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As filed with the Securities and Exchange Commission on June 2, 2020

Registration No. 333-            

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

Form F-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

CELLECTIS S.A.

(Exact Name of Registrant as Specified in Its Charter)

Cellectis S.A.

8, rue de la Croix Jarry

75013 Paris, France

Tel. +33 (0)1 81 69 16 00

(Address and telephone number of Registrant’s principal executive offices)

Cellectis, Inc.

430 East 29th Street

New York, New York 10016

(347) 908-5980

(Name, address, and telephone number of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: From time to time after the effective date of this registration statement.

If only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box.  ☐

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box  ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a registration statement pursuant to General Instruction I.C. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.  ☒

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.C. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.  ☐

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act.

Emerging growth company  ☐

If an emerging growth company that prepares its financial statements in accordance with U.S. Generally Accepted Accounting Principles (GAAP), indicate by check mark if the registrant has elected not to use the extended transition period for comply with any new or revised financial accounting standards† provided pursuant to Section 7(a)(2)(B) of Securities Act.  ☐

† The term “new or revised financial accounting standard” refers to any update issued by the Financial Accounting Standards Board to its Accounting Standards Codification after April 5, 2012.

CALCULATION OF REGISTRATION FEE

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PROSPECTUS

Ordinary Shares

Preferred Shares

Warrants

We may offer from time to time the securities described in this prospectus, either individually or in any combination, in one or more offerings at prices and on terms that will be determined at the time of the offering.

We may offer and sell these securities on a continuous or delayed basis to or through one or more underwriters, dealers and agents, or directly to purchasers, or through any combination of these methods. For additional information on the methods of sale, you should refer to the section entitled “Plan of Distribution” in this prospectus.

Other than any securities sold in connection with a rights offering, we will only sell securities pursuant to this prospectus for which preferential subscription rights shall have been waived by our shareholders in accordance with French law.

Our ordinary shares will be sold in the form of American Depositary Shares, or ADSs. Each ADS represents one ordinary share. Our ADSs are listed on the Nasdaq Global Market under the symbol “CLLS”. On June 1, 2020, the last reported sale price of our ADSs was $18.69 per ADS.

The applicable prospectus supplement will contain information, where applicable, as to any other listing on the Nasdaq Global Market or any other securities market or other exchange with respect to the securities covered by such prospectus supplement. The preferred shares and warrants described in this prospectus have not been approved for listing on any market or exchange, and we have not made any application for such listing.

This prospectus describes the general terms of the securities we may offer and the general manner in which we may offer these securities. We will provide the specific terms of any offering of securities in one or more supplements to this prospectus. Such prospectus supplements may also add, update or change information contained in this prospectus. You should carefully read this prospectus and the applicable prospectus supplement, together with the documents we incorporate by reference, before you invest. This prospectus may not be used to consummate a sale of securities unless accompanies by the applicable prospectus supplement.

Investing in our securities involves risks. See “Risk Factors”.

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

The date of this prospectus is June 2, 2020.

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ABOUT THIS PROSPECTUS

This prospectus relates to the sale of our ordinary shares in the form of ADSs, preferred shares or warrants, either individually or in any combination.

This prospectus is part of a registration statement that we filed with the United States Securities and Exchange Commission (the “SEC”) using a “shelf” registration process. Under the shelf process, we may sell the securities described in this prospectus from time to time in the future in one or more offerings.

This prospectus only provides you with a general description of the securities we may offer. Each time we sell securities described herein, we will provide prospective investors with a supplement to this prospectus that will contain specific information about the terms of that offering, including the specific amounts, prices and terms of the securities offered. The prospectus supplement may also add to, update or change information contained in this prospectus. Accordingly, to the extent inconsistent, information in this prospectus is superseded by the information in any prospectus supplement. You should carefully read both this prospectus and any accompanying prospectus supplement, together with the information incorporated by reference and any other offering materials. See “Where You Can Find More Information” and “Incorporation of Information by Reference.”

Unless otherwise indicated or the context otherwise requires, references in this prospectus to “Cellectis,” “the Company,” “we,” “us,” and “our” refer to Cellectis S.A. and its consolidated subsidiaries. All references in this prospectus to “$,” “U.S. dollars,” “dollars” and “USD” mean U.S. dollars and all references to “€” and “euros” mean euros, unless otherwise noted. References to “Calyxt” refer to our majority-owned subsidiary, Calyxt, Inc.

We have not authorized anyone to provide any information other than that contained in this prospectus, any applicable prospectus supplement or in any free writing prospectus prepared by or on behalf of us to which we have referred you. We have not authorized any other person to provide you with different information. We take no responsibility for, and provide no assurances as to the reliability of, any other information that others may give you.

You should assume that the information in this prospectus, any applicable prospectus supplement, any document incorporated by reference herein or therein, and any free writing prospectus prepared by or on behalf of us to which we have referred you is accurate only as of the respective date on the front of the applicable document, regardless of the time of delivery. Our business, financial condition, results of operations and prospects may have changed since that date.

We are not making an offer to sell or a solicitation of an offer to buy any securities described herein in any jurisdiction in which an offer or solicitation is not permitted or in which the person making that offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make an offer or solicitation.

For investors outside the United States: We have not done anything that would permit this 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 securities described herein and the distribution of this prospectus outside the United States.

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TRADEMARKS

We own various trademark registrations and applications, and unregistered trademarks and service marks, including “Cellectis^®”, “TALEN^®” and our corporate logos, and all such trademarks and service marks appearing in this prospectus and any prospectus supplement are the property of Cellectis. The trademark Calyxt is owned by Calyxt. All other trade names, trademarks and service marks of other companies appearing in this prospectus or any prospectus supplement are the property of their respective holders. Solely for convenience, the trademarks and trade names in this prospectus and any prospectus supplement may be referred to without the ^® and ^™ symbols, but such references, or the failure of such symbols to appear, should not be construed as any indication that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto. We do not intend to use or display other companies’ trademarks and trade names to imply a relationship with, or endorsement or sponsorship of us by, any other companies.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and any prospectus supplement contain and incorporate by reference “forward-looking statements” within the meaning of applicable federal securities laws, including the Private Securities Litigation Reform Act of 1995. All statements other than present and historical facts and conditions, including statements regarding our future results of operations and financial position, business strategy, plans and our objectives for future operations, are forward-looking statements. We use words such as “anticipate,” “believe,” “can,” “could,” “estimate,” “expect,” “intend,” “is designed to,” “may,” “might,” “plan,” “potential,” “predict,” “objective,” “should,” or the negative of these and similar expressions to identify forward-looking statements.

Forward-looking statements are made in light of information currently available to us and represent our current judgment on what the future may hold. However, these statements are not guarantees of any events or financial results, and our actual results may differ materially due to numerous important factors and uncertainties. Many important factors, in addition to the factors described in this prospectus and any prospectus supplement, which may adversely affect such forward-looking statements are set forth in Part I, Item 3.D. of our Annual Report on Form 20-F for the fiscal year ended December 31, 2019, as updated by our subsequent Annual Reports on Form 20-F, Current Reports on Form 6-K and the other documents incorporated by reference herein. See “Where You Can Find More Information” and “Incorporation of Information by Reference.” Many of these risks, uncertainties and assumptions are beyond our control, and may cause our actual results and performance to differ materially from our expectations. Accordingly, you should not place undue reliance on any forward-looking statements contained or incorporated by reference in this prospectus, the applicable prospectus supplement or the documents incorporated by reference herein and therein.

Forward-looking statements apply only as of the date they are made. Except as required by law, we undertake no obligation to revise or update any forward-looking statements to reflect events or circumstances that arise after the date the forward-looking statement is made.

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CELLECTIS S.A.

We are a clinical stage biotechnological company, employing our core proprietary technologies to develop best-in-class products in the field of immuno-oncology. Our product candidates, based on gene-edited T-cells that express chimeric antigen receptors, or CARs, seek to harness the power of the immune system to target and eradicate cancer cells. We believe that CAR-based immunotherapy is one of the most promising areas of cancer research, representing a new paradigm for cancer treatment. We are designing next-generation immunotherapies that are based on gene-edited CAR T-cells. Our gene-editing technologies allow us to create allogeneic CAR T-cells, meaning they are derived from healthy donors rather than the patients themselves. We believe that the production of allogeneic CAR T-cells will allow us to develop cost-effective, off-the-shelf products that are capable of being cryopreserved, stored and distributed worldwide. Our gene-editing expertise also enables us to develop product candidates that feature additional safety and efficacy attributes, including control properties designed to prevent them from attacking healthy tissues, to enable them to tolerate standard oncology treatments, and to equip them to resist mechanisms that inhibit immune-system activity. In addition to our focus on immuno-oncology, we are exploring the use of our gene-editing technologies in other therapeutic applications, as well as to develop, through Calyxt, plant-based solutions designed to be healthy and sustainable.

Our legal and commercial name is Cellectis S.A. We were incorporated as a société anonyme, or S.A., under the laws of the French Republic on January 4, 2000 for a period of 99 years. We are registered at the Paris Registre du Commerce et des Sociétés under the number 428 859 052. Our principal executive offices are located at 8, rue de la Croix Jarry, 75013 Paris, France, and our telephone number is +33 1 81 69 16 00. Our agent for service of process in the United States is Cellectis, Inc. We also maintain a website at www.cellectis.com. The reference to our website is an inactive textual reference only and the information contained in, or that can be accessed through, our website is not a part of this prospectus.

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RISK FACTORS

An investment in our securities involves a high degree of risk. Before deciding whether to purchase our securities, you should carefully consider the risk factors incorporated by reference from our most recent Annual Report on Form 20-F and the other information contained in this prospectus or any applicable prospectus supplement, as updated by those subsequent filings with the SEC under the Securities Exchange Act of 1934, as amended, that are incorporated herein by reference. These risks could materially affect our business, results of operations or financial condition and cause the value of our securities to decline, in which case you may lose all or part of your investment. For more information see “Where You Can Find More Information” and “Incorporation of Information by Reference.”

USE OF PROCEEDS

Unless otherwise set forth in a prospectus supplement, we currently intend to use the net proceeds of any offering of securities for working capital and other general corporate purposes. Accordingly, we will have significant discretion in the use of any net proceeds. We may provide additional information on the use of the net proceeds from the sale of the offered securities in an applicable prospectus supplement relating to the offered securities.

