance of records and documents, requirements regarding the distribution of samples to physicians and recordkeeping. Even if we successfully complete applicable pre-marketing regulatory requirements for a product candidate, the resulting approval or certification, as applicable, may be subject to limitations on the indicated uses for which the product may be marketed or to the conditions of approval, including an FDA requirement to implement a risk evaluation and mitigation strategy to ensure that the benefits of a drug product outweigh its risks.

The FDA, and other regulatory bodies, may also impose requirements for costly post-marketing studies or clinical trials and surveillance to monitor the safety or efficacy of a product, such as long term observational studies. The FDA and other U.S. agencies, including the U.S. Department of Justice, closely regulate and monitor the post-approval marketing and promotion of therapeutic products to ensure that they are manufactured, marketed and distributed only for the approved indications and in accordance with the provisions of the approved labeling. The national competent authorities of EU Member States and FDA impose stringent restrictions on manufacturers’ communications regarding off-label use and if we do not limit the marketing of any of our product candidates to their approved indications, we may be subject to warnings or enforcement action for off-label marketing. Similarly, we cannot promote our products before completion of applicable pre-marketing regulatory requirements. Violation of the U.S. Federal Food, Drug and Cosmetic Act, and other related statutes, may lead to investigations or allegations of violations of federal and state health care fraud and abuse laws and state consumer protection laws.

We do not currently have a sales or marketing infrastructure and have no experience in the sale, marketing or distribution of drug or medical device products. We are currently prioritizing the development of NBTXR3 in the United States and the EU for the treatment of head and neck cancers. At such time as we pursue commercial sales with respect to an approved product candidate, we will have to quickly transition some of our resources and attention to marketing and developing a sales force, either internally or in coordination with strategic partners. We may enter into arrangements with partners for future marketing needs with respect to certain of our products, while also implementing our own sales and marketing organization with respect to other products. Such partners may not attain goals specified in agreements we enter into with them (including, for example, goals related to the timing of product commercialization, amount of sales and payment of milestones and royalties). There are risks involved with establishing our own sales, marketing and distribution capabilities. For example, recruiting and training a sales force is expensive and time-consuming and could delay any product launch. If the commercial launch of a product candidate for which we recruit a sales force and establish marketing capabilities is delayed or does not occur for any reason, we would have prematurely or unnecessarily incurred these commercialization expenses. This may be costly, and our investment would be lost if we cannot retain or reposition our sales and marketing personnel.

Factors that may inhibit our efforts to commercialize products on our own include:

If we are unable to establish our own sales, marketing and distribution capabilities and enter into arrangements with third parties to perform these services, our revenue and our profitability, if any, are likely to be lower than if we were to sell, market and distribute any products that we develop ourselves.

As of September 30, 2020, we had 90 full-time employees and we expect to increase our number of employees and expand the scope and location of our operations. In addition, as a U.S. public company following the offering, we will incur substantial additional legal, accounting and other expenses to comply with applicable SEC, Nasdaq and other rules and regulations. To manage our anticipated development, expansion and incurrence of additional expenses, including the development and potential commercialization of our product candidates, we must continue to implement and improve our managerial, operational and financial systems, expand our facilities and continue to recruit and train additional qualified personnel. Members of our management team may need to divert a disproportionate amount of their attention away from their day-to-day activities and devote a substantial amount of time to managing these development activities. Due to our limited resources, we may not be able to effectively manage the expansion of our operations or recruit and train additional qualified personnel. This may result in weaknesses in our infrastructure, give rise to operational mistakes, loss of business opportunities, loss of employees and reduced productivity among remaining employees. The physical expansion of our operations may lead to significant costs and may divert financial resources from other projects, such as the development of our product candidates. If our management is unable to effectively manage our expected development and expansion, our expenses may increase more than expected, our ability to generate or increase our revenue could be reduced and we may not be able to implement our business strategy. Our future financial performance and our ability to commercialize our product candidates, if approved, and compete effectively will depend, in part, on our ability to effectively manage the future development and expansion of our company.

Our success depends to a significant degree upon the technical skills and continued service of certain members of our management team, particularly Laurent Levy, Ph.D., our Chief Executive Officer. The loss of the services of any member of our management team could have a material adverse effect on us.

Our success will also depend upon our ability to attract and retain additional qualified management, regulatory, technical, and sales and marketing executives and personnel. The failure to attract, integrate, motivate, and retain additional skilled and qualified personnel could have a material adverse effect on our business. We compete for such personnel against numerous companies, including larger, more established companies with significantly greater financial resources than we possess. In addition, failure to succeed in our product candidates’ development may make it more challenging to recruit and retain qualified personnel. There can be no assurance that we will be successful in attracting or retaining such personnel and the failure to do so could have a material adverse effect on our business, financial condition and results of operations.

As a U.S. public company following the offering, we will incur legal, accounting and other expenses that we did not previously incur. We will be subject to the Exchange Act, including the reporting requirements thereunder, the Sarbanes-Oxley Act, the Dodd-Frank Wall Street Reform and Consumer Protection Act, the Nasdaq corporate governance requirements and other applicable securities laws, rules and regulations. Compliance with these laws, rules and regulations will increase our legal and financial compliance costs, make some activities more difficult, time-consuming or costly and increase demand on our systems and resources, particularly after we are no longer an emerging growth company.

Pursuant to Section 404 of the Sarbanes-Oxley Act, we will be required to furnish a report by our management on our internal control over financial reporting, including an attestation report on internal control over financial reporting issued by our independent registered public accounting firm. However, while we remain an emerging growth company, we will not be required to include this attestation report on internal control over financial reporting issued by our independent registered public accounting firm. When our independent registered public accounting firm is required to undertake an

assessment of our internal control over financial reporting, the cost of complying with Section 404 will significantly increase and management’s attention may be diverted from other business concerns, which could adversely affect our business and results of operations. We may need to hire more employees in the future or engage outside consultants to comply with these requirements, which will further increase our costs and expenses. If we fail to implement the requirements of Section 404 in the required timeframe, we may be subject to sanctions or investigations by regulatory authorities, including the SEC and Nasdaq. Furthermore, if we are unable to conclude that our internal control over financial reporting is effective, we could lose investor confidence in the accuracy and completeness of our financial reports, the market price of our ADSs could decline, and we could be subject to sanctions or investigations by regulatory authorities. Failure to implement or maintain effective internal control systems required of public companies could also restrict our future access to the capital markets. In addition, enhanced legal and regulatory regimes and heightened standards relating to corporate governance and disclosure for public companies result in increased legal and financial compliance costs and make some activities more time consuming.

We are exposed to the risk of employee fraud or other misconduct. Misconduct by employees could include intentional failures to comply with legal requirements or the requirements of the CMS, national competent authorities of EU Member States, FDA and other government regulators, provide accurate information to applicable government authorities, comply with fraud and abuse and other healthcare laws and regulations in the United States and abroad, report financial information or data accurately or disclose unauthorized activities to us. In particular, sales, marketing and business arrangements in the healthcare industry are subject to extensive laws and regulations intended to prevent fraud, misconduct, kickbacks, self-dealing and other abusive practices. These laws and regulations restrict or prohibit a wide range of pricing, discounting, marketing and promotion, sales commission, customer incentive programs and other business arrangements. Employee misconduct could also involve the improper use of, including trading on, information obtained in the course of clinical trials, which could result in regulatory sanctions and serious harm to our reputation. In connection with the offering, we intend to adopt a Code of Business Conduct and Ethics, but it is not always possible to identify and deter employee misconduct, and the precautions we take to detect and prevent this activity may be ineffective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to comply with these laws or regulations. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business, including the imposition of significant civil, criminal and administrative penalties, damages, fines, disgorgement, individual imprisonment, possible exclusion from government funded healthcare programs, such as Medicare and Medicaid, additional reporting requirements and oversight if subject to a corporate integrity agreement or similar agreement to resolve allegations of non-compliance with these laws, contractual damages, reputational harm, diminished profits and future earnings, and curtailment of our operations, any of which could substantially disrupt our operations.

Our research and development processes involve the controlled storage, handling, use and processing of hazardous materials (notably radioactive substances), including toxins and chemical agents. We cannot eliminate the risk of accidental contamination or discharge and any resultant injury from these materials. We may be sued for any injury or contamination that results from our use or the use by third parties of these materials, and our liability may exceed any insurance coverage and our total assets. EU and U.S. federal, state, local or other foreign laws and regulations govern the use, manufacture, storage, handling and disposal of these hazardous materials and specified waste products, as well as the discharge of pollutants into the environment and human health and safety matters. Compliance with environmental laws and regulations may be expensive and may impair our research and development efforts. If we fail to comply with these requirements, we could incur substantial costs, including civil or criminal fines and penalties, clean-up costs or capital expenditures for control equipment or operational changes necessary to achieve and maintain compliance. In addition, we cannot predict the impact on our business of new or amended environmental laws or regulations or any changes in the way existing and future laws and regulations are interpreted and enforced.

The risk that we may be sued on product liability claims is inherent in the development and commercialization of therapeutic products. Side effects of, manufacturing defects in, or improper physician administration of, products that we develop could result in the deterioration of a patient’s condition, injury or even death. For example, our liability could be sought after by patients participating in clinical trials due to unexpected side effects resulting from the administration of our products. Once a product successfully completes applicable pre-marketing regulatory requirements and is commercialized, the likelihood of product liability lawsuits increases. Criminal or civil proceedings might be filed against us by patients, physicians, regulatory authorities, pharmaceutical companies and any other third party using or marketing our products. These actions could include claims resulting from acts by our collaboration partners, potential licensees and subcontractors, over which we have little or no control. These lawsuits may divert our management from pursuing our business strategy and may be costly to defend. In addition, if we are held liable in any of these lawsuits, we may incur substantial liabilities and may be forced to limit or forgo further commercialization of the affected products. Any such adverse outcomes in future legal proceedings could also damage our market reputation which could in turn have an adverse effect on our ability to commercialize our products successfully.

We maintain product liability insurance coverage for our clinical trials at levels which we believe are appropriate for our clinical trials. Nevertheless, our insurance coverage may be insufficient to reimburse us for any expenses or losses we may suffer. In addition, in the future, we may not be able to obtain or maintain sufficient insurance coverage at an acceptable cost or to otherwise protect against potential product or other legal or administrative liability claims by us or our collaboration partners, licensees or subcontractors, which could prevent or inhibit the commercial production and sale of any of our product candidates that complete applicable pre-marketing regulatory requirements.

