Exhibit 1.1

Execution Version

5,434,783 Shares

SYNDAX PHARMACEUTICALS, INC.

COMMON STOCK (PAR VALUE $0.0001 PER SHARE)

UNDERWRITING AGREEMENT

December 8, 2020

December 8, 2020

Goldman Sachs & Co. LLC

Citigroup Global Markets Inc.

Cowen and Company, LLC

c/o Goldman Sachs & Co. LLC

200 West Street

New York, New York 10282-2198

c/o Citigroup Global Markets Inc.

388 Greenwich Street

New York, New York 10013

c/o Cowen and Company, LLC

599 Lexington Avenue

New York, New York 10022

Ladies and Gentlemen:

Syndax Pharmaceuticals, Inc., a Delaware corporation (the “Company”), proposes to issue and sell to the several Underwriters named in Schedule I hereto (the “Underwriters”) 5,434,783 shares of its common stock, par value $0.0001 per share (the “Firm Shares”). The Company also proposes to issue and sell to the several Underwriters not more than an additional 815,217 shares of its common stock, par value $0.0001 per share (the “Additional Shares”), if and to the extent that you, as representatives of the several Underwriters (the “Representatives”), shall have determined to exercise, on behalf of the Underwriters, the right to purchase such shares of common stock granted to the Underwriters in Section 2 hereof. The Firm Shares and the Additional Shares are hereinafter collectively referred to as the “Shares.” The shares of common stock, par value $0.0001 per share of the Company to be outstanding after giving effect to the sales contemplated hereby are hereinafter referred to as the “Common Stock.”

The Company has filed with the Securities and Exchange Commission (the “Commission”) a registration statement on Form S-3 (File No. 333-233564), which became effective on September 10, 2019 and includes a prospectus relating to the securities set forth on such Form S-3, including the Shares, to be issued from time to time by the Company. The registration statement as amended at the time it became effective, including the information (if any) deemed to be part of the registration statement at the time of effectiveness pursuant to Rule 430A or Rule 430B under the Securities Act of 1933, as amended (the “Securities Act”), is hereinafter referred to as the “Registration Statement”; the prospectus in the form first used to confirm sales of Shares (or in the form first made available to the Underwriters by the Company to meet requests of purchasers pursuant to Rule 173 under the Securities Act) is hereinafter referred to as the

“Prospectus” and the term “preliminary prospectus” means any preliminary form of the Prospectus. If the Company has filed an abbreviated registration statement to register additional shares of Common Stock pursuant to Rule 462(b) under the Securities Act (the “Rule 462 Registration Statement”), then any reference herein to the term “Registration Statement” shall be deemed to include such Rule 462 Registration Statement.

For purposes of this Agreement, “free writing prospectus” has the meaning set forth in Rule 405 under the Securities Act, “Time of Sale Prospectus” means the preliminary prospectus latest in use prior to the Applicable Time together with the documents and pricing information set forth in Schedule II hereto, and “broadly available road show” means a “bona fide electronic road show” as defined in Rule 433(h)(5) under the Securities Act that has been made available without restriction to any person. As used herein, the terms “Registration Statement,” “preliminary prospectus,” “Time of Sale Prospectus” and “Prospectus” shall include the documents, if any, incorporated by reference therein as of the date hereof. The terms “supplement,” “amendment” and “amend” as used herein with respect to the Registration Statement, the Prospectus, the Time of Sale Prospectus or any preliminary prospectus shall include all documents subsequently filed by the Company with the Commission pursuant to the Securities Exchange Act of 1934, as amended (the “Exchange Act”), that are deemed to be incorporated by reference therein.

In addition, as used in this Agreement:

“Applicable Time” means 6:00 p.m. (New York time) on the date of this Agreement or such other time as agreed to by the Company and the Representatives.

“General Use Free Writing Prospectus” means any Issuer Free Writing Prospectus (other than a broadly available road show or the pricing information identified on Schedule II hereto).

“Issuer Free Writing Prospectus” means any “issuer free writing prospectus”, as defined in Rule 433 under the Securities Act, including without limitation any “free writing prospectus” relating to the Shares that is (i) required to be filed with the Commission by the Company, (ii) a “road show that is a written communication” within the meaning of Rule 433(d)(8)(i), whether or not required to be filed with the Commission or (iii) excepted from filing with the Commission pursuant to Rule 433(d)(5)(i) because it contains a description of the Shares or of the offering that does not reflect the final terms, in each case in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained in the Company’s records pursuant to Rule 433(g).

“Limited Use Free Writing Prospectus” means any Issuer Free Writing Prospectus that is not a General Use Free Writing Prospectus.

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1. Representations and Warranties. The Company represents and warrants to and agrees with each of the Underwriters that:

(a) The Registration Statement has become effective; no stop order suspending the effectiveness of the Registration Statement is in effect, and no proceedings for such purpose are pending before or, to the knowledge of the Company, threatened by the Commission.

(b) (i) Each document, if any, filed or to be filed pursuant to the Exchange Act and incorporated by reference in the Time of Sale Prospectus or the Prospectus complied or will comply when so filed in all material respects with the Exchange Act and the applicable rules and regulations of the Commission thereunder, (ii) the Registration Statement, when it became effective, did not contain and, as amended or supplemented, if applicable, will not contain, as of the date of such amendment or supplement, any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading, (iii) the Registration Statement and the Prospectus comply and, as amended or supplemented, if applicable, will comply, as of the date of such amendment or supplement, in all material respects with the Securities Act and the applicable rules and regulations of the Commission thereunder, (iv) the Time of Sale Prospectus does not, and at the time of each sale of the Shares in connection with the offering when the Prospectus is not yet available to prospective purchasers and at the Closing Date (as defined in Section 4), the Time of Sale Prospectus, as then amended or supplemented by the Company, if applicable, will not, contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, (v) each broadly available road show, if any, when considered together with the Time of Sale Prospectus, does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading and (vi) the Prospectus does not contain and, as amended or supplemented, if applicable, will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading, except that the representations and warranties set forth in this paragraph do not apply to statements or omissions in the Registration Statement, the Time of Sale Prospectus or the Prospectus based upon information relating to any Underwriter furnished to the Company by or on behalf of any Underwriter through the Representatives, specifically for use therein, it being understood and agreed that the only such information is that described in Section 14 hereof.

(c) Any free writing prospectus that the Company is required to file pursuant to Rule 433(d) under the Securities Act has been, or will be, filed with the Commission in accordance with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Each free writing prospectus that the Company has filed, or is required to file, pursuant to Rule 433(d) under the Securities Act or that was prepared by or behalf of or used or referred to by the Company complies or, if filed after the effective date of this Agreement, will comply, when filed, in all material respects with the requirements of the Securities Act and the applicable rules and regulations of the Commission thereunder. Except for the free writing prospectuses, if any, identified in Schedule II hereto, and electronic road shows, if any, each furnished to you before first use, the Company has not prepared, used or referred to, and will not, without your prior consent, prepare, use or refer to, any free writing prospectus.