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DESCRIPTION OF SHARE CAPITAL

The following description of our share capital summarizes certain provisions of our By-laws. Such summaries do not purport to be complete and are subject to, and are qualified in their entirety by reference to, all of the provisions of our By-laws, copies of which have been filed with the SEC. Holders of ADSs will be able to exercise their rights with respect to the ordinary shares underlying the ADSs only in accordance with the terms of the deposit agreement. See “Description of American Depositary Shares” for more information.

General

As of December 31, 2019, our outstanding share capital consisted of a total of 42,465,669 issued and fully paid ordinary shares, with nominal value €0.05 per share. We have no preferred shares outstanding.

Under French law, our By-laws set forth only our issued and outstanding share capital as of the date of the By-laws. Our fully diluted share capital represents all issued and outstanding shares, as well as all potential shares which may be issued upon exercise of outstanding employee warrants, employee share options and non-employee warrants, as granted by our board of directors.

We are entitled under French law to issue preferred shares but our By-laws do not currently specify specific characteristics or rights attached to any specific category of preferred shares, which would be determined by the extraordinary general meeting convened for such purpose.

Key Provisions of Our By-laws and French Law

The description below reflects the terms of our By-laws, and summarizes the material rights of holders of our ordinary shares under French law. Please note that this is only a summary and is not intended to be exhaustive. For further information, please refer to the full version of our By-laws which is included as an exhibit to the registration statement of which this prospectus is a part. In the event that our By-laws are modified in connection with the establishment of a specific category of preferred shares, the rights of holders of such preferred shares under our By-laws and French law will be described in the applicable prospectus supplement.

Corporate Purpose

Our corporate purpose, which is set forth in Article 3 of our By-laws, in France and abroad includes:

Directors

Board Composition. Under French law, a société anonyme must have at least three and may have up to 18 directors. The number of directors is fixed by or in the manner provided in the by-laws. The sections of the By-laws relating to the number of directors and election and removal of a director from office may only be modified by a resolution adopted by a two-thirds majority of the votes cast of our shareholders present, represented by a proxy or voting by mail at the meeting. The votes cast do not include votes attached to shares held by shareholders who did not take part in the vote, abstained or voted blank or null. Under French law, directors are elected at the ordinary general shareholders’ meeting by a simple majority vote, and may be removed from office, with or without cause, at any shareholders’ meeting without notice or justification, by a simple majority vote.

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Quorum and Voting. The board of directors may only deliberate if at least half of the directors attend the applicable meeting in the manner provided for in our By-laws. In particular, French law and the charter of the board of directors allow directors to attend meetings of the board of directors in person or, to the extent permitted by applicable law, by videoconference or other telecommunications arrangements. In addition, our By-Laws allow a director to grant another director a proxy to represent him or her at a meeting of the board of directors, but no director can hold more than one proxy at any meeting. Decisions of the board of directors are adopted by the majority of the voting rights held by the directors present or represented, it being specified that in case of a vote-split, the Chairman of the board of directors shall have a deciding vote.

Directors’ Voting Powers on Proposal, Arrangement or Contract in which any Director is Materially Interested. Under French law, any agreement entered into (directly or through an intermediary) between us and any director that is not entered into (1) in the ordinary course of business and (2) under standard terms and conditions is subject to the prior authorization of the board of directors, excluding the vote of the interested director.

The foregoing requirements also apply to agreements between us and another company, provided that the company is not one of our wholly-owned subsidiaries, if one of our directors is the owner or a general partner, manager, director, general manager or member of the executive or supervisory board of the other company, as well as to agreements in which one of our directors has an indirect interest.

Directors’ Compensation. The aggregate amount of compensation (formerly named attendance fees (jetons de présence)) of the board of directors is determined at the shareholders’ annual ordinary general meeting. The board of directors then divides all or part (at the board’s discretion) of this aggregate amount among some or all of its members by a simple majority vote. In addition, the board of directors may grant exceptional compensation (rémunérations exceptionnelles) to a director on a case-by-case basis for special and temporary assignments. The board of directors may also authorize the reimbursement of reasonable travel and accommodation expenses, as well as other expenses incurred by directors in the corporate interest.

Board of Directors’ Borrowing Powers. There are currently no limits imposed by our By-laws on the amounts of loans or borrowings that the board of directors may approve.

Directors’ Age Limits. The number of directors who are more than seventy (70) years old may not exceed one third of the directors in office.

Term of Director Office. Our By-laws provide that members of our board of directors are elected for a three-year term, beginning upon the year of a director’s initial appointment.

Employee Director Limits. The number of directors who are also party to employment contracts with the Company may not exceed one third of the directors in office.

Directors’ Share Ownership Requirements. None.

Rights, Preferences and Restrictions Attaching to Ordinary Shares

Dividends. We may only distribute dividends out of our “distributable profits,” plus any amounts held in our reserves that the shareholders decide to make available for distribution, other than those reserves that are specifically required to be maintained by law. “Distributable profits” consist of our unconsolidated net profit in each fiscal year, as increased or reduced by any profit or loss carried forward from prior years, less any contributions to the reserve accounts pursuant to French law (see below under “—Legal Reserve”).

Legal Reserve. Pursuant to French law, we must allocate at least 5% of our unconsolidated net profit for each year to our legal reserve fund before dividends may be paid with respect to that year. Such allocation is

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compulsory until the amount in the legal reserve is equal to 10% of the aggregate par value of our issued and outstanding share capital. This restriction on the payment of dividends also applies to our French subsidiaries on an unconsolidated basis.

Approval of Dividends. Pursuant to French law, our board of directors may propose a dividend and/or reserve distribution for approval by the shareholders at the annual ordinary general meeting.

Upon recommendation of our board of directors, our shareholders may decide to allocate all or part of any distributable profits to special or general reserves, to carry them forward to the next fiscal year as retained earnings or to allocate them to the shareholders as dividends. However, dividends may not be distributed when as a result of such distribution our net assets are or would become lower than the amount of the share capital plus the amount of the legal reserves which, under French law, may not be distributed to shareholders.

Our board of directors may distribute interim dividends after the end of the fiscal year but before the approval of the financial statements for the relevant fiscal year when the interim balance sheet, established during such year and examined by an auditor, reflects that we have earned distributable profits since the close of the last financial year, after recognizing the necessary depreciation and provisions and after deducting prior losses, if any, and the sums to be allocated to reserves, as required by law or the By-laws, and including any retained earnings. The amount of such interim dividends may not exceed the amount of the profit so defined.

Distribution of Dividends. Dividends are distributed to shareholders proportionally to their shareholding interests. In the case of interim dividends, distributions are made to shareholders on the date set by our board of directors during the meeting in which the distribution of interim dividends is approved. The actual dividend payment date is decided by the shareholders at an ordinary general shareholders’ meeting or by our board of directors in the absence of such a decision by the shareholders. Shareholders that own shares on the actual payment date are entitled to the dividend.

Dividends may be paid in cash or, if the shareholders’ meeting so decides, in kind, provided that all the shareholders receive a whole number of assets of the same nature paid in lieu of cash. Our By-laws provide that, subject to a decision of the shareholders’ meeting taken by ordinary resolution, each shareholder may be given the choice to receive his dividend in cash or in shares.

Timing of Payment. Pursuant to French law, dividends must be paid within a maximum period of nine months following the end of the relevant fiscal year. An extension of such timeframe may be granted by court order. Dividends that are not claimed within a period of five years after the payment date will be deemed to expire and revert to the French state.

Voting Rights. Each of our ordinary shares entitles its holder to vote and be represented in the shareholders’ meetings in accordance with the provisions of French law and of our By-laws. The ownership of a share implies the acceptance of our By-laws and any decision of our shareholders.

In general, each shareholder is entitled to one vote per share at any general shareholders’ meeting. However, our By-Laws provide that all shares held in registered form (actions nominatives) for more than two years will be granted double voting rights.

Under French law, treasury shares or shares held by entities controlled by us are not entitled to voting rights and are not taken into account for purposes of quorum calculation.

Rights to Share in Our Profit. Under French law each ordinary share entitles its holder to a portion of the corporate profits and assets proportional to the amount of share capital represented thereby.

Rights to Share in the Surplus in the Event of Liquidation. If we are liquidated, any assets remaining after payment of our debts, liquidation expenses and all of our remaining obligations will first be used to repay in full the par value of our outstanding shares. Any surplus will then be distributed among shareholders proportionally to their shareholding in our company.

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Repurchase and Redemption of Shares. Under French law, we may acquire our own shares. Such acquisition may be challenged on the ground of market abuse regulations. However, Regulation 596/2014 of April 16, 2014 and its related delegated regulations (MAR) provides for safe harbor exemptions when the acquisition is made (i) under a buy-back program to be authorized by the shareholders in accordance with the provisions of Article L. 225-209 of the French Commercial Code and with the General Regulations of the French Financial Markets Authority (Autorité des marchés financiers or “AMF”) and (ii) for one of the following purposes which shall be provided for in the buy-back program:

In addition, we benefit from a simple exemption when the acquisition is made under a liquidity contract complying with the general regulations of, and market practices accepted by, the AMF.

All other purposes, and especially share buy-backs made for external growth operations in pursuance of Article L. 225-209 of the French Commercial Code, while not forbidden, must be pursued in strict compliance of market manipulation and insider dealing rules.

Under the Market Abuse Regulation 596/2014 of April 16, 2014 (MAR) and in accordance with the General Regulations of the AMF, a corporation shall report to the AMF, no later than by the end of the seventh daily market session following the date of the execution of the transaction, all the transactions relating to the buy-back program, in a detailed form and in an aggregated form. In addition, we shall provide to the AMF, on a monthly basis, and to the public, on a quarterly basis, a summary report of the transactions made under a liquidity contract.

The decision to repurchase shares in order to decrease our share capital shall not be driven by losses and a purchase offer shall be made to all shareholders on a pro rata basis, with the approval of the shareholders at the extraordinary general meeting deciding the capital reduction; in this case, the shares repurchased must be cancelled within one month from their repurchase date.