Healthcare providers, physicians and others will play a primary role in the recommendation, and the incorporation into treatment regimes, of our products, if approved and duly CE-marked. Our business operations in the United States and our arrangements with clinical investigators, healthcare providers, consultants, third-party payors and patients expose us to broadly applicable federal and state fraud and abuse and other healthcare laws. These laws may impact, among other things, our research, proposed sales, marketing and education programs of our product candidates that successfully complete applicable pre-marketing regulatory requirements. Restrictions under applicable U.S. federal, state and foreign healthcare laws and regulations include, but are not limited to, the following:

Ensuring that our business arrangements with third parties comply with applicable healthcare laws and regulations will likely be costly. It is possible that governmental authorities will conclude that our business practices do not comply with current or future statutes, regulations or case law involving applicable fraud and abuse or other healthcare laws and regulations. If our operations are found to be in violation of any of these laws or any other governmental regulations that may apply to us, we may be subject to significant civil, criminal and administrative penalties, damages, fines, disgorgement, individual imprisonment, possible exclusion from government funded healthcare programs, such as Medicare and Medicaid, additional reporting requirements and oversight if we become subject to a corporate integrity agreement or similar agreement to resolve allegations of non-compliance with these laws, contractual damages, reputational harm, diminished profits and future earnings, and curtailment of our operations, any of which could substantially disrupt our operations. If the physicians or other providers or entities with whom we expect to do business are found not to be in compliance with applicable laws, they may be subject to criminal, civil or administrative sanctions, including exclusions from government funded healthcare programs.

Our commercial success depends, in part, on obtaining and maintaining proprietary rights to our and our licensors’ intellectual property as well as successfully defending these rights against third-party challenges. We will only be able to protect our products, product candidates, processes and technologies from unauthorized use by third parties to the extent that valid and enforceable patents, or effectively protected trade secrets, cover them. Our ability to obtain patent protection for our products, product candidates, processes and technologies is uncertain due to a number of factors, including:

Even if we have or obtain patents covering our products, product candidates, processes and technologies, we may still be barred from making, using and selling our products, product candidates, processes and technologies because of the patent rights of others. Others may have filed, and in the future may file, patent applications covering products, product candidates, processes or technologies that are similar or identical to ours. Numerous U.S. and foreign issued patents and pending patent applications owned by others exist in the cancer treatment field in which we are developing products. These could materially affect our ability to develop and commercialize our product candidates or sell our products if approved. Because patent applications can take many years to issue, there may be currently pending applications unknown to us that may later result in issued patents that our products, product candidates, processes or technologies may infringe. These patent applications may have priority over patent applications filed by us or our licensors. Patent applications in France are only published 18 months after their priority date. In the United States, some patent applications are not published until the grant of the patent itself.

Obtaining and maintaining a patent portfolio entails significant expense and resources. Part of the expense includes periodic maintenance fees, renewal fees, annuity fees, various other governmental fees on patents and/or applications due over the course of several stages over the lifetime of patents and/or applications, as well as the cost associated with complying with numerous procedural provisions during the patent application process. We or our licensors may or may not choose to pursue or maintain protection for particular inventions. In addition, there are situations in which failure to make certain payments or noncompliance with certain requirements in the patent process can result in abandonment or lapse of a patent or patent application, resulting in partial or complete loss of patent rights in the relevant jurisdiction. If we choose to forgo patent protection or allow a patent application or patent to lapse purposefully or inadvertently, our competitive position could suffer.

Legal actions to enforce our patent rights can be expensive and may involve the diversion of significant management time. In addition, these legal actions could be unsuccessful and could also result in the invalidation of our patents or a finding that they are unenforceable. We may or may not choose to pursue litigation or other actions against those that have infringed on our patents, or used them without authorization, due to the associated expense and time commitment of monitoring these activities. If we fail to protect or to enforce our intellectual property rights successfully, our competitive position could suffer, which could harm our results of operations.

In addition to patent protection, because we operate in the highly technical field of the development of therapies using nanotechnology, we rely in part on trade secret protection in order to protect our proprietary technology and processes. However, trade secrets are difficult to protect. Monitoring unauthorized uses and disclosures is difficult, and we do not know whether the steps we have taken to protect our proprietary technologies will be effective. We cannot guarantee that our trade secrets and other proprietary and confidential information will not be disclosed or that competitors will not otherwise gain access to our trade secrets. We enter into non-disclosure agreements with our employees, consultants, outside collaborators, sponsored researchers and other advisors. These agreements generally require that the other party keep confidential and not disclose to third parties all confidential information developed by the party or made known to the party by us during the course of the party’s relationship with us. Despite these efforts, any of these parties may breach the agreements and disclose our proprietary information, including our trade secrets, and we may not be able to obtain adequate remedies for such breaches. These agreements also generally provide that inventions conceived by the party in the course of rendering services to us will be our exclusive property. However, these agreements may be breached or held unenforceable and may not effectively assign intellectual property rights to us. In particular, such parties may enter into other agreements with third parties and we would have no control over such contractual relationships and how they protect our confidential information.

In addition to contractual measures, we try to protect the confidential nature of our proprietary information using physical and technological security measures. Such measures may not provide adequate protection for our proprietary information. For example, our security measures may not prevent an employee or consultant with authorized access from misappropriating our trade secrets and providing them to a competitor, and the recourse we have available against such misconduct may not provide an adequate remedy to protect our interests fully. Enforcing a claim that a party illegally disclosed or misappropriated a trade secret can be difficult, expensive and time consuming, and the outcome is unpredictable. In addition, courts outside the United States may be less willing to protect trade secrets. Furthermore, our proprietary information may be independently developed by others in a manner that could prevent legal recourse by us. If any of our confidential or proprietary information, including our trade secrets, were to be disclosed or misappropriated, or if any such information was independently developed by a competitor, our competitive position could be harmed and our business could be materially and adversely affected.

The patent positions of companies developing oncology therapeutic solutions, including pharmaceutical and nanomedicine companies and other actors in our fields of business, can be highly uncertain and typically involve complex scientific, legal and factual analyses. In particular, the interpretation and breadth of claims allowed in some patents covering therapeutic compositions may be uncertain and difficult to determine, and are often affected materially by the facts and circumstances that pertain to the patented compositions and the related patent claims. The standards of the United States Patent and Trademark Office (the “USPTO”) and foreign patent offices are sometimes uncertain and could change in the future. Consequently, the issuance and scope of patents cannot be predicted with certainty. Patents, if issued, may be challenged, invalidated, narrowed or circumvented. U.S. patents and patent applications may also be subject to interference proceedings, and U.S. patents may be subject to reexamination proceedings, post-grant review, inter partes review, or other administrative proceedings in the USPTO. Foreign patents as well may be subject to opposition or comparable proceedings in corresponding foreign patent offices. Challenges to our patents and patent applications or our licensors’ patents and patent applications, if successful, may result in the denial of our patent applications or our licensors’ patent applications or the loss or reduction in their scope. In addition, such interference, reexamination, post-grant review, inter partes review, opposition proceedings and other administrative proceedings may be costly and involve the diversion of significant management time. Accordingly, rights under any of our patents or our licensors’ patents may not provide us with sufficient protection against competitive products or processes and any loss, denial or reduction in scope of any of such patents and patent applications may have a material adverse effect on our business.

Furthermore, even if not challenged, our patents and patent applications or our licensors’ patents and patent applications may not adequately protect our product candidates, processes or technologies or prevent others from designing their products or technology to avoid being covered by our patent claims or our licensors’ patent claims. If the breadth or strength of protection provided by the patents we own or license with respect to our products, product candidates, processes or technologies is threatened, it could dissuade companies from partnering with us to develop, and could threaten our ability to successfully commercialize, our product candidates, processes and technologies. Furthermore, for

U.S. patent applications in which claims are entitled to a priority date before March 16, 2013, an interference proceeding can be provoked by a third party or instituted by the USPTO in order to determine who was the first to invent any of the subject matter covered by such patent claims.

In addition, changes in, or different interpretations of, patent laws in the United States and other countries may permit others to use our discoveries or to develop and commercialize our products, product candidates, processes and technologies without providing any notice or compensation to us, or may limit the scope of patent protection that we or our licensors are able to obtain. The laws of some countries do not protect intellectual property rights to the same extent as U.S. laws and those countries may lack adequate rules and procedures for defending our intellectual property rights.

If we or our licensors fail to obtain and maintain patent protection and trade secret protection of our products, product candidates, processes and technologies, we could lose our competitive advantage and competition we face would increase, potentially reducing revenues and having a material adverse effect on our business.

Patents have a limited lifespan. Individual patent terms extend for varying periods of time, depending upon the date of filing of the patent application, the date of patent issuance, and the legal term of patents in the countries in which they are obtained. In the United States, the natural expiration of a patent is generally 20 years after its first effective filing date. In addition, although upon issuance in the United States a patent’s life can be increased based on certain delays caused by the USPTO, this increase can be reduced or eliminated based on certain delays caused by the patent applicant during patent prosecution. However, the actual protection afforded by a patent varies on a product-by-product basis, from country-to-country, and depends upon many factors, including the type of patent, the scope of its coverage, the availability of legal remedies in a particular country, and the validity and enforceability of the patent. If we or our licensors do not have sufficient patent life to protect our products, processes and technologies, our business and results of operations will be adversely affected.

Depending upon the timing, duration and conditions of FDA marketing approval of our product candidates, one or more of our U.S. patents may be eligible for limited patent term extension under the Drug Price Competition and Patent Term Restoration Act of 1984, referred to as the Hatch-Waxman Amendments. The Hatch-Waxman Amendments permit a patent term extension of up to five years for a patent covering an approved product as compensation for effective patent term lost during product development and the FDA regulatory review process. However, we may not receive an extension if we fail to apply within applicable deadlines, fail to apply prior to expiration of relevant patents or otherwise fail to satisfy applicable requirements. Moreover, the length of the extension could be less than we request. If we are unable to obtain patent term extension or the term of any such extension is less than we request, the period during which we can enforce our patent rights for that product will be shortened and our competitors may obtain approval to market competing products sooner. As a result, our revenue from applicable products could be reduced, possibly materially.

Filing, prosecuting and defending patents on our products, product candidates, processes and technologies in all countries and jurisdictions throughout the world would be prohibitively expensive, and our intellectual property rights in some countries outside the United States could be less extensive than those in the United States, assuming that rights are obtained in the United States. Competitors may use our technologies in jurisdictions where we or our licensors do not pursue and obtain patent protection to develop their own products and further, may export otherwise infringing products to territories where we or our licensors have patent protection, but where the ability to enforce our or our licensors’ patent rights is not as strong as in the United States. These products may compete with our products and our patents or other intellectual property rights may not be effective or sufficient to prevent such competition. Even if we pursue and obtain issued patents in particular jurisdictions, our patent claims or other intellectual property rights may not be effective or sufficient to prevent third parties from so competing.