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(d) The Company has been duly organized and is validly existing as a corporation in good standing under the laws of the State of Delaware, with requisite power and authority to own or lease its properties and conduct its business as described in the Registration Statement, the Time of Sale Prospectus and the Prospectus. The Company does not own or control, directly or indirectly, any corporation, association or other entity other than the subsidiaries listed in Schedule III hereto. Each subsidiary has been duly organized and is validly existing as a corporation, limited liability company or similar entity in good standing under the laws of the jurisdiction of its organization with requisite power and authority to own or lease its properties and conduct its business as described in the Registration Statement, the Time of Sale Prospectus and the Prospectus. The Company does not have any significant subsidiaries (as defined in Rule 405 under the Securities Act). The Company and its subsidiaries are duly qualified to transact business in all jurisdictions in which the conduct of their business requires such qualification except where the failure to be so qualified would not (i) have, individually or in the aggregate, a material adverse effect on the earnings, business, properties, assets, liabilities, operations, condition (financial or otherwise) or prospects of the Company and its subsidiaries taken as a whole or (ii) prevent the consummation of the transactions contemplated hereby (the occurrence of any such effect or any such prevention described in the foregoing clauses (i) and (ii) being referred to as a “Material Adverse Effect”). The outstanding shares of capital stock of each of the Company’s subsidiaries have been duly authorized and validly issued, are fully paid and non-assessable and are owned by the Company free and clear of all liens, encumbrances and equities and claims as would not, in the aggregate, reasonably be expected to have a Material Adverse Effect; and no options, warrants or other rights to purchase, agreements or other obligations to issue or other rights to convert any obligations into shares of capital stock or ownership interests in such subsidiaries are outstanding.

(e) From the time of initial filing of the Registration Statement to the Commission through the date hereof, the Company has been and is an “emerging growth company,” as defined in Section 2(a) of the Securities Act (an “Emerging Growth Company”).

(f) The outstanding shares of Common Stock of the Company have been duly authorized and validly issued and are fully paid and non-assessable; the Shares to be issued and sold by the Company have been duly authorized and when issued and paid for as contemplated herein will be validly issued, fully paid and non-assessable; and no preemptive or similar rights of stockholders exist with respect to any of the Shares or the issue and sale thereof. Neither the filing of the Registration Statement nor the offering or sale of the Shares as contemplated by this Agreement gives rise to any rights, other than those which have been waived or satisfied, for or relating to the registration of any shares of Common Stock.

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(g) All of the Shares conform to the description thereof contained in the Registration Statement, the Time of Sale Prospectus and the Prospectus. The form of certificate for the Shares conforms to the corporate law of the jurisdiction of the Company’s incorporation and to any requirements of the Company’s organizational documents. Subsequent to the respective dates as of which information is given in the Registration Statement, the Time of Sale Prospectus and the Prospectus, except as otherwise specifically stated therein or in this Agreement, the Company has not: (i) issued any securities other than for subsequent issuances, if any, or upon the exercise of outstanding options or warrants, in each case as described in the Registration Statement, the Time of Sale Prospectus and the Prospectus; (ii) incurred any liability or obligation, direct or contingent, for borrowed money; or (iii) declared or paid any dividend or made any other distribution on or in respect to its capital stock.

(h) No Issuer Free Writing Prospectus conflicts or will conflict with the information contained in the Registration Statement or the Prospectus, and any preliminary or other prospectus deemed to be a part thereof that has not been superseded or modified.

(i) The Company has not, directly or indirectly, distributed and will not distribute any offering material in connection with the offering and sale of the Shares other than any Preliminary Prospectus, the Prospectus and other materials, if any, permitted under the Securities Act and consistent with Section 5(b) hereof.

(j) At the time of filing the Registration Statement and (ii) as of the date hereof (with such date being used as the determination date for purposes of this clause (ii)), the Company was not and is not an “ineligible issuer” (as defined in Rule 405 under the Securities Act, without taking into account any determination by the Commission pursuant to Rule 405 under the Securities Act that it is not necessary that the Company be considered an ineligible issuer), including, without limitation, for purposes of Rules 164 and 433 under the Securities Act with respect to the offering of the Shares as contemplated by the Registration Statement.

(k) The consolidated financial statements of the Company and its subsidiaries, together with related notes and schedules as set forth or incorporated by reference in the Registration Statement, the Time of Sale Prospectus and the Prospectus, comply in all material respects with the applicable requirements of the Securities Act and present fairly, in all material respects, the financial position of the Company and its subsidiaries at the indicated dates and the results of operations, changes in stockholders’ equity and cash flows of the Company and its subsidiaries for the indicated periods. Such financial statements and related schedules have been prepared in accordance with United States generally accepted principles of accounting (“GAAP”), consistently applied throughout the periods involved, except as disclosed in the related notes thereto and except in the case of unaudited financial statements, which are subject to normal and recurring year-end adjustments and do not contain certain footnotes as permitted by the applicable rules of the Commission, and all adjustments necessary for a fair presentation of results for such periods have been made. The pro forma financial information, if any, included in the Registration Statement, the Time of Sale Prospectus and the Prospectus present fairly the information shown therein, have been prepared in accordance with the Commission’s rules and guidelines with respect to pro forma financial statements, have been properly

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compiled on the pro forma bases described therein, and the assumptions used in the preparation thereof are reasonable and the adjustments used therein are appropriate to give effect to the transactions or circumstances referred to therein. The Company and its subsidiaries do not have any material liabilities or obligations, direct or contingent (including any off-balance sheet obligations or any “variable interest entities” within the meaning of Financial Accounting Standards Board Interpretation No. 46), not disclosed in the Registration Statement, the Time of Sale Prospectus and the Prospectus. There are no financial statements (historical or pro forma) that are required to be included in the Registration Statement, the Time of Sale Prospectus or the Prospectus that are not included as required.

(l) Deloitte & Touche LLP, who have certified certain of the financial statements filed with the Commission as part of the Registration Statement, the Time of Sale Prospectus and the Prospectus, is an independent registered public accounting firm with respect to the Company and its subsidiaries within the meaning of the Securities Act and the applicable rules and regulations and the Public Company Accounting Oversight Board (United States) (the “PCAOB”) as required by the Securities Act.

(m) There is and has been no failure on the part of the Company or any of the Company’s directors or officers, in their capacities as such, to comply in all material respects with any provision of the Sarbanes-Oxley Act of 2002 and the rules and regulations promulgated in connection therewith (the “Sarbanes-Oxley Act”), including Section 402 related to loans and Sections 302 and 906 related to certifications.

(n) There is no legal, governmental, administrative or regulatory investigation, action, suit, claim or proceeding pending or, to the knowledge of the Company, threatened against the Company or its subsidiaries, or to which any property of the Company or any of its subsidiaries is, or to the knowledge of the Company, would reasonably be expected to be, subject, before any court or regulatory or administrative agency or otherwise which if determined adversely to the Company or any such subsidiary would, individually or in the aggregate, have a Material Adverse Effect. There are no current or pending legal, governmental, administrative or regulatory investigations, actions, suits, claims or proceedings that are required under the Securities Act to be described in the Registration Statement, the Time of Sale Prospectus or the Prospectus that are not so described in the Registration Statement, the Time of Sale Prospectus or the Prospectus. There are no contracts or other documents that are required under the Securities Act to be filed as exhibits to the Registration Statement or described in the Registration Statement, the Time of Sale Prospectus or the Prospectus that are not so filed as exhibits to the Registration Statement or described in the Registration Statement, the Time of Sale Prospectus or the Prospectus.