In any case, no such repurchase of shares may result in us holding, directly or through a person acting on our behalf, more than 10% of our issued share capital. Shares repurchased by us continue to be deemed “issued” under French law but are not entitled to dividends or voting rights so long as we hold them directly or indirectly, and we may not exercise the preemptive rights attached to them.

Sinking Fund Provisions. Our By-laws do not provide for any sinking fund provisions.

Liability to Further Capital Calls. Shareholders are liable for corporate liabilities only up to the par value of the shares they hold; they are not liable to further capital calls.

Requirements for Holdings Exceeding Certain Percentages. There are no such requirements, except as described under the section of this prospectus titled “—Form, Holding and Transfer of Shares—Ownership of Shares and ADSs by Non-French Persons.”

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Actions Necessary to Modify Shareholders’ Rights

Shareholders’ rights may be modified as allowed by French law. Only the extraordinary shareholders’ meeting is authorized to amend any and all provisions of our By-laws. It may not, however, increase any of the shareholders’ commitments without the prior approval of each shareholder.

Special Voting Rights of Warrant Holders

Under French law, the holders of warrants of the same class (i.e., warrants that were issued at the same time and with the same rights), including founders’ warrants, are entitled to vote as a separate class at a general meeting of that class of warrant holders under certain circumstances, principally in connection with any proposed modification of the terms and conditions of the class of warrants or any proposed issuance of preferred shares or any modification of the rights of any outstanding class or series of preferred shares.

Rules for Admission to and Calling Annual Shareholders’ Meetings and Extraordinary Shareholders’ Meetings

Access to, Participation in and Voting Rights at Shareholders’ Meetings. The right to participate in a shareholders’ meeting is granted to all the shareholders, regardless of the number of shares they hold, whose shares are fully paid up and for whom a right to attend shareholders’ meetings has been established by registration of their shares in the names or names of the authorized intermediary acting on their behalf on the second business day prior to the shareholders’ meeting at midnight (Paris time), either in the registered shares accounts held by the Company or in the bearer shares accounts held by the authorized intermediary.

Each shareholder may attend the meetings and vote (1) in person, or (2) by granting a proxy to any person, or (3) by sending a proxy to us without indication of the beneficiary (in which case such proxy shall be cast in favor of the resolutions supported by the board of directors), or (4) by correspondence, or (5) by videoconference or another means of telecommunication organized by the board of directors and allowing identification of the relevant shareholder in accordance with applicable laws.

Shareholders may, in accordance with legal and regulatory requirements, send their vote or proxy, either by hard copy or via telecommunications means. Such vote or proxy must be received (1) at least three days prior to the meeting, in the case of hard copies, (2) by 3:00 p.m. (Paris time) on the day before the meeting, in the case of, electronic votes by email, (3) by the date of the meeting, in the case of a proxy granted to a designated person, and (4) by 3:00 p.m. (Paris time) on the day before the meeting, in the case of proxies without a designated attorney and therefore granted to the chairman of the meeting.

Shareholders sending their vote within the applicable time limit, using the form provided to them by us for this purpose, are deemed present or represented at the shareholders’ meeting for purposes of quorum and majority calculation.

The voting by correspondence form addressed by a shareholder is only valid for a single meeting or for successive meetings convened with the same agenda.

Notice of Annual Shareholders’ Meetings. Shareholders’ meetings are convened by our board of directors, or, failing that, by our statutory auditors, or by a court appointed agent or liquidator in certain circumstances, or by the majority shareholder in capital or voting rights following a public tender offer or exchange offer or the transfer of a controlling block on the date decided by the board of directors or the relevant person. Meetings are held at our registered offices or at any other location indicated in the convening notice. A meeting notice (avis de réunion) is published in the French Journal of Mandatory Statutory Notices (BALO) at least 35 days prior to the date of the shareholders’ meeting.

Additionally, a convening notice (avis de convocation) is published at least fifteen days prior to the date of the meeting in a legal gazette of the department in which the registered office of the company is located and in

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the French Journal of Mandatory Statutory Notices (BALO). Further, shareholders having held registered shares (actions nominatives) for at least one month at the time of the convening notice must be convened individually, by regular letter (or by registered letter if requested by the relevant shareholder) sent to their last known address.

When the shareholders’ meeting cannot deliberate due to the lack of the required quorum, the second meeting must be called at least ten days in advance in the same manner as used for the first notice.

All notices to the shareholders must further specify the conditions under which the shareholders may vote by correspondence.

Agenda and Conduct of Annual Shareholders’ Meetings. The agenda of the shareholders’ meeting shall appear in the notice to convene the meeting. The shareholders’ meeting may only deliberate on the items on the agenda except for the removal of directors and the appointment of their successors, which may be put to vote by any shareholder during any shareholders’ meeting. One or more shareholders representing the percentage of share capital required by French law (currently 5%), and acting in accordance with legal requirements and within applicable time limits, may request the inclusion of items or proposed resolutions on the agenda.

Shareholders’ meetings shall be chaired by the Chairman of the board of directors or, in his or her absence, by a director appointed for this purpose by the board of directors; failing which, the meeting itself shall elect a Chairman. Vote counting shall be performed by the two members of the meeting who are present and accept such duties, who represent, either on their own behalf or as proxies, the greatest number of votes.

Ordinary Shareholders’ Meeting. Ordinary shareholders’ meetings are those meetings called to make any and all decisions that do not result in a modification of our By-laws. An ordinary shareholders’ meeting shall be convened at least once a year within six months of the end of each fiscal year in order to approve the annual and consolidated accounts for the relevant fiscal year or, in case of postponement, within the period established by court order. Upon first notice, the meeting may validly deliberate only if the shareholders present or represented by proxy or voting by mail represent at least one-fifth of the shares entitled to vote. Upon second notice, no quorum is required. Decisions are made by a majority of the votes cast of the shareholders present, represented by proxy, or voting by mail. The votes cast do not include votes attached to shares held by shareholders who did not take part in the vote, abstained or voted blank or null.

Extraordinary Shareholders’ Meeting. Only an extraordinary shareholders’ meeting is authorized to amend our By-laws. It may not, however, increase shareholders’ commitments without the approval of each shareholder. Subject to the legal provisions governing share capital increases from reserves, profits or share premiums, the resolutions of the extraordinary meeting will be valid only if the shareholders present, represented by proxy or voting by mail represent at least one-fourth of all shares entitled to vote upon first notice, or one-fifth upon second notice. If the latter quorum is not reached, the second meeting may be postponed to a date no later than two months after the date for which it was initially called. Decisions are made by a two-thirds majority of the votes cast of the shareholders present, represented by proxy, or voting by mail. The votes cast do not include votes attached to shares held by shareholders who did not take part in the vote, abstained or voted blank or null.

In addition to the right to obtain certain information regarding us at any time, any shareholder may, from the date on which a shareholders’ meeting is convened until the fourth business day preceding the date of the shareholders’ meeting, submit written questions relating to the agenda for the meeting to our board of directors. Our board of directors is required to respond to these questions during the meeting, except if the answers of the board are posted on the website of the Company at the latest at the end of the shareholders’ meeting. The board of directors may delegate one of its members, the chief executive officer or a deputy chief executive officer, as the case may be, to respond.

Provisions Having the Effect of Delaying, Deferring or Preventing a Change in Control of the Company

Provisions contained in our By-laws and the corporate laws of France, the country in which we are incorporated, could make it more difficult for a third-party to acquire us, even if doing so might be beneficial to

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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:

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Declaration of Crossing of Ownership Thresholds

Subject to requirements of French law, our By-laws do not require any specified disclosure by shareholders that cross ownership thresholds with respect to our share capital, except as described under the section of this prospectus titled “—Form, Holding and Transfer of Shares—Ownership of Shares and ADSs by Non-French Persons.”

The absence of specific requirement in our By-laws is without prejudice to the following disclosures which are applicable to us according to French legal and regulatory provisions, it being provided that the following is a summary which is therefore not intended to be a complete description of applicable rules under French law:

The above obligations of declaration apply when crossing each of the above-mentioned thresholds in an upward or downward direction.

In case of failure to declare shares or voting rights exceeding the fraction that should have been declared, such shares shall be deprived of voting rights at shareholders’ meetings for any meeting that would be held until the expiry of a period of two years from the date of regularization of the notification in accordance with Article L. 233-14 of the French Commercial Code. Additional sanctions may apply pursuant to Article L. 621-15 of the French Monetary and Financial Code.

Subject to certain exemptions, any shareholder crossing, alone or acting in concert, the 50% threshold must file a mandatory public tender offer.

Changes in Share Capital

Increases in Share Capital. Pursuant to French law, our share capital may be increased only with shareholders’ approval at an extraordinary general shareholders’ meeting following the recommendation of our board of directors. The shareholders may delegate to our board of directors either the authority (délégation de compétence) or the power (délégation de pouvoir) to carry out any increase in share capital in accordance with applicable laws.

Increases in our share capital may be effected by:

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Increases in share capital by issuing additional securities may be effected through one or a combination of the following:

Decisions to increase the share capital through the capitalization of reserves, profits and/or share premium require shareholders’ approval at an extraordinary general shareholders’ meeting, acting under the quorum and majority requirements applicable to ordinary shareholders’ meetings. Increases in share capital effected by an increase in the par value of shares require unanimous approval of the shareholders, unless effected by capitalization of reserves, profits or share premium. All other capital increases require shareholders’ approval at an extraordinary general shareholders’ meeting acting under the regular quorum and majority requirements for such meetings.

Reduction in Share Capital. Pursuant to French law, any reduction in our share capital requires shareholders’ approval at an extraordinary general shareholders’ meeting following the recommendation of our board of directors. The share capital may be reduced either by decreasing the par value of the outstanding shares or by reducing the number of outstanding shares. The number of outstanding shares may be reduced by the repurchase and cancellation of shares. Holders of each class of shares must be treated equally unless each affected shareholder agrees otherwise.

Preferential Subscription Right (Preemptive Rights). According to French law, if we issue additional shares or securities giving right, immediately or in the future, to new shares for cash, current shareholders will have preferential subscription rights to these securities on a pro rata basis. Preferential subscription rights entitle the individual or entity that holds them to subscribe proportionally to the number of shares held by them to the issuance of any securities increasing, or that may result in an increase of, our share capital by means of a cash payment or a set-off of cash debts. The preferential subscription rights may be transferred and/or sold during the subscription period relating to a particular offering. Pursuant to French law, the preferential subscription rights will be transferable during a period starting two working days prior to the opening of the subscription period and ending two working days prior to the closing of the subscription period.