In addition, the laws of some foreign countries do not protect intellectual property rights to the same extent as the federal and state laws in the United States. Patent protection must be sought on a country-by-country basis, which is an expensive and time-consuming process with uncertain outcomes. Accordingly, we and our licensors may choose not to seek patent protection in certain countries, and we will not have the benefit of patent protection in such countries. In

addition, the legal systems of some countries, particularly developing countries, do not favor the enforcement of patents and other intellectual property protection, especially those relating to novel therapeutic products or techniques, and the requirements for patentability differ, in varying degrees, from country to country, and the laws of some foreign countries do not protect intellectual property rights, including trade secrets, to the same extent as federal and state laws of the United States. As a result, many companies have encountered significant problems in protecting and defending intellectual property rights in certain foreign jurisdictions. Such issues may make it difficult for us to stop the infringement, misappropriation or other violation of our other intellectual property rights. For example, many foreign countries have compulsory licensing laws under which a patent owner must grant licenses to third parties. In addition, many countries limit the enforceability of patents against third parties, including government agencies or government contractors. In these countries, patents may provide limited or no benefit. In those countries, we and our licensors may have limited remedies if patents are infringed or if we or our licensors are compelled to grant a license to a third party, which could materially diminish the value of those patents. This could limit our potential revenue opportunities. Accordingly, our and our licensors’ efforts to enforce intellectual property rights around the world may be inadequate to obtain a significant commercial advantage from the intellectual property that we own or license. Similarly, if our trade secrets are disclosed in a foreign jurisdiction, competitors worldwide could have access to our proprietary information and we may be without satisfactory recourse. Such disclosure could have a material adverse effect on our business. Moreover, our ability to protect and enforce our intellectual property rights may be adversely affected by unforeseen changes in foreign intellectual property laws.

Furthermore, proceedings to enforce our licensors’ and our patent rights and other intellectual property rights in foreign jurisdictions could result in substantial costs and divert our efforts and attention from other aspects of our business, could put our or our licensors’ patents at risk of being invalidated or interpreted narrowly, could put our or our licensors’ patent applications at risk of not issuing and could provoke third parties to assert claims against us or our licensors. We may not prevail in any lawsuits that we initiate and the damages or other remedies awarded to us, if any, may not be commercially meaningful, while the damages and other remedies we may be ordered to pay such third parties may be significant. In addition, changes in the law and legal decisions by courts in the United States and foreign countries may affect our ability to obtain adequate protection for our technology and the enforcement of intellectual property. Accordingly, our licensors’ and our efforts to enforce our intellectual property rights around the world may be inadequate to obtain a significant commercial advantage from the intellectual property that we develop or license.

Third parties may in the future make claims challenging the inventorship or ownership of our or our licensors’ intellectual property. We have written agreements with collaborators that provide for the ownership of intellectual property arising from our collaborations. These agreements provide that we must negotiate certain commercial rights with such collaborators with respect to joint inventions or inventions made by our collaborators that arise from the results of the collaboration. In some instances, there may not be adequate written provisions to address clearly the resolution of intellectual property rights that may arise from a collaboration. If we cannot successfully negotiate sufficient ownership and commercial rights to the inventions that result from our use of a third-party collaborator’s materials where required, or if disputes otherwise arise with respect to the intellectual property developed through a collaboration, we may be limited in our ability to capitalize on the full market potential of these inventions. In addition, we may face claims by third parties that our agreements with employees, contractors or consultants obligating them to assign intellectual property to us are ineffective, or in conflict with prior or competing contractual obligations of assignment, which could result in ownership disputes regarding intellectual property we have developed or will develop and could interfere with our ability to capture the full commercial value of such inventions. Litigation may be necessary to resolve an ownership dispute, and if we are not successful, we may be precluded from using certain intellectual property and associated products, product candidates, processes and technologies, or may lose our rights in that intellectual property. Either outcome could have an adverse impact on our business.

We currently employ, and in the future may employ, individuals who were previously employed at universities or other biotechnology, pharmaceutical or nanomedicine companies, including our competitors or potential competitors. Although we try to ensure that our employees and consultants do not use the proprietary information or know-how of others in their work for us, we may be subject to claims that we or our employees, consultants or independent contractors have inadvertently or otherwise used or disclosed intellectual property, including trade secrets or other proprietary information,

of a former employer or other third parties. Litigation may be necessary to defend against these claims. If we fail in defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights or personnel or damage our reputation. Even if we are successful in defending against such claims, litigation could result in substantial costs and be a distraction to management and other employees.

There is significant litigation in the fields of pharmaceutical and medical device development regarding patent and other intellectual property rights. While we are not currently subject to any pending intellectual property litigation, and are not aware of any such threatened litigation, we may be exposed to future litigation by third parties based on claims that our products, product candidates, processes, technologies or activities infringe the intellectual property rights of others. If our development activities are found to infringe any such patents, we may have to pay significant damages or seek licenses to such patents. A patentee could prevent us from using the patented drugs or compositions. In addition, we may need to resort to litigation to enforce a patent issued to us, to protect our trade secrets, or to determine the scope and validity of third-party proprietary rights. If we initiate or threaten patent infringement litigation, such action could provoke third parties to assert claims against us or our licensors or could put our patents at risk of being invalidated or interpreted narrowly. From time to time, we may hire scientific personnel or consultants formerly employed by other companies involved in one or more areas similar to the activities conducted by us. Either we or these individuals may be subject to allegations of trade secret misappropriation or other similar claims as a result of prior affiliations. If we become involved in litigation, it could consume a substantial portion of our managerial and financial resources, regardless of whether we win or lose. We may not be able to afford the costs of litigation. Any adverse ruling or perception of an adverse ruling in defending ourselves against these claims could have a negative impact on our cash position. Any legal action against us or our collaborators could lead to:

Any of these outcomes could hurt our cash position and financial condition and our ability to develop and commercialize our product candidates.

Our registered or unregistered trademarks or trade names may be challenged, infringed, circumvented or declared generic or determined to be infringing on other marks. We may not be able to protect our rights to these trademarks and trade names or may be forced to stop using these names and trademarks, which we need to build name recognition by potential partners or customers in our markets of interest. If we are unable to establish name recognition based on our trademarks and trade names, we may not be able to compete effectively and our business may be adversely affected.

Prior to the completion of the offering, while our ordinary shares have been traded on Euronext Paris since October 2012, there has been no public market on a U.S. national securities exchange for the ADSs or our ordinary shares in the United States. An active trading market for our ADSs may never develop or be sustained following the U.S. offering. If an active trading market does not develop, you may have difficulty selling your ADSs at an attractive price, or at all. The price for our ADSs in the U.S. offering will be determined by negotiations among us and representatives of the underwriters, and it may not be indicative of prices that will prevail in the open market after the offering. Consequently, you may not be able to sell your ADSs at or above the initial public offering price or at any other price or at the time that you would like to sell. An inactive market may also impair our ability to raise capital by selling our ADSs, and it may

impair our ability to attract and motivate our employees through equity incentive awards and our ability to acquire other companies, products or technologies by using our ADSs as consideration.

You should consider an investment in our ordinary shares or ADSs to be risky, and you should invest in our ordinary shares or ADSs only if you can withstand a significant loss and wide fluctuations in the market value of your investment. Some factors that may cause the market price of our ordinary shares or ADSs to fluctuate, in addition to the other risks mentioned in this section of the prospectus, are:

These and other market and industry factors may cause the market price and demand for our ordinary shares and ADSs to fluctuate substantially, regardless of our actual operating performance, which may limit or prevent investors from readily selling their ordinary shares or ADSs and may otherwise negatively affect the liquidity of the trading market for the ordinary shares and ADSs. In addition, the stock market in general, and pharmaceutical, biotechnology and nanomedicine companies in particular, have experienced extreme price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of these companies.

Our management will have broad discretion to use the net proceeds we receive from the offering and you will be relying on its judgment regarding the application of these proceeds. We may spend or invest these proceeds in a way with which our shareholders disagree. The failure by our management to apply these funds effectively could harm our business and

financial condition. We expect to use the net proceeds from the offering as described under the heading “Use of Proceeds.” However, management may not apply the net proceeds of the offering in ways that increase the value of your investment.

We have never declared or paid any cash dividends on our ordinary shares and do not currently intend to do so for the foreseeable future. We currently intend to invest our future earnings, if any, to fund our growth. Therefore, you are not likely to receive any dividends on your ordinary shares or ADSs for the foreseeable future, and the success of an investment in ordinary shares or ADSs will depend upon any future appreciation in its value. Consequently, investors may need to sell all or part of their holdings of ordinary shares or ADSs after price appreciation, which may never occur, as the only way to realize any future gains on their investment. There is no guarantee that the ordinary shares or ADSs will appreciate in value or even maintain the price at which our shareholders have purchased them. Investors seeking cash dividends should not purchase the ADSs or ordinary shares.

Further, under French law, the determination of whether we have been sufficiently profitable to pay dividends is made on the basis of our statutory financial statements prepared and presented in accordance with accounting standards applicable in France. In addition, payment of dividends may subject us to additional taxes under French law. See “Description of Share Capital—Key Provisions of Our By-laws and French Law Affecting Our Ordinary Shares—Rights, Preferences and Restrictions Attaching to Ordinary Shares” for further details on the limitations on our ability to declare and pay dividends. Therefore, we may be more restricted in our ability to declare dividends than companies not based in France.

In addition, exchange rate fluctuations may affect the amount of euros that we are able to distribute, and the amount in U.S. dollars that our shareholders receive upon the payment of cash dividends or other distributions we declare and pay in euros, if any. These factors could harm the value of the ADSs, and, in turn, the U.S. dollar proceeds that holders receive from the sale of the ADSs.

If you purchase ordinary shares or ADSs in the offering, you will experience substantial and immediate dilution of $9.64 per ADS and €11.67 per ordinary share in pro forma net tangible book value after giving effect to the offering at an assumed public offering price of $14.00 per ADS in the U.S. offering which corresponds to €11.56 per ordinary share in the European offering which is the midpoint of the price range set forth on the cover page of this prospectus, because the price that you pay will be substantially greater than the pro forma net tangible book value per ADS or ordinary share, as applicable, that you acquire. For a further description of the dilution that you will experience immediately after the offering, see “Dilution.”

If our existing shareholders sell, or indicate an intent to sell, substantial amounts of ordinary shares or ADSs in the public market after any applicable contractual or legal restrictions on resale discussed in this prospectus lapse, the trading price of the ADSs and ordinary shares could decline significantly and could decline below the offering price. Upon completion of the offering, we will have outstanding 32,537,122 ordinary shares (including ordinary shares in the form of ADSs) assuming no issuance by us of additional ordinary shares (including in the form of ADSs) pursuant to the exercise in full of the underwriters’ option, approximately 33,512,122 of which are subject to a contractual restriction on selling for up to 90 days, subject to customary exceptions. The underwriters may permit our executive board members and supervisory board members to sell ADSs or ordinary shares prior to the expiration of the lock-up agreements. See “Underwriting.”