(o) The Company and its subsidiaries have good and marketable title to all of the properties and assets reflected in the consolidated financial statements hereinabove described or described in the Registration Statement, the Time of Sale Prospectus and the Prospectus, subject to no lien, mortgage, pledge, charge or encumbrance of any kind except those reflected in such financial statements or described in the Registration Statement, the Time of Sale Prospectus and the Prospectus or which (i) do not materially interfere with the

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use made and proposed to be made of such property by the Company and its subsidiaries or (ii) would, individually or in the aggregate, have a Material Adverse Effect. The Company and its subsidiaries occupy their leased properties under valid and binding leases conforming in all material respects to the description thereof set forth in the Registration Statement, the Time of Sale Prospectus and the Prospectus.

(p) The Company and its subsidiaries have filed all U.S. federal, state, local and foreign tax returns which have been required to be filed and have paid all taxes indicated by such returns and all assessments received by them or any of them to the extent that such taxes have become due. All tax liabilities have been adequately provided for in the financial statements of the Company, and the Company does not know of any actual or proposed additional material tax assessments.

(q) Since the date of the most recent financial statements included or incorporated by reference in the Registration Statement, the Time of Sale Prospectus and the Prospectus, (i) there has not been any material adverse change or any development involving a prospective material adverse change in or affecting the earnings, business, management, properties, assets, rights, operations, condition (financial or otherwise), or prospects of the Company and its subsidiaries taken as a whole, whether or not occurring in the ordinary course of business, (ii) there has not been any material transaction entered into or any material transaction that is probable of being entered into by the Company or its subsidiaries, other than transactions in the ordinary course of business, as each may be amended or supplemented, and (iii) neither the Company nor its subsidiaries have sustained any loss or interference with its business that is material to the Company and its subsidiaries taken as a whole and that is either from fire, explosion, flood or other calamity, whether or not covered by insurance, or from any labor disturbance or dispute or any action, order or decree of any court or arbitrator or governmental or regulatory authority, except in each case as has been disclosed in the Registration Statement, the Time of Sale Prospectus and the Prospectus.

(r) Neither the Company nor any of its subsidiaries is or with the giving of notice or lapse of time or both, will be, (i) in violation of its certificate or articles of incorporation, charter, by-laws, certificate of formation, limited liability company agreement, partnership agreement or other organizational documents, as applicable, (ii) in violation of or in default under any agreement, lease, contract, indenture or other instrument or obligation to which it is a party or by which it, or any of its properties, is bound or (iii) in violation of any law, order, rule or regulation judgment, order, writ or decree applicable to the Company or any of its subsidiaries of any court or of any government, regulatory body or administrative agency or other governmental body having jurisdiction over the Company or such subsidiary, or any of their properties or assets, except in the case of clauses (ii) and (iii), for such violations or defaults as would not, individually or in the aggregate, have a Material Adverse Effect. The execution and delivery of this Agreement and the consummation of the transactions herein contemplated and the fulfillment of the terms hereof do not and will not conflict with or result in a breach of any of the terms or provisions of, or constitute a default under, (A) any indenture, mortgage, deed of trust or other agreement or instrument to which the Company or any of its subsidiaries is a party or by which the Company or any of its

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subsidiaries or any of their respective properties is bound, or of (B) the certificate of incorporation or formation, articles of incorporation or association, charter, by-laws or other organizational documents, as applicable, of the Company or (C) any law, order, rule or regulation judgment, order, writ or decree applicable to the Company or any of its subsidiaries of any court or of any government, regulatory body or administrative agency or other governmental body having jurisdiction over the Company or any such subsidiary, or any of their properties or assets, except, with respect to (A) and (C), for such violations as would not, individually or in the aggregate, result in a Material Adverse Effect.

(s) The execution and delivery of, and the performance by the Company of its obligations under, this Agreement has been duly and validly authorized by all necessary corporate, limited liability company or similar applicable action on the part of the Company, and this Agreement has been duly executed and delivered by the Company.

(t) Each approval, consent, order, authorization, designation, declaration or filing by or with any regulatory, administrative or other governmental body necessary in connection with the execution and delivery by the Company of this Agreement and the consummation of the transactions herein contemplated has been obtained or made and is in full force and effect (except such additional steps as may be required by the Commission, the Financial Industry Regulatory Authority, Inc. (“FINRA”) or such additional steps as may be necessary to qualify the Shares for public offering by the Underwriters under state securities or Blue Sky laws). All of the information provided to the Underwriters or counsel to the Underwriters by the Company, its counsel, its officers and directors and the holders of any securities or options to acquire any securities of the Company in connection with the offering of the Shares is true, complete and correct in all material respects, and is compliant with FINRA’s rules . Any letters, filings or other supplemental information provided to FINRA pursuant to FINRA Rules or NASD Conduct Rules is true, complete and correct in all material respects.

(u) Except as would not, individually or in the aggregate, have a Material Adverse Effect, the Company and its subsidiaries (i) hold all licenses, registrations, certificates and permits from governmental authorities (collectively, “Governmental Licenses”), which are necessary to the conduct of their business, (ii) are in compliance with the terms and conditions of all Governmental Licenses, and all Governmental Licenses are valid and in full force and effect, and (iii) have not received any written or other notice of proceedings relating to the revocation or modification of any Governmental License.

(v) Except as otherwise disclosed in the Registration Statement, the Time of Sale Prospectus, and the Prospectus, the Company and its subsidiaries own or have obtained licenses for all patents, patent applications, inventions, trademarks, trade names, service marks, logos, trade dress, designs, data, database rights, Internet domain names, rights of privacy, rights of publicity, copyrights, works of authorship, license rights, trade secrets, know-how and proprietary information (including unpatented and unpatentable proprietary or confidential information, inventions, systems or procedures) and other industrial property and intellectual property rights described in the Registration Statement, the Time of Sale Prospectus, and the Prospectus as being owned or licensed by them, as