The preferential subscription rights with respect to any particular offering may be waived at an extraordinary general meeting by a two-thirds majority of the vote cast of our shareholders or individually by each shareholder. Our board of directors and our independent auditors are required by French law to present reports to the shareholders’ meeting that specifically address any proposal to waive the preferential subscription rights.

Further, to the extent permitted under French law, we may seek, during an extraordinary general shareholders’ meeting, the approval of the shareholders to waive their preferential subscription rights in order to authorize the board of directors to issue additional shares and/or other securities convertible or exchangeable into shares.

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Form, Holding and Transfer of Shares—Ownership of Shares and ADSs by Non-French Persons

Form of Shares. Pursuant to our By-laws, shares may be held in registered or bearer form, at each shareholder’s discretion.

Further, in accordance with applicable legal and regulatory provisions, we may request at any time from the authorized intermediary responsible for holding our shares the name or, in the case of a legal entity, the corporate name, nationality and address of holders of securities, giving immediate or future access to voting rights at our shareholders’ meetings, the number of securities they own and, where applicable, the restrictions attaching to such securities.

Holding of Shares. In accordance with French law concerning the “dematerialization” of securities, the ownership rights of shareholders are represented by book entries instead of share certificates. Shares are registered in individual accounts opened by us or any authorized intermediary, in the name of each shareholder and kept according to applicable legal and regulatory provisions.

Ownership of Shares and ADSs by Non-French Persons. Neither the French Commercial Code nor our By-laws presently impose any restrictions on the right of non-French residents or non-French shareholders to own and vote shares.

However, non-French residents must file a declaration for statistical purposes with the Bank of France (Banque de France) within twenty working days following the date of certain direct foreign investments in us, including any purchase of our ADSs. In particular, such filings are required in connection with investments exceeding €15,000,000 that lead to the acquisition of at least 10% of our Company’s share capital or voting rights or cross such 10% threshold. Violation of this filing requirement may be sanctioned by five years of imprisonment and a fine of up to twice the amount of the relevant investment. This amount may be increased fivefold if the violation is made by a legal entity.

Further, any investment (i) by an individual or entity located in a country that is not a member State of the European Union or of a member State of the European Economic Area having entered into a convention on administrative assistance against tax evasion and fraud with France, or by a French citizen not residing in France, and (ii) that will result in the relevant investor acquiring the control of, all or part of a business of, or more than 25% (anticipated to be reduced to 10% for the biotech sector from July 1 to December 31, 2020) of the share capital or voting rights of, a company registered in France and developing activities in certain strategic industries, such as, energy, public health, biotech, telecommunications, artificial intelligence, cybersecurity, robotics, data collection or dual-use goods and technology is subject to the prior authorization by the French Ministry of Economy. In the absence of such authorization, the relevant investment shall be deemed null and void.

Assignment and Transfer of Shares. Shares are freely negotiable, subject to applicable legal and regulatory provisions (including, in particular, the prohibition on insider trading).

Listing

Our ADSs have been listed on the Nasdaq Global Market under the symbol “CLLS” and our ordinary shares have been listed on the Euronext Growth market of Euronext in Paris under the symbol “ALCLS”.

Transfer Agent and Registrar

The transfer agent and registrar for our ADSs is Citibank, N.A. The transfer agent and registrar for our ordinary shares is Société Générale Securities Services.

Differences in Corporate Law

The laws applicable to French sociétés anonymes differ from laws applicable to U.S. corporations and their shareholders. Set forth below is a summary of certain differences between the provisions of the French

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Commercial Code applicable to us and the Delaware General Corporation Law relating to shareholders’ rights and protections. This summary is not intended to be a complete discussion of the respective rights and it is qualified in its entirety by reference to Delaware law and French law.

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DESCRIPTION OF PREFERRED SHARES

The particular terms of each issue or series of preferred shares will be described in the related prospectus supplement. This description will include, where applicable, a description of:

Prior to issuing preferred shares, we must convene an extraordinary shareholders meeting at which shareholders would determine the terms and conditions of the preferred shares, decide the issuance of the preferred shares or delegate authority to the board of directors to decide the issuance and vote to modify the By-laws in order to include the characteristics and particular rights of the preferred shares.

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The extraordinary shareholders meeting would also decide the maximum aggregate amount of share capital increases which we may carry out by issuing preferred shares, which may not exceed a specified amount of gross issue proceeds to be determined.

When we issue preferred shares under this prospectus and the applicable prospectus supplement, the shares will be fully paid and non-assessable and, to the extent permitted under French law, will not have, or be subject to, any preemptive or similar rights.

The issuance of preferred shares could adversely affect the voting power of holders of ordinary shares and ADSs and reduce the likelihood that holders of ordinary shares and ADSs will receive dividend payments and payments upon liquidation. The issuance could have the effect of decreasing the market price of our ADSs. The issuance of preferred shares also could have the effect of delaying, deterring or preventing a change in control of our company.

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DESCRIPTION OF WARRANTS

We may issue warrants for the purchase of our preferred or ordinary shares or any combination of the foregoing. Each warrant will entitle the holder to purchase the number of preferred shares, ordinary shares, or combination thereof, as the case may be, at the exercise price and in the manner specified in the prospectus supplement relating to such warrants. Warrants may be exercised at any time up to the date and time specified in the applicable warrant agreement and set forth in the applicable prospectus supplement.

Warrants will be issued under one or more warrant agreements to be entered into between the Company and one or more purchasers of such warrants or a bank or trust company acting as warrant agent. The material terms and provisions of such warrants to be issued and a description of the material provisions of the applicable warrant agreement will be set forth in the applicable prospectus supplement. The form of warrant agreement that will be entered into with respect to a particular offering of warrants will be filed as an exhibit to a post-effective amendment to, or incorporated by reference into, the registration statement of which this prospectus forms a part.

The applicable prospectus supplement will describe the terms of any warrants in respect of which this prospectus and such prospectus supplement is being delivered, which terms may include the following if applicable to those warrants:

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DESCRIPTION OF AMERICAN DEPOSITARY SHARES

Citibank, N.A. has agreed to act as the depositary for the American Depositary Shares related to our ordinary shares. Citibank’s depositary offices are located at 388 Greenwich Street, New York, New York 10013. American Depositary Shares are frequently referred to as ADSs and represent ownership interests in securities that are on deposit with the depositary. ADSs may be represented by certificates that are commonly known as American Depositary Receipts or ADRs. The depositary typically appoints a custodian to safekeep the securities on deposit. In this case, the custodian is Citibank Europe plc, located at EGSP 186, 1 North Wall Quay, Dublin 1 Ireland.

We have appointed Citibank as depositary pursuant to a deposit agreement. A copy of the deposit agreement is on file with the SEC under cover of a registration statement on Form F-6. You may obtain a copy of the deposit agreement from the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549 and from the SEC’s website (www.sec.gov). Please refer to Registration Number 333-202488 when retrieving such copy.

We are providing you with a summary description of the material terms of the ADSs and of your material rights as an owner of ADSs. Please remember that summaries by their nature lack the precision of the information summarized and that the rights and obligations of an owner of ADSs will be determined by reference to the terms of the deposit agreement and not by this summary. We urge you to review the deposit agreement in its entirety.

Each ADS represents the right to receive, and to exercise the beneficial interests in one ordinary share that are on deposit with the depositary and/or custodian. An ADS also represents the right to receive, and to exercise the beneficial interests in, any other property received by the depositary bank or the custodian on behalf of the owner of the ADS but that has not been distributed to the owners of ADSs because of legal restrictions or practical considerations. The custodian, the depositary and their respective nominees will hold all deposited property for the benefit of the holders and beneficial owners of ADSs. The deposited property does not constitute the proprietary assets of the depositary, the custodian or their nominees. Beneficial ownership in the deposited property will under the terms of the deposit agreement be vested in the beneficial owners of the ADSs. The depositary, the custodian and their respective nominees will be the record holders of the deposited property represented by the ADSs for the benefit of the holders and beneficial owners of the corresponding ADSs. A beneficial owner of ADSs may or may not be the holder of such ADSs. Beneficial owners of ADSs will be able to receive, and to exercise beneficial ownership interests, in the deposited property only through the registered holders of the ADSs, the registered holders of the ADSs (on behalf of the applicable ADS owners) only through the depositary, and the depositary (on behalf of the owners of the corresponding ADSs) directly, or indirectly, through the custodian or their respective nominees, in each case upon the terms of the deposit agreement.

If you become an owner of ADSs, you will become a party to the deposit agreement and therefore will be bound to its terms and to the terms of any ADR that represents your ADSs. The deposit agreement and the ADR specify our rights and obligations as well as your rights and obligations as owner of ADSs and those of the depositary. As an ADS holder you appoint the depositary to act on your behalf in certain circumstances. The deposit agreement and the ADRs are governed by New York law. However, our obligations to the holders of ordinary shares will continue to be governed by the laws of France, which may be different from the laws in the United States.

In addition, applicable laws and regulations may require you to satisfy reporting requirements and obtain regulatory approvals in certain circumstances. You are solely responsible for complying with such reporting requirements and obtaining such approvals. Neither the depositary, the custodian, us nor any of their or our respective agents or affiliates shall be required to take any actions whatsoever on your behalf to satisfy such reporting requirements or obtain such regulatory approvals under applicable laws and regulations.

As an owner of ADSs, we will not treat you as one of our shareholders and you will not have direct shareholder rights. The depositary will hold on your behalf the shareholder rights attached to the ordinary shares

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underlying your ADSs. As an owner of ADSs you will be able to exercise the shareholders rights for the ordinary shares represented by your ADSs through the depositary only to the extent contemplated in the deposit agreement. To exercise any shareholder rights not contemplated in the deposit agreement you will, as an ADS owner, need to arrange for the cancellation of your ADSs and become a direct shareholder.