After the 90-day lock-up agreements with executive and supervisory board members expire, and based on the number of ordinary shares outstanding upon completion of the offering (including ordinary shares in the form of ADSs), 949,863 additional ordinary shares will be eligible for sale in the public market, all of which shares are held by supervisory board members and executive board members and will be subject to volume limitations under Rule 144 under the Securities Act. In addition, the ordinary shares subject to outstanding warrants or stock options and outstanding free shares will become eligible for sale in the public market in the future, subject to certain legal and contractual limitations. Following

the offering and expiration of the lock-up period, we intend to file one or more registration statements with the SEC covering the ordinary shares issuable upon exercise of outstanding warrants or stock options and outstanding free shares. Upon effectiveness of such registration statements, any ordinary shares subsequently issued will be eligible for sale in the public market, except to the extent that they are restricted by the lock-up agreements referred to above and subject to compliance with Rule 144 in the case of our affiliates. Sales of a large number of the shares in the public market could have an adverse effect on the market price of the ADSs or ordinary shares. See “Shares and ADSs Eligible for Future Sale” for a more detailed description of sales that may occur in the future. If these additional ordinary shares are sold, or if it is perceived that they will be sold, in the public market, the trading price of the ADSs and ordinary shares could decline substantially.

Holders of ADSs may exercise voting rights with respect to the ordinary shares represented by the ADSs only in accordance with the provisions of the deposit agreement and not as a direct shareholder. The deposit agreement provides that, upon receipt of notice of any meeting of holders of our ordinary shares, the depositary will fix a record date for the determination of ADS holders who shall be entitled to give instructions for the exercise of voting rights. Upon timely receipt of notice from us, if we so request, the depositary shall distribute to the holders as of the record date (1) the notice of the meeting or solicitation of consent or proxy sent by us and (2) a statement as to the manner in which instructions may be given by the holders.

Purchasers of ADSs in the U.S. offering may instruct the depositary of their ADSs to vote the ordinary shares underlying their ADSs. Otherwise, purchasers of ADSs in the U.S. offering will not be able to exercise voting rights, unless they withdraw the ordinary shares underlying the ADSs they hold. However, a holder of ADSs may not know about the meeting far enough in advance to withdraw those ordinary shares. If we ask for a holder of ADSs’ instructions, the depositary, upon timely notice from us, will notify him or her of the upcoming vote and arrange to deliver our voting materials to him or her. We cannot guarantee to any holder of ADSs that he or she will receive the voting materials in time to ensure that he or she can instruct the depositary to vote his or her ordinary shares or to withdraw his or her ordinary shares so that he or she can vote them. If the depositary does not receive timely voting instructions from a holder of ADSs, it may give a proxy to a person designated by us to vote the ordinary shares underlying his or her ADSs. In addition, the depositary and its agents are not responsible for failing to carry out voting instructions or for the manner of carrying out voting instructions. This means that a holder of ADSs may not be able to exercise his or her right to vote, and there may be nothing he or she can do if the ordinary shares underlying his or her ADSs are not voted as he or she requested.

A holder of ADSs will not be treated as one of our shareholders and will not have direct shareholder rights. French law governs our shareholder rights. The depositary, through the custodian or the custodian’s nominee, will be the holder of the ordinary shares underlying ADSs held by purchasers of ADSs in the U.S. offering. Purchasers of ADSs in the U.S. offering will have ADS holder rights. Among other things, ADS holder rights do not provide for double voting rights, which otherwise would be available to holders of ordinary shares held in a shareholders' name for a period of at least two years. The deposit agreement among us, the depositary and purchasers of ADSs in the U.S. offering, as an ADS holder, and all other persons directly and indirectly holding ADSs, sets out ADS holder rights, as well as the rights and obligations of us and the depositary.

According to French law, if we issue additional securities for cash, current shareholders will have preferential subscription rights for these securities on a pro rata basis unless they waive those rights at an extraordinary meeting of our shareholders (by a two-thirds majority vote) or individually by each shareholder. However, our ADS holders in the United States will not be entitled to exercise or sell such rights unless we register the rights and the securities to which the rights relate under the Securities Act or an exemption from the registration requirements is available. In addition, the deposit agreement provides that the depositary will not make rights available to purchasers of ADSs in the U.S. offering unless the distribution to ADS holders of both the rights and any related securities are either registered under the Securities Act or exempted from registration under the Securities Act. Further, if we offer holders of our ordinary shares the option to receive dividends in either cash or shares, under the deposit agreement the depositary may require satisfactory assurances from us that extending the offer to holders of ADSs does not require registration of any securities under the Securities Act before making the option available to holders of ADSs. We are under no obligation to file a registration statement with respect to any such rights or securities or to endeavor to cause such a registration statement

to be declared effective. Moreover, we may not be able to establish an exemption from registration under the Securities Act. Accordingly, ADS holders may be unable to participate in our rights offerings or to elect to receive dividends in shares and may experience dilution in their holdings. In addition, if the depositary is unable to sell rights that are not exercised or not distributed or if the sale is not lawful or reasonably practicable, it will allow the rights to lapse, in which case you will receive no value for these rights.

ADSs, which may be evidenced by American Depositary Receipts (“ADRs”), are transferable on the books of the depositary. However, the depositary may close its books at any time or from time to time when it deems expedient in connection with the performance of its duties. The depositary may refuse to deliver, transfer or register transfers of ADSs generally when our books or the books of the depositary are closed, or at any time if we or the depositary think it is advisable to do so because of any requirement of law, government or governmental body, or under any provision of the deposit agreement, or for any other reason subject to a holder of ADSs’ right to cancel his or her ADSs and withdraw the underlying ordinary shares. Temporary delays in the cancellation of ADSs and withdrawal of the underlying ordinary shares may arise because the depositary has closed its transfer books or we have closed our transfer books, the transfer of ordinary shares is blocked to permit voting at a shareholders’ meeting or we are paying a dividend on our ordinary shares. In addition, a holder of ADSs may not be able to cancel his or her ADSs and withdraw the underlying ordinary shares when he or she owes money for fees, taxes and similar charges and when it is necessary to prohibit withdrawals in order to comply with any laws or governmental regulations that apply to ADSs or to the withdrawal of ordinary shares or other deposited securities. See “Description of American Depositary Shares.”

We are an “emerging growth company,” as defined in the JOBS Act. As an emerging growth company, we intend to take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not “emerging growth companies,” including, but not limited to, not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act, and exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and shareholder approval of any golden parachute payments not previously approved.

We cannot predict if investors will find the ADSs less attractive because we rely on these exemptions. If some investors find the ADSs less attractive as a result, there may be a less active trading market for the ADSs and the price of the ADSs may be more volatile. We intend to take advantage of these reporting exemptions until we are no longer an emerging growth company. We will remain an emerging growth company until the earliest of (i) the last day of the fiscal year in which we have total annual gross revenue of $1.07 billion or more; (ii) the last day of our fiscal year following the fifth anniversary of the date of the completion of the offering; (iii) the date on which we have issued more than $1.0 billion in nonconvertible debt during the previous three years; and (iv) the date on which we are deemed to be a large accelerated filer under the rules of the SEC. Once we cease to be an emerging growth company, we may continue to avail ourselves of the accommodations available to us as a foreign private issuer for so long as we qualify as such.

The deposit agreement governing the ADSs representing our ordinary shares provides that, to the fullest extent permitted by law, ADS holders, including holders who acquire ADSs in the secondary market, waive the right to a jury trial of any claim they may have against us or the depositary arising out of or relating to our shares, the ADSs or the deposit agreement, including any claim under the U.S. federal securities laws.

If we or the depositary opposed a jury trial demand based on the waiver, the court would determine whether the waiver was enforceable based on the facts and circumstances of that case in accordance with the applicable state and federal law. To our knowledge, the enforceability of a contractual pre-dispute jury trial waiver in connection with claims arising under the federal securities laws has not been finally adjudicated by the United States Supreme Court. However, we believe that a contractual pre-dispute jury trial waiver provision is generally enforceable, including under the laws of the State of New York, which govern the deposit agreement, by a federal or state court in the City of New York, which has non-exclusive jurisdiction over matters arising under the deposit agreement. In determining whether to enforce a contractual pre-dispute jury trial waiver provision, courts will generally consider whether a party knowingly, intelligently

and voluntarily waived the right to a jury trial. We believe that this is the case with respect to the deposit agreement and the ADSs. It is advisable that you consult legal counsel regarding the jury waiver provision before entering into the deposit agreement.

If you or any other holders or beneficial owners of ADSs bring a claim against us or the depositary in connection with matters arising under the deposit agreement or the ADSs, including claims under federal securities laws, you or such other holder or beneficial owner may not be entitled to a jury trial with respect to such claims, which may have the effect of limiting and discouraging lawsuits against us and the depositary. If a lawsuit is brought against either or both of us and the depositary under the deposit agreement, it may be heard only by a judge or justice of the applicable trial court, which would be conducted according to different civil procedures and may result in different outcomes than a trial by jury would have, including results that could be less favorable to the plaintiffs in any such action.

Nevertheless, if this jury trial waiver provision is not permitted by applicable law, an action could proceed under the terms of the deposit agreement with a jury trial. No condition, stipulation or provision of the deposit agreement or ADSs serves as a waiver by any holder or beneficial owner of ADSs or by us or the depositary of compliance with U.S. federal securities laws and the rules and regulations promulgated thereunder.

We are a French company with limited liability. Our corporate affairs are governed by our By-laws and by the laws governing companies incorporated in France. The rights of shareholders and the responsibilities of members of our executive board and supervisory board are in many ways different from the rights and obligations of shareholders in companies governed by the laws of U.S. jurisdictions. For example, in the performance of its duties, our executive board and supervisory board are required by French law to consider the interests of our company, its shareholders, its employees and other stakeholders, rather than solely our shareholders and/or creditors. It is possible that some of these parties will have interests that are different from, or in addition to, your interests as a shareholder or holder of ADSs. Further, in accordance with French law, double voting rights automatically attach to each ordinary share of companies listed on a regulated market (such as Euronext Paris, where our ordinary shares are listed) that is held of record in the name of the same shareholder for a period of at least two years, except as otherwise set forth in a company’s by-laws. Our By-laws currently do not exclude such double voting rights. See “Management—Corporate Governance Practices” and “Description of Share Capital.” Ordinary shares held in the form of ADSs will not be eligible for double voting rights.

Certain members of our executive board, supervisory board and senior management and certain experts named in this prospectus are non-residents of the United States, and all or a substantial portion of our assets and the assets of such persons are located outside the United States. As a result, it may not be possible to serve process on such persons or us in the United States or to enforce judgments obtained in U.S. courts against them or us based on civil liability provisions of the securities laws of the United States. Additionally, it may be difficult to assert U.S. securities law claims in actions originally instituted outside of the United States. Foreign courts may refuse to hear a U.S. securities law claim because foreign courts may not be the most appropriate forums in which to bring such a claim. Even if a foreign court agrees to hear a claim, it may determine that the law of the jurisdiction in which the foreign court resides, and not U.S. law, is applicable to the claim. Further, if U.S. law is found to be applicable, the content of applicable U.S. law must be proved as a fact, which can be a time-consuming and costly process, and certain matters of procedure would still be governed by the law of the jurisdiction in which the foreign court resides. In particular, there is some doubt as to whether French courts would recognize and enforce certain civil liabilities under U.S. securities laws in original actions or judgments of U.S. courts based upon these civil liability provisions. In addition, awards of punitive damages in actions brought in the United States or elsewhere may be unenforceable in France. An award for monetary damages under the U.S. securities laws would be considered punitive if it does not seek to compensate the claimant for loss or damage suffered but is intended to punish the defendant. French law provides that a shareholder, or a group of shareholders, may initiate a legal action to seek indemnification from the directors of a corporation in the corporation’s interest if it fails to bring such legal action itself. If so, any damages awarded by the court are paid to the corporation and any legal fees relating to such action may be borne by the relevant shareholder or the group of shareholders.