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well as related rights, such as moral rights and the right to sue for all past, present and future infringements or misappropriations of any of the foregoing, and registrations and applications for registration of any of the foregoing (collectively, “Intellectual Property”) necessary in all material respects for the conduct of their business as presently conducted and as presently proposed to be conducted in the future as disclosed in the Registration Statement, the Time of Sale Prospectus, and the Prospectus, and such Intellectual Property has not been adjudged by a court of competent jurisdiction to be invalid or unenforceable, in whole or in part. Neither the Company nor any of its subsidiaries has materially infringed, misappropriated, otherwise violated, or is currently materially infringing, misappropriating, or otherwise violating, and none of the Company or any of its subsidiaries has received any communication or notice of infringement of, misappropriation of, conflict with or violation of, any Intellectual Property of any other person or entity. To the Company’s knowledge: (i) there are no third parties who have rights to any Intellectual Property, except for (x) customary reversionary rights of third-party licensors with respect to Intellectual Property that are disclosed in the Registration Statement, the Time of Sale Prospectus, and the Prospectus as licensed to the Company or its subsidiaries and (y) third parties who have been explicitly granted licenses by the Company; and (ii) there is no infringement by third parties of any Intellectual Property. There is no pending or, to the Company’s knowledge, threatened action, suit, proceeding or claim by others: (A) challenging the Company’s rights in or to any Intellectual Property, and the Company is unaware of any facts which would form a reasonable basis for any such action, suit, proceeding or claim; (B) challenging the validity, enforceability or scope of any Intellectual Property, and the Company is unaware of any facts which would form a reasonable basis for any such action, suit, proceeding or claim; or (C) asserting that the Company infringes, misappropriates, or otherwise violates, or would, upon the commercialization of any product or service described in the Registration Statement, the Time of Sale Prospectus or the Prospectus as under development, infringe, misappropriate, or violate, any patent, trademark, trade name, service name, copyright, trade secret or other proprietary rights of others, and the Company is unaware of any facts which would form a reasonable basis for any such action, suit, proceeding or claim. The Company and its subsidiaries have complied in all material respects with the terms of each agreement pursuant to which Intellectual Property has been licensed to the Company, and all such agreements are in full force and effect. The Company and its subsidiaries have taken all reasonable steps necessary to secure their interests in the Intellectual Property from their employees and contractors and to protect the confidentiality of all of their confidential information and trade secrets. The product candidates described in the Registration Statement, the Time of Sale Prospectus and the Prospectus as under development by the Company fall within the scope of the claims of one or more patents or patent applications owned by, or exclusively licensed to, the Company. To the Company’s knowledge, there is no patent or published patent application in the U.S. or other jurisdiction which contains claims that dominate or may dominate the Intellectual Property described in the Registration Statement, the Time of Sale Prospectus and the Prospectus or that interferes with the issued or pending claims of any such Intellectual Property (for the avoidance of doubt, the Company makes no such representation as to the intellectual property covering PD1/PD-L1 inhibitors described therein as owned or controlled by third parties). There is no prior art of which the Company is aware that

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would render any patent held by the Company invalid, except as would not, individually or in the aggregate, have a Material Adverse Effect, and all prior art of which the Company is aware that may be material to the validity of a U.S. patent or to the patentability of a U.S. patent application has been disclosed to the U.S. Patent and Trademark Office, and all such prior art has been disclosed to the patent office of other jurisdictions where required. To the Company’s knowledge, there are no material defects in any of the patents or patent applications included in the Intellectual Property. To the Company’s knowledge, the duties of candor and good faith required by the United States Patent and Trademark Office during the prosecution of the United States patents and patent applications included in the Intellectual Property have been complied with, and all such requirements in foreign offices having similar requirements applicable to the Company or its subsidiaries have been complied with. To the Company’s knowledge, no employee of the Company is in or has been in violation of any term of any employment contract, patent disclosure agreement, invention assignment agreement, non-competition agreement, non-solicitation agreement, nondisclosure agreement or any restrictive covenant to or with a former employer where the basis of such violation relates to such employee’s employment with the Company.

(w) The Company and its subsidiaries’ information technology assets and equipment, computers, systems, networks, hardware, software, websites, applications, and databases (collectively, “IT Systems”) are adequate for, and operate and perform in all material respects as required in connection with the operation of the business of the Company and its subsidiaries as currently conducted, free and clear of all material bugs, errors, defects, Trojan horses, time bombs, malware and other corruptants. The Company and its subsidiaries have implemented and maintained commercially reasonable controls, policies, procedures, and safeguards to maintain and protect their material confidential information and the integrity, continuous operation, redundancy and security of all IT Systems and data (including all personal, personally identifiable, sensitive, confidential or regulated data (“Personal Data”)) used in connection with their businesses, and there have been no breaches, violations, outages or unauthorized uses of or accesses to same, except for those that have been remedied without material cost or liability or the duty to notify any other person, nor any incidents under internal review or investigations relating to the same. The Company and its subsidiaries are presently in material compliance with all applicable laws or statutes and all judgments, orders, rules and regulations of any court or arbitrator or governmental or regulatory authority, internal policies and contractual obligations relating to the privacy and security of IT Systems and Personal Data and to the protection of such IT Systems and Personal Data from unauthorized use, access, misappropriation or modification. The Company and its subsidiaries have taken all necessary actions to prepare to comply with the European Union General Data Protection Regulation (and all other applicable laws and regulations with respect to Personal Data that have been announced as of the date hereof as becoming effective within 12 months after the date hereof, and for which any non-compliance with same would be reasonably likely to create a material liability) as soon they take effect.

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(x) None of the Intellectual Property or technology (including information technology and outsourced arrangements) employed by the Company or its subsidiaries has been obtained or is being used by the Company or its subsidiaries in violation of any contractual obligation binding on the Company or its subsidiaries or any of their respective officers, directors or employees or otherwise in violation of the rights of any persons.

(y) None of the Company or its subsidiaries nor, to the Company’s knowledge, any of their affiliates, has taken or may take, directly or indirectly, any action designed to cause or result in, or which has constituted or which might reasonably be expected to constitute, the stabilization or manipulation of the price of the shares of Common Stock to facilitate the sale or resale of the Shares.

(z) Neither the Company nor any of its subsidiaries is or, after giving effect to the offering and sale of the Shares contemplated hereunder and the application of the net proceeds from such sale as described in the Registration Statement, the Time of Sale Prospectus and the Prospectus, will be required to register as an “investment company” or an entity “controlled” by an “investment company” within the meaning of the Investment Company Act of 1940, as amended, and the rules and regulations of the Commission thereunder (collectively, the “1940 Act”).

(aa) The Company maintains a system of “internal control over financial reporting” (as defined in Rule 13a-15(f) of the Exchange Act) that comply with the requirements of the Exchange Act and have been designed by, or under the supervision of, their respective principal executive and principal financial officers, or persons performing similar functions, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with GAAP, including, but not limited to, internal accounting controls sufficient to provide reasonable assurance that: (i) transactions are executed in accordance with management’s general or specific authorization; (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with GAAP and to maintain accountability for assets; (iii) access to assets is permitted only in accordance with management’s general or specific authorization; and (iv) the recorded accountability for assets is compared with existing assets at reasonable intervals and appropriate action is taken with respect to any differences. Other than as described in the Registration Statement, Time of Sale Prospectus and the Prospectus, there are no material weaknesses in the Company’s internal control over financial reporting, and there has been no change in internal control over financial reporting that has materially affected, or is reasonably likely to materially affect, the Company’s internal control over financial reporting since the respective dates as of which information is given in the Registration Statement, the Time of Sale Prospectus and the Prospectus. The Company’s auditors and the Audit Committee of the Board of Directors of the Company have been advised of: (i) all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which have adversely affected or are reasonably likely to adversely affect the Company’s ability to record, process, summarize and report financial information; and (ii) any fraud, whether or not material, that involves management or other employees who have a significant role in the Company’s internal controls over financial reporting.