As an owner of ADSs, you may hold your ADSs either by means of an ADR registered in your name, through a brokerage or safekeeping account, or through an account established by the depositary in your name reflecting the registration of uncertificated ADSs directly on the books of the depositary, commonly referred to as the direct registration system, or DRS. The direct registration system reflects the uncertificated (book-entry) registration of ownership of ADSs by the depositary. Under the direct registration system, ownership of ADSs is evidenced by periodic statements issued by the depositary to the holders of the ADSs. The direct registration system includes automated transfers between the depositary and The Depository Trust Company, or DTC, the central book-entry clearing and settlement system for equity securities in the United States. If you decide to hold your ADSs through your brokerage or safekeeping account, you must rely on the procedures of your broker or bank to assert your rights as ADS owner. Banks and brokers typically hold securities such as the ADSs through clearing and settlement systems such as DTC. The procedures of such clearing and settlement systems may limit your ability to exercise your rights as an owner of ADSs. Please consult with your broker or bank if you have any questions concerning these limitations and procedures. All ADSs held through DTC will be registered in the name of a nominee of DTC. This summary description assumes you have opted to own the ADSs directly by means of an ADS registered in your name and, as such, we will refer to you as the “holder.” When we refer to “you,” we assume the reader owns ADSs and will own ADSs at the relevant time.

The registration of the ordinary shares in the name of the depositary or the custodian shall, to the maximum extent permitted by applicable law, vest in the depositary or the custodian the record ownership in the applicable ordinary shares with the beneficial ownership rights and interests in such ordinary share being at all times vested with the beneficial owners of the ADSs representing the ordinary shares. The depositary or the custodian shall at all times be entitled to exercise the beneficial ownership rights in all deposited property, in each case only on behalf of the holders and beneficial owners of the ADSs representing the deposited property.

Dividends and Distributions

As a holder of ADSs, you generally have the right to receive the distributions we make on the securities deposited with the custodian. Your receipt of these distributions may be limited, however, by practical considerations and legal limitations. Holders of ADSs will receive such distributions under the terms of the deposit agreement in proportion to the number of ADSs held as of a specified record date, after deduction of the applicable fees, taxes and expenses.

Distributions of Cash

Whenever we make a cash distribution for the securities on deposit with the custodian, we will deposit the funds with the custodian. Upon receipt of confirmation of the deposit of the requisite funds, the depositary will arrange for the funds to be converted into U.S. dollars and for the distribution of the U.S. dollars to the holders, subject to French laws and regulations.

The conversion into U.S. dollars will take place only if practicable and if the U.S. dollars are transferable to the United States. The depositary will apply the same method for distributing the proceeds of the sale of any property (such as undistributed rights) held by the custodian in respect of securities on deposit.

The distribution of cash will be made net of the fees, expenses, taxes and governmental charges payable by holders under the terms of the deposit agreement. The depositary will hold any cash amounts it is unable to distribute in a non-interest bearing account for the benefit of the applicable holders and beneficial owners of ADSs until the distribution can be effected or the funds that the depositary holds must be escheated as unclaimed property in accordance with the laws of the relevant states of the United States.

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Distributions of Shares

Whenever we make a free distribution of ordinary shares for the securities on deposit with the custodian, we will deposit the applicable number of ordinary shares with the custodian. Upon receipt of confirmation of such deposit, the depositary will either distribute to holders new ADSs representing the ordinary shares deposited or modify the ADS-to-ordinary share ratio, in which case each ADS you hold will represent rights and interests in the additional ordinary shares so deposited. Only whole new ADSs will be distributed; fractional entitlements will be sold and the proceeds of such sale will be distributed as in the case of a cash distribution.

The distribution of new ADSs or the modification of the ADS-to-ordinary share ratio upon a distribution of ordinary shares will be made net of the fees, expenses, taxes and governmental charges payable by holders under the terms of the deposit agreement. In order to pay such taxes or governmental charges, the depositary may sell all or a portion of the new ordinary shares so distributed.

No such distribution of new ADSs will be made if it would violate a law (e.g., the U.S. securities laws) or if it is not operationally practicable. If the depositary does not distribute new ADSs as described above, it may sell the ordinary shares received upon the terms described in the deposit agreement and will distribute the proceeds of the sale as in the case of a distribution of cash.

Distributions of Rights

Whenever we intend to distribute rights to purchase additional ordinary shares, we will give prior notice to the depositary and we will assist the depositary in determining whether it is lawful and practicable to distribute rights to purchase additional ADSs to holders.

The depositary will establish procedures to distribute rights to purchase additional ADSs to holders and to enable such holders to exercise such rights if it is lawful and practicable to make the rights available to holders of ADSs, and if we provide all of the documentation contemplated in the deposit agreement (such as opinions to address the lawfulness of the transaction). You may have to pay fees, expenses, taxes and other governmental charges to subscribe for the new ADSs upon the exercise of your rights. The depositary is not obligated to establish procedures to facilitate the distribution and exercise by holders of rights to purchase new ordinary shares other than in the form of ADSs.

The depositary will not distribute the rights to you if:

The depositary will sell the rights that are not exercised or not distributed if such sale is lawful and practicable. The proceeds of such sale will be distributed to holders as in the case of a cash distribution. If the depositary is unable to sell the rights, it will allow the rights to lapse.

Elective Distributions

Whenever we intend to distribute a dividend payable at the election of shareholders either in cash or in additional shares, we will give prior notice thereof to the depositary and will indicate whether we wish the elective distribution to be made available to you. In such case, we will assist the depositary in determining whether such distribution is lawful and practicable.

The depositary will make the election available to you only if it is practicable and if we have provided all of the documentation contemplated in the deposit agreement. In such case, the depositary will establish procedures to enable you to elect to receive either cash or additional ADSs, in each case as described in the deposit agreement.

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If the election is not made available to you, you will receive either cash or additional ADSs, depending on what a shareholder in France would receive upon failing to make an election, as more fully described in the deposit agreement.

Other Distributions

Whenever we intend to distribute property other than cash, ordinary shares or rights to purchase additional ordinary shares, we will notify the depositary in advance and will indicate whether we wish such distribution to be made to you. If so, we will assist the depositary in determining whether such distribution to holders is lawful and practicable.

If it is practicable to distribute such property to you and if we provide all of the documentation contemplated in the deposit agreement, the depositary will distribute the property to the holders in a manner it deems practicable.

The distribution will be made net of fees, expenses, taxes and governmental charges payable by holders under the terms of the deposit agreement. In order to pay such taxes and governmental charges, the depositary bank may sell all or a portion of the property received.

The depositary will not distribute the property to you and will sell the property if:

The proceeds of such a sale will be distributed to holders as in the case of a cash distribution.

Redemption

Whenever we decide to redeem any of the securities on deposit with the custodian, we will notify the depositary in advance. If it is practicable and if we provide all of the documentation contemplated in the deposit agreement, the depositary will provide notice of the redemption to the holders.

The custodian will be instructed to surrender the shares being redeemed against payment of the applicable redemption price. The depositary will convert the redemption funds received into U.S. dollars upon the terms of the deposit agreement and will establish procedures to enable holders to receive the net proceeds from the redemption upon surrender of their ADSs to the depositary. You may have to pay fees, expenses, taxes and other governmental charges upon the redemption of your ADSs. If less than all ADSs are being redeemed, the ADSs to be retired will be selected by lot or on a pro rata basis, as the depositary may determine.

Changes Affecting Ordinary Shares

The ordinary shares held on deposit for your ADSs may change from time to time. For example, there may be a change in nominal or par value, a split-up, cancellation, consolidation or reclassification of such ordinary shares or a recapitalization, reorganization, merger, consolidation or sale of assets.

If any such change were to occur, your ADSs would, to the extent permitted by law, represent the right to receive the property received or exchanged in respect of the ordinary shares held on deposit. The depositary may

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in such circumstances deliver new ADSs to you, amend the deposit agreement, the ADRs and the applicable registration statement(s) on Form F-6, call for the exchange of your existing ADRs for new ADRs and take any other actions that are appropriate to reflect as to the ADSs the change affecting the ordinary shares held in deposit for your ADSs. If the depositary bank may not lawfully distribute such property to you, the depositary may sell such property and distribute the net proceeds to you as in the case of a cash distribution.

Issuance of ADSs upon Deposit of Ordinary Shares

Upon completion of an offering, the ordinary shares being offered pursuant to this prospectus in such offering will be deposited by us with the custodian. Upon receipt of confirmation of such deposit, the depositary will issue ADSs to the applicable underwriters, dealer or other purchaser.

The depositary may create ADSs on your behalf if you or your broker deposit ordinary shares with the custodian. The depositary will deliver these ADSs to the person you indicate only after you pay any applicable issuance fees and any charges and taxes payable for the transfer of the ordinary shares to the custodian. Your ability to deposit ordinary shares and receive ADSs may be limited by U.S. and French legal considerations applicable at the time of deposit.

The issuance of ADSs may be delayed until the depositary or the custodian receives confirmation that all required approvals have been given and that the ordinary shares have been duly transferred to the custodian.

The depositary will only issue ADSs in whole numbers.

When you make a deposit of ordinary shares, you will be responsible for transferring good and valid title to the depositary. As such, you will be deemed to represent and warrant that:

If any of the representations or warranties are incorrect in any way, we and the depositary may, at your cost and expense, take any and all actions necessary to correct the consequences of the misrepresentations.

Transfer, Combination and Split Up of ADRs

As an ADR holder, you will be entitled to transfer, combine or split up your ADRs and the ADSs evidenced thereby. For transfers of ADRs, you will have to surrender the ADRs to be transferred to the depositary and also must:

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To have your ADRs either combined or split up, you must surrender the ADRs in question to the depositary with your request to have them combined or split up, and you must pay all applicable fees, charges and expenses payable by ADR holders, pursuant to the terms of the deposit agreement, upon a combination or split up of ADRs.

Withdrawal of Ordinary Shares Upon Cancellation of ADSs

As a holder, you will be entitled to present your ADSs to the depositary for cancellation and then receive the corresponding number of underlying ordinary shares at the custodian’s offices. Your ability to withdraw the ordinary shares held in respect of the ADSs may be limited by U.S. and French legal considerations applicable at the time of withdrawal. In order to withdraw the ordinary shares represented by your ADSs, you will be required to pay to the depositary the fees for cancellation of ADSs and any charges and taxes payable upon the transfer of the ordinary shares being withdrawn. You assume the risk for delivery of all funds and securities upon withdrawal. Once canceled, the ADSs will not have any rights under the deposit agreement.