The enforceability of any judgment in France will depend on the particular facts of the case as well as the laws and treaties in effect at the time. The United States and France do not currently have a treaty providing for recognition and enforcement of judgments (other than arbitration awards) in civil and commercial matters. See “Enforcement of Civil Liabilities.”

Provisions contained in our By-laws and French corporate law could make it more difficult for a third party to acquire us, even if doing so might be beneficial to our shareholders. In addition, provisions of French law and our By-laws impose various procedural and other requirements, which could make it more difficult for shareholders to effect certain corporate actions. These provisions include the following:

We incur some of our expenses, and may in the future derive revenues, in currencies other than the euro. In particular, as we expand our operations and continue to conduct clinical trials in the United States, we will continue to incur expenses in U.S. dollars. As a result, we may be exposed to foreign currency exchange risk as our results of operations and cash flows would be subject to fluctuations in foreign currency exchange rates. We currently do not engage in hedging transactions to protect against uncertainty in future exchange rates between particular foreign currencies and the euro. Therefore, for example, an increase in the value of the euro against the U.S. dollar could have a negative impact on our revenue and earnings growth as U.S. dollar revenue and earnings, if any, are translated into euros at a reduced value. We cannot predict the impact of foreign currency fluctuations, and foreign currency fluctuations in the future may adversely affect our financial condition, results of operations and cash flows. The ADSs being sold in the U.S. offering will be quoted in U.S. dollars on the Nasdaq Global Select Market, while our ordinary shares trade in euros on the Euronext Paris exchange. Our financial statements are prepared in euros. Therefore, fluctuations in the exchange rate between the euro and the U.S. dollar will also affect, among other matters, the value of our ordinary shares and ADSs.

We operate in a number of jurisdictions and intend to continue to expand our global presence. To date, we have focused our development and planned commercialization efforts on the EU and the United States, and to a lesser extent, Asia. International operations are subject to the legal, political, regulatory, and social requirements and economic conditions in the jurisdictions in which they are conducted. Risks inherent to international operations include, but are not limited to:

We believe that our overall success as a global business depends on our ability to succeed in different legal, regulatory, economic, social, and political situations and conditions. We may not be able to develop and implement effective policies and strategies in each jurisdiction where we may conduct operations or do business in the future.

Our auditor, Ernst & Young et Autres, is registered with the Public Company Accounting Oversight Board (PCAOB) in the United States. The PCAOB’s cooperative arrangement with the French audit authority expired in December 2019. This expiration of this cooperative arrangement prevents inspections of registered firms in France until a new arrangement is concluded. Such inspections assess a registered firm’s compliance with U.S. law and professional standards in connection with the performance of audits of financial statements filed with the SEC. As a result, our investors may not realize the potential benefits of such inspections until a new cooperative arrangement, which is currently under negotiation, is entered into and inspections in France resume.

We are a foreign private issuer, as defined in the SEC’s rules and regulations and, consequently, we are not subject to all of the disclosure requirements applicable to public companies organized within the United States. For example, we are exempt from certain rules under the Exchange Act that regulate disclosure obligations and procedural requirements related to the solicitation of proxies, consents or authorizations applicable to a security registered under the Exchange Act, including the U.S. proxy rules under Section 14 of the Exchange Act. In addition, our executive board members and supervisory board members are exempt from the reporting and “short-swing” profit recovery provisions of Section 16 of the Exchange Act and related rules with respect to their purchases and sales of our securities. Moreover, while we currently make annual and semi-annual filings with respect to our listing on Euronext Paris and expect to file financial reports on an annual basis with the SEC and furnish semi-annual financial information with the SEC, we will not be required to file periodic reports and financial statements with the SEC as frequently or as promptly as U.S. public companies and will not be required to file quarterly reports on Form 10-Q or current report on Form 8-K under the Exchange Act. Accordingly, there will be less publicly available information concerning our company than there would be if we were not a foreign private issuer.

As a foreign private issuer listed on the Nasdaq Global Select Market, we will be subject to Nasdaq’s corporate governance standards. However, Nasdaq rules provide that foreign private issuers are permitted to follow home country corporate governance practices in lieu of Nasdaq’s corporate governance standards as long as notification is provided to Nasdaq of the intention to take advantage of such exemptions. Certain corporate governance practices in France, which is our home country, may differ significantly from Nasdaq corporate governance standards. Other than as set forth in the section of this prospectus titled “Management—Corporate Governance Practices,” we currently intend to comply with the corporate governance listing standards of Nasdaq to the extent possible under French law. However, we may choose to change such practices to follow additional French home country practices in the future.

As a result of the accommodations for foreign private issuers, our shareholders may be afforded less protection than they otherwise would have under Nasdaq’s corporate governance standards applicable to U.S. domestic issuers. For an overview of our corporate governance practices, see “Management—Corporate Governance Practices.”

While we currently qualify as a foreign private issuer, the determination of foreign private issuer status is made annually on the last business day of an issuer’s most recently completed second fiscal quarter and, accordingly, the next determination will be made with respect to us on June 30, 2021. In the future, we would lose our foreign private issuer status if we fail to meet the requirements necessary to maintain our foreign private issuer status as of the relevant determination date. For example, if more than 50% of our securities are held by U.S. residents and more than 50% of our executive board members or supervisory board members are residents or citizens of the United States, we could lose our foreign private issuer status. Immediately following the closing of the offering, approximately 25% of our outstanding ordinary shares will likely be held by U.S. residents (assuming that all purchasers in the U.S. offering are residents of the United States).

The regulatory and compliance costs to us under U.S. securities laws as a U.S. domestic issuer may be significantly more than costs we incur as a foreign private issuer. If we are not a foreign private issuer, we will be required to file periodic reports and registration statements on U.S. domestic issuer forms with the SEC, which are more detailed and extensive in certain respects than the forms available to a foreign private issuer. We would be required under current SEC rules to prepare our financial statements in accordance with U.S. GAAP, rather than IFRS, and modify certain of our policies to comply with corporate governance practices associated with U.S. domestic issuers. Such conversion of our financial statements to U.S. GAAP would involve significant time and cost. In addition, we may lose our ability to rely upon exemptions from certain corporate governance requirements on U.S. stock exchanges that are available to foreign private issuers such as the ones described under “Management—Corporate Governance Practices” and exemptions from procedural requirements related to the solicitation of proxies.

A non-U.S. corporation will be considered a PFIC for any taxable year if either (1) at least 75% of its gross income for such year is passive income or (2) at least 50% of the value of its assets (based on an average of the quarterly values of the assets during such year) is attributable to assets that produce or are held for the production of passive income. Passive income for this purpose generally includes, among other things, dividends, interest, rents, royalties, gains from commodities and securities transactions, and gains from assets that produce passive income. In determining whether a foreign corporation is a PFIC, a pro rata portion of the income and assets of each corporation in which it owns, directly or indirectly, at least a 25% interest (by value) is taken into account. Although not free from doubt, we do not believe that we were a PFIC for the taxable year ended December 31, 2019. However, it is not yet known whether we will be a PFIC in subsequent taxable years. The determination of PFIC status is fact-specific, and a separate determination must be made each taxable year as to whether we are a PFIC (after the close of each such taxable year). Our status as a PFIC depends on the composition of our income (including whether reimbursements of certain refundable research tax credits will constitute gross income for purposes of the PFIC income test) and the composition and value of our assets. The value of our assets may be determined in large part by reference to the market value of the ADSs and our ordinary shares, which may fluctuate substantially. Our status as a PFIC may also depend in part upon how quickly we utilize the cash proceeds from the offering (and the cash proceeds from other fund-raising activities) in our business.

If we are a PFIC for any taxable year during which a U.S. holder holds ADSs, the U.S. holder may be subject to adverse tax consequences, including (1) the treatment of all or a portion of any gain on disposition as ordinary income, (2) the application of an interest charge with respect to such gain and certain dividends and (3) compliance with certain reporting requirements. Each U.S. holder is strongly urged to consult its tax advisor regarding these issues and any available elections to mitigate such tax consequences. See “Taxation—Material U.S. Federal Income Tax Considerations.”

Pursuant to the provisions of the French Monetary and Financial Code (code monétaire et financier), any investment by any non-French citizen, any French citizen not residing in France, any non-French entity or any French entity controlled by one of the aforementioned persons or entities that will result in the relevant investor (a) acquiring control of an entity registered in France, (b) acquiring all or part of a business line of an entity registered in France, or (c) for non-EU or non-EEA investors crossing, directly or indirectly, alone or in concert, a 25% threshold of voting rights in an entity

registered in France, in each case, conducting activities in certain strategic industries, such as the industry in which we operate, is subject to the prior authorization of the French Ministry of Economy, which authorization may be conditioned on certain undertakings.

In the context of the ongoing COVID-19 pandemic, the Decree (décret) n°2020 892 dated July 22, 2020 has created until December 31, 2020 a new 10% threshold of the voting rights for the non-European investments in listed companies, in addition to the 25% above-mentioned threshold.

The foreign investment control regime described above applies to companies engaged in activities essential to protecting public health as well as biotechnology-related research and development activities.

On November 5, 2020, the French Ministry of Economy informed us that our activities are subject to the above described foreign investment control regime. Therefore, any investor meeting the above criteria willing to acquire all or part of our business with the effect of crossing the applicable share capital thresholds set forth by the French Monetary and Financial Code will have to request this prior governmental authorization before acquiring our ordinary shares or ADSs. We cannot guarantee that such investor will obtain the necessary authorization in due time. The authorization may also be granted subject to conditions that deter a potential purchaser. The existence of such conditions to an investment in our securities could have a negative impact on our ability to raise the funds necessary to our development. In addition, failure to comply with such measures could result in significant consequences for the investor (including the investment to be deemed null and void). Such measures could also delay or discourage a takeover attempt, and we cannot predict whether these measures will result in a lower or more volatile market price of our ADSs or ordinary shares.

For more details on the French foreign investment control regime see “Limitations Affecting Shareholders of a French Company - Ownership of ADSs or Shares by Non-French Residents”

We must maintain effective internal control over financial reporting in order to accurately and timely report our results of operations and financial condition. In addition, as a public company listed in the United States, the Sarbanes-Oxley Act will require, among other things, that we assess the effectiveness of our internal control over financial reporting at the end of each fiscal year. We anticipate being first required to issue management’s annual report on internal control over financial reporting, pursuant to Section 404 of the Sarbanes-Oxley Act, in connection with issuing our consolidated financial statements as of and for the year ending December 31, 2021 and the filing of our second annual report with the SEC, which would be required on or before April 30, 2022.