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(bb) The Company has established and maintains “disclosure controls and procedures” (as defined in Rules 13a-14(c) and 15d-14(c) under the Exchange Act); the Company’s “disclosure controls and procedures” are reasonably designed to ensure that all information (both financial and non-financial) required to be disclosed by the Company in the reports that it files or submits under the Exchange Act is recorded, processed, summarized and reported within the time periods specified in the rules and regulations under the Exchange Act, and that all such information is accumulated and communicated to the Company’s management as appropriate to allow timely decisions regarding required disclosure and to make the certifications of the Chief Executive Officer and Chief Financial Officer of the Company required under the Exchange Act with respect to such reports.

(cc) The statistical, industry-related and market-related data included or incorporated by reference in the Registration Statement, the Time of Sale Prospectus and the Prospectus are based on or derived from sources which the Company reasonably and in good faith believes are reliable and accurate, and such data agree with the sources from which they are derived. To the extent required, the Company has obtained the written consent to the use of such data from such sources.

(dd) The operations of the Company and its subsidiaries are and have been conducted at all times in compliance with all applicable financial recordkeeping and reporting requirements, including those of the Bank Secrecy Act, as amended by Title III of the Uniting and Strengthening America by Providing Appropriate Tools Required to Intercept and Obstruct Terrorism Act of 2001 (USA PATRIOT Act), the Currency and Foreign Transactions Reporting Act of 1970, as amended, and the applicable anti-money laundering statutes of jurisdictions where the Company and its subsidiaries conduct business, the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any governmental agency (collectively, the “Anti-Money Laundering Laws”), and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or any of its subsidiaries with respect to the Anti-Money Laundering Laws is pending or, to the best knowledge of the Company, threatened.

(ee) Neither the Company nor its subsidiaries or any of their directors or officers nor, to the Company’s knowledge, any employee, agent, affiliate or representative of the Company or its subsidiaries, is an individual or entity (“Person”) that is, or is owned or controlled by a Person that is: (A) the subject of any sanctions administered or enforced by the U.S. Department of Treasury’s Office of Foreign Assets Control (“OFAC”), the United Nations Security Council (“UNSC”), the European Union (“EU”), Her Majesty’s Treasury (“HMT”) or other relevant sanctions authority (collectively, “Sanctions”), nor (B) located, organized or resident in a country or territory that is the subject of Sanctions (including, without limitation, Cuba, Iran, North Korea, Sudan, Syria and the Crimea). The Company will not, directly or indirectly, use the proceeds of the offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other Person: to fund or facilitate any activities or business of or with any Person or in any country or territory that, at the time of such funding or facilitation, is the subject of Sanctions; or in any other manner that will result in a violation of Sanctions by any Person (including any Person participating in the offering, whether as underwriter, advisor, investor or otherwise). For the past five years, the Company and its subsidiaries have not knowingly engaged in, are not now knowingly engaged in, and will not engage in, any dealings or transactions with any Person, or in any country or territory, that at the time of the dealing or transaction is or was the subject of Sanctions.

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(ff) Neither the Company nor its subsidiaries or any of their directors or officers nor, to the Company’s knowledge, any employee, agent, affiliate or representative of the Company or its subsidiaries, has taken or will take any action in furtherance of an offer, payment, promise to pay, or authorization or approval of the payment or giving of money, property, gifts or anything else of value, directly or indirectly, to any “government official” (including any officer or employee of a government or government-owned or controlled entity or of a public international organization, or any person acting in an official capacity for or on behalf of any of the foregoing, or any political party or party official or candidate for political office) to influence official action or secure an improper advantage; and the Company and its subsidiaries and affiliates have conducted their businesses in compliance with the OECD Convention on Bribery of Foreign Public Officials in International Business Transactions (“OECD Convention”), the Foreign Corrupt Practices Act of 1977, as amended, and the rules and regulations thereunder (collectively, the “FCPA”), the U.K. Bribery Act 2010 or any similar law or regulation to which the Company, its subsidiaries, any director, officer, agent, employee, affiliate or other person associated with or acting on behalf of the Company or its subsidiaries is subject, and they have instituted and maintain and will continue to maintain policies and procedures designed to promote and achieve compliance with such laws and with the representation and warranty contained herein.

(gg) Company carries, or is covered by, insurance, from insurers of recognized financial responsibility, in such amounts and covering such risks as is adequate for the conduct of its businesses and the value of its properties and as is prudent and customary for a company engaged in a similar business; the Company has not been refused any coverage under insurance policies sought or applied for; and the Company has no reason to believe that it will not be able to renew its existing insurance coverage as and when such coverage expires or to obtain similar coverage from similar insurers as may be necessary to continue its business at a cost that would not, individually or in the aggregate, have a Material Adverse Effect.

(hh) Each “employee benefit plan” (within the meaning of Section 3(3) of the Employee Retirement Income Security Act of 1974, as amended, including the regulations and published interpretations thereunder (“ERISA”)) for which the Company or any member of its “Controlled Group” (defined as any organization that is a member of a controlled group of corporations within the meaning of Section 414 of the Internal Revenue Code of 1986, as amended (the “Code”)), including its subsidiaries, would have liability (each a “Plan”) is in compliance in all material respects with all presently applicable statutes, rules and regulations, including ERISA and the Code; (ii) with respect to each Plan subject to Title IV of ERISA (a) no “reportable event” (as defined in Section 4043 of ERISA) has occurred for which the Company or any member of its Controlled Group would have any liability; and (b) neither the Company nor any member of its Controlled Group has incurred or expects to incur liability under Title IV of ERISA (other than for contributions to the Plan or premiums payable to the Pension Benefit

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Guaranty Corporation, in each case in the ordinary course and without default); (iii) no Plan which is subject to Section 412 of the Code or Section 302 of ERISA has failed to satisfy the minimum funding standard within the meaning of such sections of the Code or ERISA; and (iv) each Plan that is intended to be qualified under Section 401(a) of the Code is so qualified and nothing has occurred, whether by action or by failure to act, which would cause the loss of such qualification.

(ii) There are no affiliations or associations between any member of FINRA and any of the Company’s or its subsidiaries’ officers, directors or 5% or greater securityholders.

(jj) Except in each case as otherwise disclosed or incorporated by reference in the Registration Statement, the Time of Sale Prospectus and the Prospectus: (i) the Company and its subsidiaries have complied and are in compliance, in all material respects, with all applicable federal, state, local, foreign and international laws (including the common law), statutes, rules, regulations, orders, judgments, decrees or other legally binding requirements of any court, administrative agency or other governmental authority relating to pollution or to the protection of the environment, natural resources or human health or safety, or to the manufacture, use, generation, treatment, storage, disposal, release or threatened release of hazardous or toxic substances, pollutants, contaminants or wastes, or the arrangement for such activities (“Environmental Laws”); (ii) the Company and its subsidiaries have obtained and are in compliance, in all material respects, with all permits, licenses, authorizations or other approvals required of them under Environmental Laws to conduct their respective businesses and are not subject to any action to revoke, terminate, cancel, limit, amend or appeal any such permits, licenses, authorizations or approvals; (iii) neither the Company nor its subsidiaries is a party to any judicial or administrative proceeding (including a notice of violation) under any Environmental Laws (a) to which a governmental authority is also a party and which involves potential monetary sanctions, unless it could reasonably be expected that such proceeding will result in monetary sanctions of less than $100,000, or (b) which is otherwise material; and no such proceeding has been threatened or is known to be contemplated; (iv) neither the Company nor its subsidiaries has received notice or is otherwise aware of any pending or threatened material claim or potential liability under Environmental Laws in respect of its past or present business, operations (including the disposal of hazardous substances at any off-site location), facilities or real property (whether owned, leased or operated) or on account of any predecessor or any person whose liability under any Environmental Laws it has agreed to assume; and neither the Company nor its subsidiaries is aware of any facts or conditions that could reasonably be expected to give rise to any such claim or liability; and (v) neither the Company nor its subsidiaries is aware of any matters regarding compliance with existing or reasonably anticipated Environmental Laws, or with any liabilities or other obligations under Environmental Laws (including asset retirement obligations), that could reasonably be expected to have a material effect on the capital expenditures, earnings or competitive position of the Company and its subsidiaries.