If you hold ADSs registered in your name, the depositary may ask you to provide proof of identity and genuineness of any signature and such other documents as the depositary may deem appropriate before it will cancel your ADSs. The withdrawal of the ordinary shares represented by your ADSs may be delayed until the depositary receives satisfactory evidence of compliance with all applicable laws and regulations. Please keep in mind that the depositary will only accept ADSs for cancellation that represent a whole number of securities on deposit.

You will have the right to withdraw the securities represented by your ADSs at any time except for:

The deposit agreement may not be modified to impair your right to withdraw the securities represented by your ADSs except to comply with mandatory provisions of law.

Voting Rights

As a holder, you generally have the right under the deposit agreement to instruct the depositary to exercise the voting rights for the ordinary shares represented by your ADSs. The voting rights of holders of ordinary shares are described in the sections of this prospectus titled “Description of Share Capital” and “Limitations Affecting Shareholders of a French Company.”

At our request, the depositary will distribute to you any notice of shareholders’ meeting received from us together with information explaining how to instruct the depositary to exercise the voting rights of the securities represented by ADSs.

If the depositary timely receives voting instructions from a holder of ADSs, it will endeavor to vote the securities (in person or by proxy) represented by the holder’s ADSs in accordance with such voting instructions.

Please note that the ability of the depositary to carry out voting instructions may be limited by practical and legal limitations and the terms of the securities on deposit. We cannot assure you that you will receive voting materials in time to enable you to return voting instructions to the depositary in a timely manner.

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If the depositary receives voting instructions from a holder of ADSs that fail to specify the manner in which the depositary is to vote, the depositary will deem such holder (unless otherwise specified in the notice distributed to holders) to have instructed the depositary to vote in favor of all resolutions endorsed by our board of directors. With respect to securities represented by ADSs for which no timely voting instructions are received by the depositary from the holder, the depositary will (unless otherwise specified in the notice distributed to holders) deem such holder to have instructed the depositary to give a discretionary proxy to a person designated by us to vote the securities. However, no such discretionary proxy will be given by the depositary with respect to any matter to be voted upon as to which we inform the depositary that we do not wish such proxy to be given, substantial opposition exists, or the rights of holders of securities may be materially adversely affected.

Fees and Charges

As an ADS holder, you will be required to pay the following fees under the terms of the depositary agreement:

As an ADS holder you will also be responsible to pay certain fees and expenses incurred by the depositary and certain taxes and governmental charges such as:

ADS fees and charges payable upon (1) deposit of ordinary shares against issuance of ADSs and (2) surrender of ADSs for cancellation and withdrawal of ordinary shares are charged to the person to whom the

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ADSs are delivered (in the case of ADS issuances) and to the person who delivers the ADS, for cancellation (in the case of ADS cancellations). In the case of ADSs issued by the depositary into DTC or presented to the depositary via DTC, the ADS issuance and cancellation fees and charges may be deducted from distributions made through DTC, and may be charged to the DTC participant(s) receiving the ADSs or the DTC participant(s) surrendering the ADSs for cancellation, as the case may be, on behalf of the beneficial owner(s) and will be charged by the DTC participant(s) to the account(s) of the applicable beneficial owner(s) in accordance with the procedures and practices of the DTC participant(s) as in effect at the time. ADS fees and charges in respect of distributions and the ADS service fee are charged to the holders as of the applicable ADS record date. In the case of distributions of cash, the amount of the applicable ADS fees and charges is deducted from the funds being distributed. In the case of (1) distributions other than cash and (2) the ADS service fee, holders as of the ADS record date will be invoiced for the amount of the ADS fees and charges and such ADS fees and charges may be deducted from distributions made to holders of ADSs. For ADSs held through DTC, the ADS fees and charges for distributions other than cash and the ADS service fee may be deducted from distributions made through DTC, and may be charged to the DTC participants in accordance with the procedures and practices prescribed by DTC and the DTC participants in turn charge the amount of such ADS fees and charges to the beneficial owners for whom they hold ADSs.

In the event of refusal to pay the depositary fees, the depositary may, under the terms of the deposit agreement, refuse the requested service until payment is received or may set off the amount of the depositary fees from any distribution to be made to the ADS holder. Certain ADS fees and charges (such as the ADS service fee) may become payable shortly after the closing of the ADS offering.

Note that the fees and charges you may be required to pay may vary over time and may be changed by us and by the depositary. You will receive prior notice of such changes. The depositary may reimburse us for certain expenses incurred by us in respect of the ADR program, by making available a portion of the ADS fees charged in respect of the ADR program or otherwise, upon such terms and conditions as we and the depositary agree from time to time.

Amendments and Termination

We may agree with the depositary to modify the deposit agreement at any time without your consent. We undertake to give holders 30 days’ prior notice of any modifications that would materially prejudice any of their substantial rights under the deposit agreement. We will not consider to be materially prejudicial to your substantial rights any modifications or supplements that are reasonably necessary for the ADSs to be registered under the Securities Act or to be eligible for book-entry settlement, in each case without imposing or increasing the fees and charges you are required to pay. In addition, we may not be able to provide you with prior notice of any modifications or supplements that are required to accommodate compliance with applicable provisions of law.

You will be bound by the modifications to the deposit agreement if you continue to hold your ADSs after the modifications to the deposit agreement become effective. The deposit agreement cannot be amended to prevent you from withdrawing the ordinary shares represented by your ADSs (except as permitted by law).

We have the right to direct the depositary to terminate the deposit agreement. Similarly, the depositary may in certain circumstances on its own initiative terminate the deposit agreement. In either case, the depositary must give notice to the holders at least 30 days before termination. Until termination, your rights under the deposit agreement will be unaffected.

After termination, the depositary will continue to collect distributions received (but will not distribute any such property until you request the cancellation of your ADSs) and may sell the securities held on deposit. After the sale, the depositary will hold the proceeds from such sale and any other funds then held for the holders of

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ADSs in a non-interest bearing account. At that point, the depositary will have no further obligations to holders other than to account for the funds then held for the holders of ADSs still outstanding (after deduction of applicable fees, taxes and expenses).

Books of Depositary

The depositary will maintain ADS holder records at its depositary office. You may inspect such records at such office during regular business hours but solely for the purpose of communicating with other holders in the interest of business matters relating to the ADSs and the deposit agreement.

The depositary will maintain in New York facilities to record and process the issuance, cancellation, combination, split-up and transfer of ADSs. These facilities may be closed from time to time, to the extent not prohibited by law.

Limitations on Obligations and Liabilities

The deposit agreement limits our obligations and the depositary’s obligations to you. Please note the following:

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Pre-Release Transactions

Subject to the terms and conditions of the deposit agreement, the depositary may issue to broker/dealers ADSs before receiving a deposit of ordinary shares or release ordinary shares to broker/dealers before receiving ADSs for cancellation. These transactions are commonly referred to as “pre-release transactions,” and are entered into between the depositary and the applicable broker/dealer. The deposit agreement limits the aggregate size of pre-release transactions (not to exceed 30% of the ordinary shares on deposit in the aggregate) and imposes a number of conditions on such transactions (e.g., the need to receive collateral, the type of collateral required and the representations required from brokers). The depositary may retain the compensation received from the pre-release transactions.

Taxes

You will be responsible for the taxes and other governmental charges payable on the ADSs and the securities represented by the ADSs. We, the depositary and the custodian may deduct from any distribution the taxes and governmental charges payable by holders and may sell any and all property on deposit to pay the taxes and governmental charges payable by holders. You will be liable for any deficiency if the sale proceeds do not cover the taxes that are due.

The depositary may refuse to issue ADSs, to deliver, transfer, split and combine ADRs or to release securities on deposit until all taxes and charges are paid by the applicable holder. The depositary and the custodian may take reasonable administrative actions to obtain tax refunds and reduced tax withholding for any distributions on your behalf. However, you may be required to provide to the depositary and to the custodian proof of taxpayer status and residence and such other information as the depositary and the custodian may require to fulfill legal obligations. You are required to indemnify us, the depositary and the custodian for any claims with respect to taxes based on any tax benefit obtained for you.

Foreign Currency Conversion

The depositary will arrange for the conversion of all foreign currency received into U.S. dollars if such conversion is practical, and it will distribute the U.S. dollars in accordance with the terms of the deposit agreement. You may have to pay fees and expenses incurred in converting foreign currency, such as fees and expenses incurred in complying with currency exchange controls and other governmental requirements.

If the conversion of foreign currency is not practical or lawful, or if any required approvals are denied or not obtainable at a reasonable cost or within a reasonable period, the depositary may take the following actions in its discretion:

Governing Law/Waiver of Jury Trial

The deposit agreement and the ADRs will be interpreted in accordance with the laws of the State of New York. The rights of holders of ordinary shares (including ordinary shares represented by ADSs) are governed by the laws of France.

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LIMITATIONS AFFECTING SHAREHOLDERS OF A FRENCH COMPANY

Ownership of ADSs or Shares by Non-French Residents

Neither the French Commercial Code nor our By-laws presently impose any restrictions on the right of non-French residents or non-French shareholders to own and vote shares.

However, non-French residents must file a declaration for statistical purposes with the Bank of France (Banque de France) within twenty working days following the date of certain direct foreign investments in us, including any purchase of our ADSs. In particular, such filings are required in connection with investments exceeding €15,000,000 that lead to the acquisition of at least 10% of our Company’s share capital or voting rights or cross such 10% threshold. Violation of this filing requirement may be sanctioned by five years of imprisonment and a fine of up to twice the amount of the relevant investment. This amount may be increased fivefold if the violation is made by a legal entity.

Further, any investment (i) by an individual or entity located in a country that is not a member State of the European Union or of a member State of the European Economic Area having entered into a convention on administrative assistance against tax evasion and fraud with France, or by a French citizen not residing in France, and (ii) that will result in the relevant investor acquiring the control of, all or part of a business of, or more than 25% (anticipated to be reduced to 10% for the biotech sector from July 1 to December 31, 2020) of the share capital or voting rights of, a company registered in France and developing activities in certain strategic industries, such as, energy, public health, biotech telecommunications, artificial intelligence, cybersecurity, robotics, data collection or dual-use goods and technology is subject to the prior authorization by the French Ministry of Economy. In the absence of such authorization, the relevant investment shall be deemed null and void.