The rules governing the standards that must be met for our management to assess our internal control over financial reporting pursuant to Section 404 of the Sarbanes-Oxley Act are complex and require significant documentation, testing and possible remediation. These stringent standards require that our audit committee be advised and regularly updated on management’s review of internal control over financial reporting. We are in the process of designing, implementing, and testing the internal control over financial reporting required to comply with this obligation. This process is time-consuming, costly, and complicated. In addition, our independent registered public accounting firm will be required to attest to the effectiveness of our internal controls over financial reporting beginning with our annual report following the date on which we are no longer an emerging growth company, which may be up to five fiscal years following the date of the offering. Our management may not be able to effectively and timely implement controls and procedures that adequately respond to the increased regulatory compliance and reporting requirements that will be applicable to us as a public company listed in the United States. If we fail to staff our accounting and finance function adequately or maintain internal control over financial reporting adequate to meet the demands that will be placed upon us as a public company listed in the United States, our business and reputation may be harmed and the price of our ordinary shares and ADSs may decline. Furthermore, investor perceptions of us may be adversely affected, which could cause a decline in the market price of our securities.

Despite the implementation of security measures, our internal computer systems, and those of third parties on which we rely, are vulnerable to damage from computer viruses, malware, unauthorized access, natural disasters, terrorism, war, telecommunication and electrical failures, cyber-attacks or cyber-intrusions over the Internet, attachments to emails, persons inside our organization, or persons with access to systems inside our organization. If such an event were to occur and cause interruptions in our systems, it could result in a material disruption of our operations. For example, the loss of clinical trial data for our product candidates could result in delays in our regulatory approval, certification and commercialization efforts and significantly increase our costs to recover or reproduce the lost data. In addition, system redundancy may be ineffective or inadequate, and our disaster recovery planning may not be sufficient to cover all eventualities. To the extent that any disruption or security breach results in a loss of or damage to our data or applications or other data or applications relating to our technology or product candidates, or inappropriate disclosure of confidential or proprietary information, we could incur liabilities, damage to our reputation, and the further development of our product candidates could be delayed. In addition, we may not have adequate insurance coverage to compensate for any losses associated with such events.

There has been a marked increase in the use of social media platforms and similar devices, including weblogs (blogs), social media websites and other forms of Internet-based communications which allow individual access to a broad audience of interested persons. The medical community and care prescribers may value any such readily available information concerning our products or product candidates and may act on such information without further investigation, authentication and without regard to its accuracy. Social media platforms and devices immediately publish the content their subscribers and participants post, often without filters or checks on accuracy of the content posted. The opportunity for dissemination of information, including inaccurate information, is virtually limitless. Information concerning or affecting us, including information regarding our products, product candidates or proprietary nanotechnology, may be posted by third parties on such platforms and devices at any time. Information posted may be inaccurate and adverse to us, and it may harm our business or reputation. The harm may be immediate without affording us an opportunity for redress or correction. Further, such inaccurate information may require us to engage in a defensive media campaign, which may divert our management’s attention or result in an increase in our expenses. Such platforms also could be used for the dissemination of trade secret information or compromise of other valuable company assets, any of which could harm our business.

We may decide to acquire companies or technologies facilitating access to, or enabling us to access, new therapeutic solutions, new research projects, or new geographical areas, or enabling us to express synergies with our existing operations. If such acquisitions were to become necessary or attractive in the future, we may not be able to identify appropriate targets or make acquisitions under satisfactory conditions, in particular, satisfactory price conditions. In addition, we may be unable to obtain the financing for these acquisitions on favorable terms, which could require us to finance these acquisitions using our existing cash resources that could have been allocated to other purposes, including existing business activities. If we acquire businesses with promising markets or technologies, we may not be able to realize the benefit of acquiring such businesses if we are unable to successfully integrate them with our existing operations and company culture. We may encounter numerous difficulties in developing, manufacturing and marketing any new products resulting from a strategic alliance or acquisition that delay or prevent us from realizing their expected benefits or enhancing our business. We cannot assure you that, following any such acquisition, we will achieve the expected synergies to justify the transaction.

On December 22, 2017, U.S. tax reform legislation known as the Tax Cuts and Jobs Act was signed into law. The Tax Cuts and Jobs Act makes substantial changes to U.S. tax law, including a reduction in the corporate income tax rate, a limitation on the use of new operating losses to offset future taxable income, the modification or repeal of certain business deductions and credits, and new rules designed to prevent erosion of the U.S. income tax base such as a new minimum tax, called the Base Erosion and Anti-abuse Tax, applicable to certain U.S. corporations that make certain payments to related foreign persons. The extent of the impact of the Tax Cuts and Jobs Act on our U.S. subsidiary remains uncertain at this time and is subject to other regulatory or administrative developments, including any regulations or other guidance promulgated by the U.S. Internal Revenue Service (the “IRS”).

The trading market for the ADSs and ordinary shares depends in part on the research and reports that securities or industry analysts publish about us or our business. If no or few securities or industry analysts cover our company, the trading price for the ADSs and ordinary shares would be negatively impacted. If one or more of the analysts who covers us downgrades our equity securities or publishes incorrect or unfavorable research about our business, the price of the ordinary shares and ADSs would likely decline. If one or more of these analysts ceases coverage of our company or fails to publish reports on us regularly, or downgrades our securities, demand for the ordinary shares and ADSs could decrease, which could cause the price of the ordinary shares and ADSs or their trading volume to decline.

This prospectus, particularly the sections of this prospectus titled “Summary,” “Risk Factors,” “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and “Business,” contains forward-looking statements. All statements other than present and historical facts and conditions contained in this prospectus, including statements regarding our future results of operations and financial position, business strategy, plans and our objectives for future operations, are forward-looking statements. When used in this prospectus, the words “anticipate,” “believe,” “can,” “could,” “estimate,” “expect,” “intend,” “is designed to,” “may,” “might,” “plan,” “potential,” “predict,” “objective,” “shall,” “should,” “will,” or the negative of these and similar expressions identify forward-looking statements. Such statements are subject to risks and uncertainties, and actual results may differ materially from those expressed or implied in the forward-looking statements due to various factors, including, but not limited to, those identified under the section entitled “Risk Factors” in this prospectus. These risks and uncertainties include factors relating to:

As a result of these factors, we cannot assure you that the forward-looking statements in this prospectus will prove to be accurate. Furthermore, if our forward-looking statements prove to be inaccurate, the inaccuracy may be material. In light of the significant uncertainties in these forward-looking statements, you should not regard these statements as a representation or warranty by us or any other person that we will achieve our objectives and plans in any specified time frame or at all. We undertake no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law. In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements. The Private Securities Litigation Reform Act of 1995 and Section 27A of the Securities Act do not protect any forward-looking statements that we make in connection with this offering.

You should read this prospectus and the documents that we reference in this prospectus and have filed as exhibits to the registration statement, of which this prospectus is a part, completely and with the understanding that our actual future results may be materially different from what we expect. We qualify all of our forward-looking statements by these cautionary statements.

We estimate that we will receive net proceeds from the offering of approximately €65.8 ($79.6) million, assuming an offering price of $14.00 per ADS in the U.S. offering and €11.56 per ordinary share in the European offering which is the midpoint of the price range set forth on the cover page of this prospectus, after deducting estimated underwriting commissions and estimated offering expenses payable by us, and assuming no issuance by us of additional ordinary shares (which may be in the form of ADSs) pursuant to the exercise of the underwriters’ option to purchase up to 975,000 additional ordinary shares in this offering (which may be in the form of ADSs). If we issue additional ordinary shares (including in the form of ADSs) pursuant to the exercise in full of the underwriters’ option in the offering, we estimate that we will receive net proceeds from the offering of approximately €76.2 ($92.3) million, based on the same assumptions stated above.

Each €1.00 ($1.2109) increase (decrease) in the assumed offering price of $14.00 per ADS (€11.56 per ordinary share) would increase or decrease our net proceeds from the offering by €6.0 ($7.3) million, assuming the number of ordinary shares offered by us (which may be in the form of ADSs), as set forth on the cover page of this prospectus, remains the same and after deducting estimated underwriting commissions and estimated offering expenses payable by us. We may also increase or decrease the number of ordinary shares (which may be in the form of ADSs) we are offering. An increase or decrease of 1,000,000 ordinary shares (including those in the form of ADSs) offered by us would increase or decrease the net proceeds to us from the sale of the ordinary shares we are offering by €10.8 ($13.0) million, assuming that the assumed offering price remains the same and after deducting estimated underwriting commissions and estimated offering expenses payable by us. The actual net proceeds payable to us will adjust based on the actual number of ordinary shares (including in the form of ADSs) offered by us in the offering, the actual offering price and other terms of the offering determined at pricing.

We currently expect to use the net proceeds from the offering to advance the overall development of NBTXR3, prioritizing the treatment of locally advanced head and neck cancers, including:

We expect to use the remainder of the net proceeds, if any, from the offering for working capital funding and other general corporate purposes.

We expect that the net proceeds from the offering, together with our cash and cash equivalents of €42.4 million as of September 30, 2020, will be sufficient to fund our operating expenses and capital expenditure requirements through the end of 2022. Even with the expected net proceeds from the offering, we may need to raise additional capital in the future. We have based these estimates on assumptions that may prove to be incorrect, and we could use our available capital resources sooner than we currently expect.

This expected use of the net proceeds from the offering represents our intentions based upon our current plans and business conditions. As of the date of this prospectus, we cannot predict with certainty all of the particular uses for the net proceeds to be received upon the completion of the offering or the amounts that we will actually spend on the uses set forth above. The amounts and timing of our actual expenditures and the extent of clinical development may vary significantly depending on numerous factors, including the progress of our development efforts, the status of and results from preclinical studies and any ongoing clinical trials or clinical trials we may commence in the future, as well as any collaborations that we may enter into with third parties for our product candidates and any unforeseen cash needs. As a result, our management will retain broad discretion over the allocation of the net proceeds from the offering.

Pending our use of the net proceeds from the offering, we intend to invest the net proceeds in a variety of capital preservation investments, including short-term, investment-grade, interest-bearing instruments.

We have never declared or paid any cash dividends on our ordinary shares. We do not anticipate paying cash dividends on our equity securities in the foreseeable future and intend to retain all available funds and any future earnings for use in the operation and expansion of our business.

Subject to the requirements of French law and our By-laws, dividends may only be distributed from our distributable profits, plus any amounts held in our available reserves, which are our reserves other than the legal and statutory reserves and the revaluation surplus. The section of this prospectus titled “Description of Share Capital—Key Provisions of Our By-laws and French Law Affecting Our Ordinary Shares—Rights, Preferences and Restrictions Attaching to Ordinary Shares” provides further details on the limitations on our ability to declare and pay dividends. Dividend distributions, if any, will be made in euros and converted into U.S. dollars with respect to the ADSs, as provided in the deposit agreement.