(kk) The Shares have been approved for listing subject to notice of issuance on the NASDAQ Global Select Market.

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(ll) There are no relationships, direct or indirect, or related-party transactions involving the Company or its subsidiaries or any other person required to be described in the Registration Statement and the Prospectus which have not been described in such documents and the Time of Sale Prospectus as required.

(mm) No subsidiary of the Company is currently prohibited, directly or indirectly, from paying any dividends to the Company, from making any other distribution on such subsidiary’s capital stock, from repaying to the Company any loans or advances to such subsidiary from the Company or from transferring any of such subsidiary’s property or assets to the Company or any other subsidiary of the Company.

(nn) No labor disturbance by or dispute with employees of the Company or its subsidiaries exists or, to the knowledge of the Company, is contemplated or threatened.

(oo) Neither the Company nor its subsidiaries is a party to any contract, agreement or understanding with any person (other than this Agreement) that would give rise to a valid claim against the Company or its subsidiaries or any Underwriter for a brokerage commission, finder’s fee or like payment in connection with the offering and sale of the Shares.

(pp) The preclinical tests and clinical trials, and other studies (collectively, “studies”) that are described in, or the results of which are referred to in, the Registration Statement, the Time of Sale Prospectus or the Prospectus were and, if still pending, are being conducted in all material respects in accordance with the protocols, procedures and controls designed and approved for such studies and with standard medical and scientific research procedures; each description of the results of such studies is accurate and complete in all material respects and fairly presents the data derived from such studies, and the Company has no knowledge of any other studies the results of which are inconsistent with, or otherwise call into question, the results described or referred to in the Registration Statement, the Time of Sale Prospectus or the Prospectus; the Company or, to the Company’s knowledge, the clinical trial sponsor of the trials or studies, has made all such filings and obtained all such approvals or authorizations as may be required by the Food and Drug Administration of the U.S. Department of Health and Human Services or from any other U.S. or foreign government or drug or medical device regulatory agency, or health care facility Institutional Review Board or independent ethics committee (collectively, the “Regulatory Agencies”), except where the failure to make such filing or obtain such approval would not reasonably be expected to, individually or in the aggregate, result in a Material Adverse Effect; except as described in the Registration Statement, the Time of Sale Prospectus and the Prospectus, the Company and, to the Company’s knowledge, the clinical trial sponsor of such trials, has not received any notice of, or correspondence from, any Regulatory Agency requiring the termination, suspension or material modification of any clinical trials that are described or referred to in the Registration Statement, the Time of Sale Prospectus, nor is the Company aware of any reasonable grounds for such notice or correspondence; and the Company has operated and currently is in compliance in all material respects with all applicable rules and regulations of the Regulatory Agencies.

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(qq) The Company and its subsidiaries are, and at all times have been, in compliance with all state, federal and foreign Health Care Laws applicable to the Company and its Subsidiaries’ respective businesses, and the Company and its Subsidiaries are in compliance with Health Care Laws, except where the failure to do so would not reasonably be expected to have a Material Adverse Effect. The Company and its Subsidiaries have not engaged in activities which to its knowledge are cause for false claims liability, civil penalties, or mandatory or permissive exclusion from Medicare, Medicaid, or any other state health care program or federal health care program. For purposes of this Agreement, “Health Care Laws” means the: (i) the Federal Food, Drug, and Cosmetic Act (21 U.S.C. § 301 et seq.) and the regulations promulgated thereunder; (ii) all applicable federal, state, local and foreign health care related fraud and abuse laws, including, without limitation, the U.S. Anti-Kickback Statute (42 U.S.C. Section 1320a-7b(b)), the U.S. civil False Claims Act (31 U.S.C. Section 3729 et seq.), the federal criminal false claims law (42 U.S.C. § 1320a-7b(a)), the federal civil monetary penalties law (42 U.S.C. § 1320a-7a), the Stark Law (42 U.S.C. §1395nn), 18 U.S.C. Sections 286 and 287, the health care fraud criminal provisions under the U.S. Health Insurance Portability and Accountability Act of 1996 (“HIPAA”) (42 U.S.C. Section 1320d et seq.), the exclusion laws (42 U.S.C. §1320a-7), the statutes and regulations government healthcare programs, including the European Union General Data Protection Regulation (EU 2016 679), Medicare, Title XVIII of the Social Security Act, and Medicaid, Title XIX of the Social Security Act, and the regulations promulgated pursuant to such statutes; (iii) the U.S. federal Prescription Drug Marketing Act of 1987, as amended, and the regulations promulgated thereunder; (iv) the U.S. Controlled Substances Act; (v) the Clinical Laboratory Improvement Act; and (vi) the Standards for Privacy of Individually Identifiable Health Information (the “Privacy Rule”), the Security Standards, and the Standards for Electronic Transactions and Code Sets promulgated under HIPAA, the Health Information Technology for Economic and Clinical Health Act (42 U.S.C. Section 17921 et seq.), and the regulations promulgated thereunder and any state or non-U.S. counterpart thereof or other law or regulation the purpose of which is to protect the privacy of individuals or prescribers. Neither the Company nor its Subsidiaries have received written notice of any claim, action, suit, proceeding, hearing, enforcement, investigation, arbitration or other material action from any court or arbitrator or governmental or regulatory authority or third party alleging that any product, operation or activity is in violation of any Health Care Laws nor, to the Company’s knowledge, is any such claim, action, suit, proceeding, hearing, enforcement, investigation, arbitration or other action threatened. The Company and its Subsidiaries have filed, maintained or submitted all material reports, documents, forms, notices, applications, records, claims, submissions and supplements or amendments as required by any Health Care Laws, and all such reports, documents, forms, notices, applications, records, claims, submissions and supplements or amendments were complete and accurate on the date filed in all material respects (or were corrected or supplemented by a subsequent submission). Neither the Company nor its Subsidiaries are a party to any corporate integrity agreements, monitoring agreements, consent decrees, plans of correction, settlement orders, or similar agreements with or imposed by any governmental or regulatory authority. Additionally, neither the Company, its Subsidiaries nor any of their respective employees, officers or directors has been excluded, suspended or debarred from

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participation in any U.S. federal health care program or human clinical research or, to the knowledge of the Company, is subject to a governmental inquiry, investigation, proceeding, or other similar action that would reasonably be expected to result in debarment, suspension, or exclusion. The Company and its subsidiaries have filed, obtained, maintained or submitted all material reports, documents, forms, notices, applications, records, claims, submissions and supplements or amendments as required by the Health Care Laws, and all such reports, documents, forms, notices, applications, records, claims, submissions and supplements or amendments were timely, complete, accurate and not misleading on the date filed in all material respects (or were corrected or supplemented by a subsequent submission).