Foreign Exchange Controls

Under current French foreign exchange control regulations there are no limitations on the amount of cash payments that we may remit to residents of foreign countries. Laws and regulations concerning foreign exchange controls do, however, require that all payments or transfers of funds made by a French resident to a non-resident such as dividend payments be handled by an accredited intermediary. All registered banks and substantially all credit institutions in France are accredited intermediaries.

Availability of Preferential Subscription Rights

In accordance with French law, our shareholders have preferential subscription rights to subscribe for new shares or other securities giving rights to acquire additional shares immediately or in the future on a pro rata basis, as described under the section of this prospectus titled “Description of Share Capital—Key Provisions of Our By-laws and French Law Affecting Our Ordinary Shares—Changes in Share Capital—Preferential Subscription Right (Preemptive Rights).”

Holders of our securities in the U.S. (which may be in the form of shares or ADSs) may not be able to exercise preferential subscription rights for their securities unless a registration statement under the Securities Act is effective with respect to such rights or an exemption from the registration requirements imposed by the Securities Act is available. We may, from time to time, issue new shares or other securities giving rights to acquire additional shares (such as warrants) at a time when no registration statement is in effect and no Securities Act exemption is available. If so, holders of our securities in the U.S. will be unable to exercise any preferential subscription rights and their interests will be diluted. We are under no obligation to file any registration statement in connection with any issuance of new shares or other securities. We intend to evaluate at the time of any rights offering the costs and potential liabilities associated with registering the rights, as well as the indirect benefits to us of enabling the exercise by holders of shares and holders of ADSs in the U.S. of the subscription rights, and any other factors we consider appropriate at the time, and then to make a decision as to whether to register the rights. We cannot assure you that we will file a registration statement.

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For holders of our ordinary shares in the form of ADSs, the depositary may make these rights or other distributions available to ADS holders. If the depositary does not make the rights available to ADS holders and determines that it is impractical to sell the rights, it may allow these rights to lapse. In that case the holders will receive no value for them. The section of this prospectus titled “Description of American Depositary Shares—Dividends and Distributions” explains in detail the depositary’s responsibility in connection with a rights offering.

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PLAN OF DISTRIBUTION

We may sell or otherwise offer our securities described herein:

The distribution of securities may be carried out, from time to time, in one or more transactions, including:

The prospectus supplement with respect to a particular offering will set forth the terms of the offering, including the following:

Underwriters may offer and sell the securities at a fixed price or prices, which may be changed, or from time to time at market prices prevailing at the time of sale, at prices related to prevailing market prices or at negotiated prices. We may, from time to time, authorize agents acting on a best or reasonable efforts basis as our agents to solicit or receive offers to purchase the securities upon the terms and conditions as are set forth in the applicable prospectus supplement. In connection with the sale of securities, underwriters or agents may be deemed to have received compensation from us in the form of underwriting discounts or commissions and may also receive commissions from purchasers of securities for whom they may act as agent. Underwriters may sell securities to or through dealers, and dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or commissions from the purchasers for whom they may act as agent.

Underwriters, dealers and agents who participate in the distribution of securities and their controlling persons may be entitled, under agreements that may be entered into with us to indemnification by us against certain liabilities, including liabilities under the Securities Act, or to contribution with respect to payments that the underwriters, dealers or agents and their controlling persons may be required to make in respect of those liabilities.

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We may also make direct sales through subscription rights distributed to our existing shareholders on a pro rata basis, which may or may not be transferable. In any distribution of subscription rights to our shareholders, if all of the underlying securities are not subscribed for, we may then sell the unsubscribed securities directly to third parties or may engage the services of one or more underwriters, dealers or agents, including standby underwriters, to sell the unsubscribed securities to third parties.

Some of the securities that we offer through this prospectus may be new issues of securities with no established trading market. Any underwriters to whom we sell our securities for public offering and sale may make a market in those securities, but they will not be obligated to do so and they may discontinue any market making at any time without notice. Accordingly, we cannot assure you of the liquidity of, or continued trading markets for, any securities that we offer.

Certain persons participating in an offering may engage in over-allotment, stabilizing transactions, short-covering transactions and penalty bids in accordance with Regulation M under the Exchange Act that stabilize, maintain or otherwise affect the price of the offered securities. If any such activities will occur, they will be described in the applicable prospectus supplement.

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ENFORCEABILITY OF CIVIL LIABILITIES

We are a société anonyme, or S.A., organized under the laws of France. The majority of our directors and officers are citizens and residents of countries other than the United States, and the majority of our assets are located outside of the United States. Accordingly, U.S. investors may find it difficult and may be unable:

We have been informed by Jones Day, our counsel, that there is doubt as to enforceability in France, either in original actions or in actions for enforcement of judgments of U.S. courts, of civil liabilities predicated in the U.S. federal securities laws.

In addition, actions in the United States under the U.S. federal securities laws could be affected under certain circumstances by the French law No. 68-678 of July 26, 1968 as amended by French Law No. 80-538 of July 16, 1980, which may preclude or restrict the obtaining of evidence in France or from French persons in connection with those actions. Each of the foregoing statements also applies to our auditors.

WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form F-3 under the Securities Act with respect to the securities described in this prospectus. This prospectus does not contain all of the information set forth in the registration statement that we filed. In addition, we are subject to the informational and periodic reporting requirements of the Exchange Act applicable to foreign private issuers and fulfill the obligations with respect to those requirements by filing reports with the SEC. You may read and copy any document that we file with the SEC at the SEC’s Public Reference Room at 100 F. Street, N.E., Washington, D.C. 20549. Copies of such materials are also available by mail from the Public Reference Branch of the SEC at prescribed rates. In addition, our SEC filings are available to the public at the SEC’s web site at http://www.sec.gov. You may obtain further information by calling the SEC at 1-800-SEC-0330 or by logging on to the SEC’s website.

Our ordinary shares are listed on the Euronext Growth market of Euronext in Paris and on the Nasdaq Global Market, the latter in the form of ADSs. You can consult reports and other information about us that are filed pursuant to the rules of the Euronext Growth market of Euronext in Paris and of the Nasdaq Global Market at these exchanges.

You may request a copy of this prospectus, any of the information that is incorporated by reference in this prospectus and any document summarized in this prospectus, without charge, upon written or oral request. If you would like to obtain this information from us, please direct your request, either in writing or by telephone, to:

Investor Relations

Cellectis S.A.

8 rue de law Croix Jarry

75013 Paris, France

+33 1 81 69 16 00

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INCORPORATION OF INFORMATION BY REFERENCE

The SEC allows us to “incorporate by reference” into this prospectus and any accompanying prospectus supplement the information we have filed with the SEC. This means that we can disclose important information by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be a part of this prospectus, and information that we file later with the SEC will also be deemed to be incorporated by reference into this prospectus and to be a part hereof from the date of filing of such documents and will automatically update and supersede previously filed information, including information contained in this document.

We incorporate by reference into this prospectus and any accompanying prospectus supplement the following documents:

We are also incorporating by reference all subsequent annual reports on Form 20-F that we file with the SEC and those of our reports on Form 6-K that we furnish to the SEC that we specifically identify in such form or in the applicable prospectus supplement as being incorporated by reference into this prospectus or such prospectus supplement after the date hereof and prior to the completion of an offering of securities under this prospectus.

Any statement made in this prospectus concerning the contents of any contract, agreement or other document is only a summary of the actual document. Each statement regarding a contract, agreement or other document is qualified in its entirety by reference to the actual document.

LEGAL MATTERS

Unless otherwise indicated in the applicable prospectus supplement, the validity of the ordinary shares represented by the ADSs, the preferred shares and the warrants and certain legal matters relating to French law will be passed upon by Jones Day, Paris, France, and the validity of the warrants and certain legal matters relating to U.S. federal and New York law will be passed upon by Jones Day, New York, New York.

EXPERTS

The consolidated financial statements of Cellectis appearing in Cellectis’ Annual Report (Form 20-F) for the year ended December 31, 2019 and the effectiveness of Cellectis’ internal control over financial reporting as of December 31, 2019 have been audited by Ernst & Young et Autres, independent registered public accounting firm, as set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

The offices of Ernst & Young et Autres are located at Tour First, 1 place des Saisons, 92037 Paris—La Défense Cedex, France.

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Ordinary Shares

Preferred Shares

Warrants

PROSPECTUS

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PART II. INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 8. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

Under French law, provisions of By-laws that limit the liability of directors and officers are prohibited. However, French law allows sociétés anonymes to contract for and maintain liability insurance against civil liabilities incurred by any of their directors and officers involved in a third-party action, provided that they acted in good faith and within their capacities as directors or officers of the company. Criminal liability cannot be indemnified under French law, whether directly by the company or through liability insurance.

We maintain liability insurance for our directors and officers, including insurance against liability under the Securities Act of 1933, as amended.

Certain of our non-employee directors may, through their relationships with their employers or partnerships, be insured and/or indemnified against certain liabilities in their capacity as members of our board of directors.

In any underwriting agreement we enter into in connection with the sale of securities being registered hereby, the underwriters will agree to indemnify, under certain conditions, us, our directors, our officers and persons who control us within the meaning of the Securities Act against certain liabilities.

ITEM 9. EXHIBITS.

The following exhibits are filed herewith or incorporated by reference herein:

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ITEM 10. UNDERTAKINGS.

Provided, however, that:

paragraphs (a)(1)(i), (a)(1)(ii) and (a)(1)(iii) of this section do not apply if the registration statement is on Form F-3 and the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the registrant pursuant to section 13 or section 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

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EXHIBIT INDEX

The following exhibits are filed herewith or incorporated by reference herein:

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SIGNATURES

Pursuant to the requirements of the Securities Act, the Registrant certifies that it has reasonable grounds to believe it meets all of the requirements for filing on Form F-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in Paris, France, on June 2, 2020.