The following table sets forth our cash and cash equivalents and capitalization as of June 30, 2020 on:

Our capitalization following the offering will be adjusted based on the actual offering price and other terms of the offering that will be determined at pricing, including the amount by which actual offering expenses are higher or lower than estimated.

You should read this table together with our financial statements and the related notes thereto beginning on page F-1, as well as the section of this prospectus titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and the other financial information included elsewhere in this prospectus.

The number of ordinary shares (including in the form of ADSs) that will be outstanding after the offering is based on 22,731,122 actual ordinary shares outstanding as of June 30, 2020, before giving effect to the pro forma items described herein, and excludes: 

As of September 30, 2020, there were 26,037,122 ordinary shares outstanding, which reflects the 6,000 ordinary shares granted as free shares prior to June 30, 2020, which vested and were issued on July 27, 2020, and the 3,300,000 ordinary shares issued in the July 2020 Private Placement.

If you invest in our ADSs or ordinary shares in the offering, your ownership interest will be diluted to the extent of the difference between the offering price per ADS or ordinary share paid by you and the pro forma as adjusted net tangible book value per ADS or ordinary share after completion of the offering. Our net tangible book value (deficit) as of June 30, 2020 was €(22.27) million ($(25.02) million), or €(0.98) per ordinary share (equivalent to $(1.10) per ADS, based on an exchange rate of €1.00 = $1.1237). Net tangible book value per ordinary share is determined by dividing (1) our total assets less our intangible assets and our total liabilities by (2) the number of ordinary shares outstanding as of June 30, 2020, or 22,731,122 ordinary shares.

After giving effect to (i) the 6,000 ordinary shares granted as free shares prior to June 30, 2020, which vested and were issued on July 27, 2020, (ii) the €5 million Bpifrance PGE Loan and (iii) the 3,300,000 ordinary shares issued in the July 2020 Private Placement, resulting in net proceeds of €18.8 million, our pro forma number of ordinary shares outstanding as of June 30, 2020 amounted to 26,037,122 and our pro forma net tangible book value (deficit) as of June 30, 2020 was €(3.4) million ($(3.8) million), or €(0.13) per ordinary share (equivalent to $(0.15) per ADS). After giving further effect to our sale of 6,500,000 ordinary shares (including in the form of ADSs) in the offering, assuming an offering price of $14.00 per ADS in the U.S. offering and €11.56 per ordinary share in the European offering which is the midpoint of the price range set forth on the cover page of this prospectus, and after deducting estimated underwriting commissions and estimated offering expenses payable by us, our pro forma as adjusted net tangible book value at June 30, 2020 would have been €62.3 million ($75.8 million), or €1.92 per ordinary share (equivalent to $2.33 per ADS). This represents an immediate increase in pro forma as adjusted net tangible book value of €2.05 per ordinary share (equivalent to $2.48 per ADS) to existing shareholders and an immediate dilution in pro forma as adjusted net tangible book value of €9.64 per ordinary share (equivalent to $11.67 per ADS) to new investors.

The following table illustrates this dilution on a per ordinary share and per ADS basis:

The dilution information discussed above is illustrative only and will change based on the actual offering price and other terms of the offering determined at pricing. Each €1.00 ($1.2109) increase or decrease in the assumed offering price of €11.56 per ordinary share ($14.00 per ADS), would increase or decrease our pro forma as adjusted net tangible book value by approximately €6.0 ($7.3) million, or approximately €0.19 per ordinary share (equivalent to $0.22 per ADS). For an increase of €1.00 ($1.2109) the dilution to new investors participating in the offering would be approximately €10.46 per ordinary share (equivalent to $12.66 per ADS) and for a decrease of €1.00 ($1.2109) the dilution to new investors participating in the offering would be approximately €8.83 per ordinary share (equivalent to $10.69 per ADS),

assuming that the number of ordinary shares offered by us (including ordinary shares in the form of ADSs), as set forth on the cover page of this prospectus, remains the same, and after deducting estimated underwriting commissions and estimated offering expenses payable by us.

Subject to applicable law, we may also increase or decrease the number of ordinary shares (including ordinary shares in the form of ADSs) we are offering. An increase of 1,000,000 ordinary shares (including ordinary shares in the form of ADSs) offered by us would increase the pro forma as adjusted net tangible book value by approximately €10.8 million ($13.0 million), or €0.32 per ordinary share (equivalent to $0.39 per ADS), and the dilution to new investors participating in the offering would be €9.37 per ordinary share (equivalent to $11.35 per ADS), assuming that the assumed offering price per ADS or ordinary share remains the same, and after deducting estimated underwriting commissions and estimated offering expenses payable by us. Similarly, a decrease of 1,000,000 ordinary shares (including ordinary shares in the form of ADSs) offered by us would decrease the pro forma as adjusted net tangible book value by approximately €10.8 ($13.0) million, or €0.34 per ordinary share (equivalent to $0.41 per ADS), and the dilution to new investors participating in the offering would be €9.92 per ordinary share (equivalent to $12.01 per ADS), assuming that the assumed offering price per ADS or ordinary share remains the same, and after deducting estimated underwriting commissions and estimated offering expenses payable by us.

If we issue 975,000 additional ordinary shares (including in the form of ADSs) pursuant to the exercise in full of the underwriters’ option, the pro forma as adjusted net tangible book value after the offering would be €2.17 per ordinary share (equivalent to $2.64 per ADS), the increase in the pro forma as adjusted net tangible book value to existing shareholders would be €2.30 per ordinary share (equivalent to $2.79 per ADS), and the dilution to new investors participating in the offering would be €9.38 per ordinary share (equivalent to $11.36 per ADS).

The following table sets forth, on a pro forma as adjusted basis as of June 30, 2020, consideration paid to us in cash for ordinary shares (including ordinary shares in the form of ADSs) purchased from us in the past five years by our existing shareholders and by new investors participating in the offering based on an assumed offering price of $14.00 per ADS in the U.S. offering and €11.56 per ordinary share in the European offering which is the midpoint of the price range set forth on the cover page of this prospectus, and before deducting estimated underwriting commissions and estimated offering expenses payable by us:

Each €1.00 ($1.2109) increase or decrease in the assumed offering price of $14.00 per ADS (€11.56 per ordinary share), would increase or decrease the total consideration paid by new investors participating in the offering by €6.5 million ($7.9 million), assuming that the number of ordinary shares offered by us (including ordinary shares in the form of ADSs), as set forth on the cover page of this prospectus, remains the same, and after deducting estimated underwriting commissions. Subject to applicable law, we may also increase or decrease the number of ordinary shares (including ordinary shares in the form of ADSs) we are offering. Each increase or decrease in 1,000,000 ordinary shares (including ordinary shares in the form of ADSs) offered by us would increase or decrease the total consideration paid by new investors participating in the offering by €11.6 ($14.0) million, assuming that the assumed offering price per ADS or ordinary share remains the same and before deducting estimated underwriting commissions. The pro forma as adjusted information discussed above is illustrative only and will be adjusted based on the actual offering price, the actual number of ordinary shares offered by us (including ordinary shares in the form of ADSs) and other terms of the offering determined at pricing.

The table above assumes no issuance by us of additional ordinary shares (including in the form of ADSs) pursuant to the exercise of the underwriters’ option. If we issue additional ordinary shares (including in the form of ADSs) pursuant to the

exercise in full of the underwriters’ option, the number of ordinary shares (including ordinary shares in the form of ADSs) held by the existing shareholders after the offering would be reduced to 52% of the total number of ordinary shares (including ordinary shares in the form of ADSs) outstanding after the offering, and the number of ordinary shares (including ordinary shares in the form of ADSs) held by new investors participating in the offering would increase to 48% of the total number of ordinary shares (including ordinary shares in the form of ADSs) outstanding after the offering.

The tables and calculations above are based on the number of ordinary shares (including in the form of ADSs) that will be outstanding after the offering, which is based on 22,731,122 actual ordinary shares outstanding as of June 30, 2020, before giving effect to the pro forma items described above, and excludes: 

As of September 30, 2020, there were 26,037,122 ordinary shares outstanding, which reflects the 6,000 ordinary shares granted as free shares prior to June 30, 2020, which vested and were issued on July 27, 2020, and the 3,300,000 ordinary shares issued in the July 2020 Private Placement.

The following selected statement of consolidated operations data for the years ended December 31, 2019 and 2018 and selected statement of consolidated financial position data as of December 31, 2019 and 2018 have been derived from our audited consolidated financial statements included elsewhere in this prospectus. Our audited consolidated financial statements have been prepared in accordance with International Financial Reporting Standards (“IFRS”), as issued by the International Accounting Standards Board (“IASB”).

The following selected statement of consolidated operations data for the six months ended June 30, 2020 and 2019 and selected statement of consolidated financial position data as of June 30, 2020 have been derived from our unaudited condensed consolidated interim financial statements as of June 30, 2020 and for the six months ended June 30, 2020 and 2019 included elsewhere in this prospectus. The unaudited condensed consolidated interim financial statements were prepared in accordance with IAS 34, Interim Financial Reporting.

The following selected consolidated financial data for the periods and as of the dates indicated are qualified by reference to, and should be read in conjunction with, our consolidated financial statements and related notes beginning on page F-1 of this prospectus, as well as the section titled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” included elsewhere in this prospectus.

Our historical results for any prior period do not necessarily indicate our results to be expected for any future period and our results for the six months ended June 30, 2020 are not necessarily indicative of the results that may be expected for the full year ending December 31, 2020.

The following discussion of our financial condition and results of operations should be read in conjunction with our unaudited interim condensed consolidated financial statements and year-end audited consolidated financial statements and the related notes included elsewhere in this prospectus. This discussion contains forward-looking statements that reflect our current plans, estimates and strategies. Forward-looking statements involve risks and uncertainties. Our actual results, and the timing of events, could differ materially from those discussed in these forward-looking statements. Factors that could cause or contribute to these differences include those discussed below and elsewhere in this prospectus, particularly under the “Risk Factors” and “Special Note Regarding Forward-Looking Statements” sections.

We are a clinical-stage biotechnology company focused on developing first-in-class product candidates that use our proprietary nanotechnology to transform cancer treatment by increasing the efficacy of radiotherapy. Our lead product candidate, NBTXR3, is an aqueous suspension of functionalized crystalline hafnium oxide nanoparticles designed for injection directly into a malignant tumor prior to standard radiotherapy. When exposed to ionizing radiation, NBTXR3 amplifies the localized, intratumor killing effect of that radiation and may also prime the body’s immune response to fight the cancer. NBTXR3 is designed to enhance the overall efficacy of radiotherapy without resulting in additional side effects on the surrounding healthy tissues.

As of the date of this prospectus, we have administered NBTXR3 to more than 230 patients. We and our collaborators are currently conducting a total of eight clinical trials worldwide to evaluate NBTXR3 as a potential treatment in various cancer indications. In December 2018, we entered into a collaboration with the University of Texas MD Anderson Cancer Center (“MD Anderson”) pursuant to which we intend to launch in the United States of a total of nine NBTXR3 clinical trials across several cancer types, with a total of approximately 340 patients expected to be enrolled across the nine clinical trials. The first clinical trial under this collaboration—a Phase I study in patients with locally advanced or borderline resectable pancreatic cancer—has commenced enrollment with the first patient dosed in September 2020.