(rr) The interactive data in eXtensible Business Reporting Language included or incorporated by reference in the Registration Statement fairly presents the information called for in all material respects and has been prepared in accordance with the Commission’s rules and guidelines applicable thereto.

(ss) (i) Except as may be included or incorporated by reference in the Registration Statement, the Time of Sale Prospectus and the Prospectus, (x) to the Company’s knowledge, there has been no material security breach or other material compromise of or relating to any of the Company’s or its subsidiaries’ information technology and computer systems, networks, hardware, software, data (including the data of their respective customers, employees, suppliers, vendors and any third party data maintained by or on behalf of them), equipment or technology (collectively, “IT Systems and Data”) and (y) the Company and its subsidiaries have not been notified of, and have no knowledge of any event or condition that would reasonably be expected to result in, any material security breach or other material compromise to their IT Systems and Data; (ii) the Company and its subsidiaries are presently in compliance with all applicable laws or statutes and all judgments, orders, rules and regulations of any court or arbitrator or governmental or regulatory authority, internal policies and contractual obligations relating to the privacy and security of IT Systems and Data and to the protection of such IT Systems and Data from unauthorized use, access, misappropriation or modification, except as would not, in the case of this clause (ii), individually or in the aggregate, have a material adverse effect on the financial condition, business or properties of the Company and its subsidiaries considered as one enterprise; and (iii) the Company and its subsidiaries have implemented backup and disaster recovery technology consistent with industry standards and practices.

(tt) The Company (i) has not engaged in any Testing-the-Waters Communication, and (ii) has not authorized anyone to engage in Testing-the-Waters Communications. The Company has not distributed any Written Testing-the-Waters Communications. “Testing-the-Waters Communication” means any oral or written communication with potential investors undertaken in reliance on Section 5(d) of the Securities Act. “Written Testing-the-Waters Communication” means any Testing-the-Waters Communication that is a written communication within the meaning of Rule 405 under the Securities Act.

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2. Agreements to Sell and Purchase. The Company hereby agrees to sell to the several Underwriters, and each Underwriter, upon the basis of the representations and warranties herein contained, but subject to the conditions hereinafter stated, agrees, severally and not jointly, to purchase from the Company the respective numbers of Firm Shares set forth in Schedule I hereto opposite its name at $21.6200 a share (the “Purchase Price”).

On the basis of the representations and warranties contained in this Agreement, and subject to its terms and conditions, the Company agrees to sell to the Underwriters the Additional Shares, and the Underwriters shall have the right to purchase, severally and not jointly, up to 815,217 Additional Shares at the Purchase Price, provided, however, that the amount paid by the Underwriters for any Additional Shares shall be reduced by an amount per share equal to any dividends declared by the Company and payable on the Firm Shares but not payable on such Additional Shares. You may exercise this right on behalf of the Underwriters in whole or from time to time in part by giving written notice to the Company not later than 30 days after the date of this Agreement. Any exercise notice shall specify the number of Additional Shares to be purchased by the Underwriters and the date on which such shares are to be purchased. Each purchase date must be at least one business day after the written notice is given and may not be earlier than the closing date for the Firm Shares nor later than 10 business days after the date of such notice. On each day, if any, that Additional Shares are to be purchased (an “Option Closing Date”), each Underwriter agrees, severally and not jointly, to purchase the number of Additional Shares (subject to such adjustments to eliminate fractional shares as you may determine) that bears the same proportion to the total number of Additional Shares to be purchased on such Option Closing Date as the number of Firm Shares set forth in Schedule I hereto opposite the name of such Underwriter bears to the total number of Firm Shares.

3. Terms of Public Offering. The Company is advised by you that the Underwriters propose to make a public offering of their respective portions of the Shares as soon after the Registration Statement and this Agreement have become effective as in your judgment is advisable. The Company is further advised by you that the Shares are to be offered to the public initially at $23.00 a share (the “Public Offering Price”).

4. Payment and Delivery. Payment for the Firm Shares shall be made to the Company in Federal or other funds immediately available in New York City against delivery of such Firm Shares for the respective accounts of the several Underwriters at 10:00 a.m., New York City time, on December 11, 2020, or at such other time on the same or such other date, not later than December 18, 2020, as shall be designated in writing by you. The time and date of such payment are hereinafter referred to as the “Closing Date.”

Payment for any Additional Shares shall be made to the Company in Federal or other funds immediately available in New York City against delivery of such Additional Shares for the respective accounts of the several Underwriters at 10:00 a.m., New York City time, on the date specified in the corresponding notice described in Section 2 or at such other time on the same or on such other date, in any event not later than January 11, 2021, as shall be designated in writing by you.

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The Firm Shares and Additional Shares shall be registered in such names and in such denominations as you shall request in writing not later than one full business day prior to the Closing Date or the applicable Option Closing Date, as the case may be. The Firm Shares and Additional Shares shall be delivered to you on the Closing Date or an Option Closing Date, as the case may be, for the respective accounts of the several Underwriters, with any transfer taxes payable in connection with the transfer of the Shares to the Underwriters duly paid, against payment of the Purchase Price therefor.

5. Covenants of the Company. The Company covenants with each Underwriter as follows:

(a) The Company will (i) prepare and timely file with the Commission under Rule 424(b) under the Securities Act a Prospectus in a form approved by the Representatives containing information previously omitted at the time of effectiveness of the Registration Statement in reliance on Rules 430A, 430B or 430C under the Securities Act, and (ii) not file any amendment to the Registration Statement or any documents incorporated by reference therein or distribute an amendment or supplement to the Time of Sale Prospectus or the Prospectus of which the Representatives shall not previously have been advised and furnished with a copy or to which the Representatives shall have reasonably objected in writing or which is not in compliance with the rules and regulations of the Securities Act.

(b) The Company will (i) not make any offer relating to the Shares that would constitute an Issuer Free Writing Prospectus or that would otherwise constitute a “free writing prospectus” (as defined in Rule 405 under the Securities Act) required to be filed by the Company with the Commission under Rule 433 under the Securities Act unless the Representatives approve its use in writing prior to first use (each, a “Permitted Free Writing Prospectus”); provided that the prior written consent of the Representatives hereto shall be deemed to have been given in respect of the Issuer Free Writing Prospectus(es) included on Schedule II hereto, (ii) treat each Permitted Free Writing Prospectus as an Issuer Free Writing Prospectus, (iii) comply with the requirements of Rules 164 and 433 under the Securities Act applicable to any Issuer Free Writing Prospectus, including the requirements relating to timely filing with the Commission, legending and record keeping and (iv) not take any action that would result in an Underwriter or the Company being required to file with the Commission pursuant to Rule 433(d) under the Securities Act a free writing prospectus prepared by or on behalf of such Underwriter that such Underwriter otherwise would not have been required to file thereunder.