POWER OF ATTORNEY

We, the undersigned directors, officers and / or authorized representative in the United States of Cellectis S.A., hereby severally constitute and appoint Dr. André Choulika and Marie-Bleuenn Terrier, and each of them singly, our true and lawful attorneys-in-fact and agents, with full power to any of them, and to each of them singly, to sign for us and in our names in the capacities indicated below any and all amendments (including post-effective amendments) to this registration statement, and to any related registration statement filed pursuant to Rule 462(b) under the Securities Act of 1933, as amended, in connection with the registration under the Securities Act of 1933, as amended, of securities of Cellectis, and to file or cause to be filed the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorneys-in-fact, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully to all intents and purposes as each of them might or could do in person, and hereby ratifying and confirming all that said attorneys, and each of them, or their substitute or substitutes, shall do or cause to be done by virtue of this Power of Attorney.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities indicated on June 2, 2020.

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Exhibit 5.1

[JONES DAY LETTERHEAD]

June 2, 2020

Cellectis S.A.

8, rue de la Croix Jarry

75013 Paris, France

Re: Registration Statement on Form F-3 filed by Cellectis S.A.

Ladies and Gentlemen:

We are acting as special French counsel for Cellectis S.A., a French société anonyme (the “Company”) in connection with the authorization of the possible issuance and sale from time to time, on a delayed basis, by the Company of an indeterminate amount of (i) ordinary shares of the Company (the “Ordinary Shares”); (ii) preferred shares of the Company (the “Preferred Shares”); or (iii) warrants to purchase Ordinary Shares and/or Preferred Shares (the “Warrants”, and together with the Ordinary Shares and the Preferred Shares, the “Securities”) in each case as contemplated by the Registration Statement on Form F-3 as filed by the Company with the United States Securities and Exchange Commission (the “Commission”) to which this opinion is filed as an exhibit (as the same may be amended from time to time, the “Registration Statement”). The Securities may be offered and sold from time to time pursuant to Rule 415 under the Securities Act of 1933 (the “Securities Act”).

In connection with the opinions expressed herein, we have examined such documents, records and matters of law as we have deemed relevant or necessary for purposes of such opinions. Based on the foregoing, and subject to the further limitations, qualifications and assumptions set forth herein, we are of the opinion that:

1.    The Ordinary Shares, when (a) the extraordinary shareholders’ meeting of the Company and, as the case may be, the Board of Directors of the Company (the “Board”), and/or the meeting of any holders of a specific category of securities of the Company, have taken all necessary corporate action to approve the issuance of, and establish the terms of, the offering of the Ordinary Shares and related matters, and (b) issued, sold and delivered in the manner and for the consideration stated in the applicable definitive purchase, underwriting, placement or similar agreement approved by the Board, as the case may be, upon payment of the consideration provided therein to the Company, will be validly issued, fully paid and non-assessable.

2.     The Preferred Shares, when (a) the extraordinary shareholders’ meeting of the Company and, as the case may be, the Board and/or the meeting of any holders of a specific category of securities of the Company, have taken all necessary corporate action to authorize and approve the issuance of, and establish the terms of, the offering of Preferred Shares and related matters, and (b) issued, sold and delivered in the manner and for the consideration stated in the applicable definitive purchase, underwriting, placement or similar agreement approved by the Board, as the case may be, upon payment of the consideration provided therein to the Company, will be validly issued, fully paid and non-assessable.

3.     The Warrants, when (a) the extraordinary shareholders’ meeting of the Company and, as the case may be, the Board and/or the meeting of any holders of a specific category of securities of the Company, have taken all necessary corporate action to approve the issuance of and establish the terms of such Warrants, the terms of the offering of the Warrants and related matters, and (b) issued, sold and delivered in the manner and for the consideration stated in the applicable definitive purchase, underwriting, placement or similar agreement approved by the Board as the case may be, and upon payment of the consideration approved by the Board, the Warrants will be validly issued.

In rendering the foregoing opinion, we have assumed that (i) the Registration Statement, and any amendments thereto, will have become effective under the Securities Act (and will remain effective at the time of issuance of any Securities thereunder); (ii) a prospectus supplement describing each class and/or series of Securities offered pursuant to the Registration Statement, to the extent required by applicable law and the relevant rules and regulations of the Commission will be timely filed with the Commission; (iii) the resolutions authorizing the Company to issue, offer and sell the Securities as adopted by the extraordinary shareholders’ meeting and/or the Board, as applicable, will be in full force and effect at all times at which the Securities are issued, offered or sold by the Company; (iv) the definitive terms of the Securities will have been established in accordance with the authorizing resolutions adopted by the extraordinary shareholders’ meeting and/or the Board, as applicable, the Company’s By-laws and applicable law; (v) the Company will issue and deliver the Securities in the manner contemplated in the Registration Statement and the amount of Securities issued will remain within the limits of the then authorized but unissued amounts of such Securities; (vi) all Securities will be issued in compliance with applicable securities and corporate law; and (vii) any deposit agreement, warrant agreement, purchase contract agreement or similar agreement will constitute a valid and binding obligation of each party thereto other than the Company.

As to facts material to the opinions and assumptions expressed herein, we have relied upon written statements and representations of officers and other representatives of the Company. We are members of the Paris bar and this opinion is limited to the laws of the Republic of France. This opinion is subject to the sovereign power of the French courts to interpret the facts and circumstances of any adjudication. This opinion is given on the basis that it is to be governed by, and construed in accordance with, the laws of the Republic of France.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference to Jones Day under the caption “Legal Matters” in the prospectus constituting a part of such Registration Statement. In giving such consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Exhibit 5.2

[JONES DAY LETTERHEAD]

June 2, 2020

Cellectis S.A.

8, rue de la Croix Jarry

75013 Paris, France

Re: Registration Statement on Form F-3 Filed by Cellectis S.A.

Ladies and Gentlemen:

We have acted as special United States counsel for Cellectis S.A., a French société anonyme (the “Company”), in connection with the authorization of the possible issuance and sale from time to time, on a delayed basis, by the Company of an indeterminate amount of warrants to purchase ordinary shares of the Company and/or preferred shares of the Company (the “Warrants”) as contemplated by the Registration Statement on Form F-3 as filed by the Company with the United States Securities and Exchange Commission (the “Commission”), to which this opinion is filed as an exhibit (as the same may be amended from time to time, the “Registration Statement”). The Warrants may be offered and sold from time to time pursuant to Rule 415 under the Securities Act of 1933 (the “Securities Act”).

In connection with the opinion expressed herein, we have examined such documents, records and matters of law as we have deemed relevant or necessary for purposes of such opinion. Based on the foregoing, and subject to the further limitations, qualifications and assumptions set forth herein, we are of the opinion that the Warrants, upon receipt by the Company of such lawful consideration therefore as the Company’s Board of Directors (or an authorized committee thereof) may determine, will constitute valid and binding obligations of the Company.

In rendering the foregoing opinion, we have assumed that: (i) the Registration Statement, and any amendments thereto, will have become effective under the Securities Act (and will remain effective at the time of issuance of any Warrants thereunder); (ii) a prospectus supplement describing the terms of the Warrants offered pursuant to the Registration Statement, to the extent required by applicable law and the relevant rules and regulations of the Commission, will be timely filed with the Commission; (iii) the resolutions authorizing the Company to issue, offer and sell the Warrants will have been adopted by the Board of Directors (or an authorized committee thereof) and/or the shareholders of the Company, as applicable, and will be in full force and effect at all times at which the Warrants are offered and sold by the Company; (iv) the definitive terms of the Warrants will have been established in accordance with all requisite corporate action and applicable law, including French law; (v) the Company will issue and deliver the Warrants in the manner contemplated by the Registration Statement; (vi) all Warrants will be issued in compliance with applicable federal and state securities laws; and (vii) any Warrant Agreement (defined below) will be governed, in whole or in part by, and construed in accordance with, the laws of the State of New York and will constitute a valid and binding obligation of each party thereto other than the Company.

We have further assumed that (i) the warrant agreement, approved by us, relating to the Warrants (the “Warrant Agreement”) to be entered into between the Company and an entity selected by the Company to act as the warrant agent (the “Counterparty”) will have been authorized, executed and delivered by the Company and the Counterparty, and (ii) the Warrants will be authorized, executed and delivered by the Company and the Counterparty in accordance with the provisions of the Warrant Agreement.

We have further assumed that (a) the Company is and will be a French société anonyme existing and in good standing under the laws of France, (b) the Warrant Agreement and the underlying ordinary and/or preferred shares have been or will have been (i) authorized by all necessary corporate action of the Company and (ii) executed and delivered by the Company under the laws of France, (c) the choice of New York law to govern, in whole or in part, the Warrant Agreement and any choice of New York forum provisions included in the Warrant Agreement are valid choices under the laws of France, (d) the execution, delivery, performance and compliance with the terms and provisions of the Warrant Agreement by the Company do not and will not violate or conflict with the laws of France or the terms and provisions of the Company’s By-laws (including any amendments thereto), or any rule, regulation, order, decree, judgment, instrument or agreement binding upon or applicable to the Company or its properties.

The opinion expressed herein is limited by bankruptcy, insolvency, reorganization, fraudulent transfer and fraudulent conveyance, voidable preference, moratorium or other similar laws and related regulations and judicial doctrines from time to time in effect relating to or affecting creditors’ rights generally, and by general equitable principles and public policy considerations, whether such principles and considerations are considered in a proceeding at law or at equity.

As to facts material to the opinion and assumptions expressed herein, we have relied upon oral or written statements of representations of officers and other representatives of the Company.

The opinion expressed herein is limited to the laws of the State of New York, as currently in effect, and we express no opinion as to the effect of the laws of any other jurisdiction, including in particular the laws of France.

We hereby consent to the filing of this opinion as Exhibit 5.2 to the Registration Statement and to the reference to Jones Day under the caption “Legal Matters” in the prospectus constituting a part of such Registration Statement. In giving such consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the reference to our firm under the caption “Experts” in the Registration Statement (Form F-3) and related Prospectus of Cellectis S.A. for the registration of an indeterminate number of ordinary shares, preferred shares and warrants, and to the incorporation by reference therein of our reports dated March 4, 2020, with respect to the consolidated financial statements of Cellectis S.A. and the effectiveness of internal control over financial reporting of Cellectis S.A., included in its Annual Report (Form 20-F) for the year ended December 31, 2019, filed with the Securities and Exchange Commission.