We achieved a major proof-of-concept milestone for NBTXR3 with the completion of our randomized, controlled Phase II/III clinical trial in the European Union (the “EU”) for the treatment of patients with locally advanced soft tissue sarcoma (“STS”) of the extremities and trunk wall. This trial yielded positive results and, in April 2019, we completed the regulatory process for the CE mark of NBTXR3, thereby allowing the product to be commercialized in the 27 EU countries for the treatment of locally advanced STS under the brand name Hensify^®.

We are now prioritizing the development of NBTXR3 in the United States and the EU for the treatment of patients with locally advanced head and neck cancers ineligible for chemotherapy, which we believe presents a significant opportunity for NBTXR3 because of the high incidence of these cancers and the significant unmet medical need for such patients. More than half of locally advanced head and neck cancers include large primary tumors which may invade underlying structures, spread to regional nodes or both. Moreover, approximately 50% of patients with locally advanced head and neck cancer who are unable to receive chemotherapy succumb to their cancer within 12 months from the start of radiotherapy. Further, because treatment of locally advanced forms of head and neck cancer ordinarily requires aggressive, concerted measures, the subpopulation of elderly patients generally suffers from limited therapeutic options. Accordingly, we believe NBTXR3 could represent a significant benefit for this patient population with the potential to extend survival and improve quality of life.

As of September 30, 2020, we had cash and cash equivalents of €42.4 million. This includes (i) aggregate net proceeds of €18.8 million received in July 2020 through a capital increase by issuing and selling ordinary shares, (ii) €5 million in proceeds from a PGE loan with Bpifrance received in July 2020 and (iii) €2.3 million in refunds received in July 2020 for a research tax credit related to the taxable year 2019. See “—Liquidity and Capital Resources” below for additional information. For the nine months ended September 30, 2020 and 2019, we had total revenues of approximately €51.6 thousand and €48.2 thousand, respectively.

We have not generated significant revenues to date from product sales or royalties, and we do not expect to generate significant revenues from product sales or royalties unless and until our product candidates are approved for marketing and successfully commercialized. Historically, we have financed our operations and growth through issuances of new shares, refunds of research tax credits, conditional advances and grants awarded by governmental agencies, as well as

bank loans from time to time. From our inception in 2003 through June 30, 2020, we have received more than €221.5 million in financing in the form of external fundraising, loans and repayable advances. See “—Liquidity and Capital Resources” below for additional information.

Since our inception, we have recorded operating losses every year, due primarily to research and development expenses incurred in connection with our efforts to advance our development program for NBTXR3. Our net losses were €50.9 million and €30.3 million for the years ended December 31, 2019 and 2018, respectively, and €20.6 million and €23.9 million for the six-month periods ended June 30, 2020 and 2019, respectively. Our net losses may fluctuate significantly from year to year, depending on the timing of our clinical trials and our expenditures on other research and development activities. We anticipate that our expenses and capital requirements will increase substantially in connection with our ongoing activities, as we: 

Until such time that we can generate substantial revenue from product sales, we expect to finance these expenses and our operating activities through a combination of our existing liquidity and the proceeds of this offering. If we are unable to generate revenue from product sales in accordance with our expected timeframes and in the amounts we expect, or if we otherwise need additional capital to fund our operating activities, we will need to raise additional capital through the issuance of shares, through other equity or debt financings or through collaborations or partnerships with other companies. We may be unable to raise additional funds or enter into such arrangements when needed on favorable terms, or at all, which would have a negative impact on our financial condition and could force us to delay, limit, reduce or terminate our development programs or commercialization efforts or grant to others rights to develop or market product candidates that we would otherwise prefer to develop and market ourselves. Failure to secure adequate funding could cause us to cease operations, in part or in full.

Although it is difficult to predict future liquidity requirements, we expect that the net proceeds from this offering, together with our existing cash and cash equivalents, will be sufficient to fund our current operations through the end of 2022. However, this estimate is based on assumptions that may prove to be wrong, and we could use our capital resources sooner than we currently expect. In any event, we will need additional capital to pursue preclinical and clinical activities, obtain regulatory approval for, and to commercialize our product candidates. Our ability to successfully transition to profitability will be dependent upon achieving a level of revenues adequate to support our cost structure. We cannot assure you that we will ever be profitable or generate positive cash flow from operating activities.

We operate in a single operating segment for accounting purposes. The unaudited interim condensed consolidated financial statements and audited year-end consolidated financial statements have been prepared in accordance with IFRS, International Accounting Standards (“IAS”), as issued by the International Accounting Standards Board (“IASB”), as well as interpretations issued by the IFRS Interpretations Committee (“IFRS-IC”) and the Standard Interpretations Committee (the “SIC”), which application is mandatory as of January 1, 2020. The unaudited interim condensed consolidated financial statements and audited year-end consolidated financial statements are also compliant with IFRS as adopted by the European Union.

Our limited revenues are derived mainly from the charging-back of external contract research organization costs that we incur on behalf of PharmaEngine in connection with the development support we receive as part of our license and collaboration agreement with PharmaEngine.

Our other income consists of grants and subsidies from government agencies and refundable research tax credits.

We have received various grants and other assistance from the government of France and French public authorities, including through Bpifrance (formerly OSEO Innovation), since our creation. The funds are intended to finance our operations or specific projects. Grants and subsidies are recognized in income as the corresponding expenses are incurred and independently of cash flows received.

The French tax authorities grant a research tax credit (Crédit d’Impôt Recherche) to companies in order to encourage them to conduct technical and scientific research. Companies demonstrating that they have incurred research expenditures that meet the required criteria in France (or, since January 1, 2005, other countries in the European Union or the European Economic Area that have signed a tax treaty with France containing an administrative assistance clause) receive a tax credit that may be used for the payment of their income tax due for the fiscal year in which the expenditures were incurred and during the three fiscal years thereafter. If taxes due are not sufficient to cover the full amount of the tax credit at the end of the three-year period, the difference is repaid in cash to the company by the French tax authorities.

The main characteristics of the research tax credits are as follows:

We apply for the research tax credit for research expenses incurred in each fiscal year and recognize the amounts claimed in the same fiscal year. We have concluded that the research tax credits meet the definition of a government grant as defined in IAS 20, Accounting for Government Grants and Disclosure of Government Assistance, and, as a result, it has been classified as “Other income” within operating income in our statements of consolidated operations.

Our operating expenses are primarily incurred for research and development and selling, general and administrative purposes, for the most part in France.

Research and development activities are central to our business. Since our inception, most of our resources have been allocated to research and development. These expenses include:

Product candidates in later stages of clinical development generally have higher development costs than those in earlier stages, primarily due to the increased size and duration of later-stage clinical trials. We expect that our research and development expenses will continue to increase in the foreseeable future as we advance the clinical development of NBTXR3.

We cannot determine with certainty the duration and completion costs of the current or planned future clinical trials of our product candidates or if, when, or to what extent we will generate revenue from the commercialization and sale of any of our product candidates that obtain regulatory approval. We may not succeed in achieving regulatory approval for any particular product candidate. The duration, costs and timing of clinical trials and development of our product candidates will depend on a variety of factors, including:

A change in the outcome of any of these variables with respect to the development of NBTXR3 or any other product candidate that we develop could mean a significant change in the costs and timing associated with the development of NBTXR3 or such other product candidates. For example, if the FDA or other comparable regulatory authority were to require us to conduct preclinical studies and clinical trials beyond those which we currently anticipate will be required for the completion of clinical development, or if we experience significant delays in enrollment in any clinical trials, we could be required to spend significant additional financial resources and time on clinical development.

SG&A expenses mainly comprise administrative payroll costs, overhead costs relating to our headquarters in Paris, and costs such as accounting, legal, human resources, communications and market access activities.

We anticipate that our SG&A expenses will increase in the future as we increase our headcount to support the expected growth in our research and development activities and the potential commercialization of NBTXR3. We also anticipate increased expenses associated with being a public company in the United States, including costs related to audit, legal, regulatory and tax-related services associated with maintaining compliance with Nasdaq listing and SEC requirements, director and officer insurance premiums, and investor relations costs. In particular, we will need to incur additional

accounting expenses to comply with the Sarbanes-Oxley Act of 2002 in the United States, which will require us to test the effectiveness of our internal controls over financial reporting.

Net financial income (loss) comprises mainly interest income on short-term bank deposits, interest costs primarily on our loan from the EIB (the “EIB loan”), foreign exchange gains and losses and, since January 1, 2019, the interest costs on leases related to the application of IFRS 16. See Note 2 of our unaudited interim condensed consolidated financial statements and year-end audited consolidated financial statements for additional details regarding IFRS 16 lease liabilities.

We apply significant judgments to determine the amount and timing of revenue under our license and collaboration agreement with PharmaEngine, mainly with respect to identifying our performance obligations and determining the timing of satisfaction of support services provided to PharmaEngine.

See Note 15 of our unaudited interim condensed consolidated financial statements and audited year-end consolidated financial statements for additional detail regarding our accounting policies for our sources of revenue.

Deferred taxes are recognized for temporary differences arising from the difference between the tax basis and the accounting basis of our assets and liabilities that appear in our financial statements. The primary temporary differences are related to the tax losses that can be carried forward or backward depending on the jurisdiction. Enacted tax rates are used to measure deferred taxes.

Deferred tax assets are recorded in the accounts only to the extent that it is probable that the future profits will be sufficient to absorb the losses that can be carried forward or backward. Considering our stage of development, which does not allow income projections judged to be sufficiently reliable to be made, we have not recognized deferred tax assets in relation to tax losses carryforwards in the statements of consolidated financial position.

We measure the fair value of stock options, founders’ warrants, and other warrants granted to employees, members of our executive board and supervisory board and consultants based on actuarial models. These actuarial models require that we use certain calculation assumptions with respect to characteristics of the grants, such as vesting terms, and market data, such as expected share volatility.

Clinical trial expenses, although not yet billed in full, are estimated for each trial and an accrual is recognized accordingly. See Note 13.1 of our unaudited interim condensed consolidated financial statements and audited year-end consolidated financial statements for information regarding the clinical trial accruals.

The fair value measurement of the EIB loan requires us to assess the amount of additional interest (“royalties,” as defined in the royalty agreement with EIB) that will be due according to the royalty agreement during a royalty calculation period commencing on January 1, 2021. The royalties due during this period will be determined and calculated based on the number of tranches that have been withdrawn and will be indexed to our annual sales turnover. For purposes of measuring the fair value of the EIB loan, we forecast the sales that we expect to generate during the six-year royalty calculation period, taking into consideration our operational assumptions such as anticipated market release dates of our products, growth and penetration rate in each market. This forecast depends on our ability to