(c) The Company will promptly notify the Representatives if the Company ceases to be an Emerging Growth Company at any time prior to the later of (i) completion of the distribution of the Shares within the meaning of the Securities Act and (ii) completion of the 60-day restricted period referred to in Section 5(k) hereof.

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(d) The Company will advise the Representatives promptly (i) when any post-effective amendment to the Registration Statement shall have become effective, (ii) of receipt of any comments from the Commission, (iii) when any supplement to the Prospectus, any Issuer Free Writing Prospectus, or any amendment to the Prospectus has been filed, (iv) of any request of the Commission for amendment of the Registration Statement or for supplement to the Time of Sale Prospectus or the Prospectus or for any additional information, (v) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or any order preventing or suspending the use of any Preliminary Prospectus, any Issuer Free Writing Prospectus, or the Prospectus, or of the institution of any proceedings for that purpose or pursuant to Section 8A of the Securities Act, (vi) of the occurrence of any event or development within the Prospectus Delivery Period (as defined below) as a result of which the Prospectus, the Time of Sale Prospectus or any Issuer Free Writing Prospectus as then amended or supplemented would include any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances existing when the Prospectus, the Time of Sale Prospectus or any such Issuer Free Writing Prospectus is delivered to a purchaser, not misleading, and (vii) of the receipt by the Company of any notice with respect to any suspension of the qualification of the Shares for offer and sale in any jurisdiction or the initiation or, to the knowledge of the Company, threatening of any proceeding for such purpose. The Company will use its best efforts to prevent the issuance of any order, suspension or qualification referred to in clause (v) or (vii) of this paragraph and to obtain as soon as possible the lifting thereof, if issued.

(e) The Company will cooperate with the Representatives in endeavoring to qualify the Shares for sale under the securities laws of such jurisdictions as the Representatives may reasonably have designated in writing and will make such applications, file such documents, and furnish such information as may be reasonably required for that purpose; provided that the Company shall not be required to (i) qualify as a foreign corporation, (ii) file a general consent to service of process in any jurisdiction where it is not now so qualified or required to file such a consent, or (iii) subject itself to taxation in any such jurisdiction if it is not otherwise so subject. The Company will, from time to time, prepare and file such statements, reports, and other documents, as are or may be required to continue such qualifications in effect for so long a period as the Representatives may reasonably request for distribution of the Shares.

(f) The Company will deliver to, or upon the order of, the Representatives, from time to time, as many copies of any Preliminary Prospectus as the Representatives may reasonably request. The Company will deliver to, or upon the order of, the Representatives, from time to time, as many copies of any Issuer Free Writing Prospectus as the Representatives may reasonably request. The Company will deliver to, or upon the order of, the Representatives during the period when delivery of a Prospectus (or, in lieu thereof, the notice referred to under Rule 173(a) under the Securities Act) (the “Prospectus Delivery Period”) is required under the Securities Act, as many copies of the Prospectus in final form, or as thereafter amended or supplemented, as the Representatives may reasonably request. If requested, the Company will deliver to the Representatives at or before the Closing Date, four signed copies of the Registration Statement and all amendments thereto

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including all exhibits filed therewith, and will deliver to the Representatives such number of copies of the Registration Statement (including such number of copies of the exhibits filed therewith that may reasonably be requested), and of all amendments thereto, as the Representatives may reasonably request.

(g) The Company will comply with the Securities Act and the rules and regulations of the Commission promulgated thereunder, and the Exchange Act, and the rules and regulations of the Commission thereunder, so as to permit the completion of the distribution of the Shares as contemplated in this Agreement and the Prospectus. If during the period in which a prospectus (or, in lieu thereof, the notice referred to under Rule 173(a) under the Securities Act) is required by law to be delivered by an Underwriter or dealer, any event or development shall occur as a result of which, in the judgment of the Company or in the opinion of the Underwriters, it becomes necessary to amend or supplement the Prospectus in order to make the statements therein, in the light of the circumstances existing at the time the Prospectus is delivered to a purchaser, not misleading, or, if it is necessary at any time to amend or supplement the Prospectus to comply with any law, the Company promptly will prepare and file with the Commission an appropriate amendment to the Registration Statement or supplement to the Prospectus so that the Prospectus as so amended or supplemented will not, in the light of the circumstances when it is so delivered, be misleading, or so that the Prospectus will comply with the law.

(h) If the Time of Sale Prospectus is being used to solicit offers to buy the Shares at a time when the Prospectus is not yet available to prospective purchasers and any event or development shall occur or condition shall exist as a result of which, in the judgment of the Company or in the opinion of the Underwriters, it becomes necessary to amend or supplement the Time of Sale Prospectus in order to make the statements therein, in the light of the circumstances, not misleading, or to make the statements therein not conflict with the information contained in the Registration Statement then on file, or if it is necessary at any time to amend or supplement the Time of Sale Prospectus to comply with any law, the Company promptly will prepare, file with the Commission (if required) and furnish to the Underwriters and any dealers an appropriate amendment or supplement to the Time of Sale Prospectus so that the Time of Sale Prospectus as so amended or supplemented will not, in the light of the circumstances, be misleading or conflict with the Registration Statement then on file, or so that the Time of Sale Prospectus will comply with law.

(i) The Company will make generally available to its security holders, as soon as it is practicable to do so, but in any event not later than 15 months after the effective date of the Registration Statement, an earnings statement (which need not be audited) in reasonable detail, covering a period of at least 12 consecutive months beginning after the effective date of the Registration Statement, which earnings statement shall satisfy the requirements of Section 11(a) of the Securities Act and Rule 158 under the Securities Act and will advise you in writing when such statement has been so made available.

(j) Prior to the Closing Date, the Company will furnish to the Underwriters, as soon as they have been prepared by or are available to the Company, a copy of any unaudited interim financial statements of the Company for any period subsequent to the period covered by the most recent financial statements appearing in the Registration Statement, the Time of Sale Prospectus and the Prospectus.

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(k) No offering, pledge, sale, contract to sell, short sale or other disposition of any shares of Common Stock or other securities convertible into or exchangeable or exercisable for shares of Common Stock or derivative of Common Stock (or agreement for such) will be made for a period of 60 days after the date of the Prospectus, directly or indirectly, by the Company otherwise than hereunder or with the prior written consent of Goldman Sachs & Co. LLC, provided, however, that the Company may (i) effect the transactions contemplated hereby, (ii) issue Shares pursuant to the exercise of warrants outstanding as of the date hereof and described in the Registration Statement, the Time of Sale Prospectus and the Prospectus, but only if the holders of such Shares or warrants agree in writing with the Underwriters not to sell, offer, dispose of or otherwise transfer any such Shares or warrants during the 60-day restricted period, (iii) issue Shares or options to purchase Shares, or issue Shares upon exercise of options, pursuant to any stock option, stock bonus or other stock plan or arrangement described in the Registration Statement, the Time of Sale Prospectus and the Prospectus, but only if the holders of such Shares or options agree in writing with the Underwriters not to sell, offer, dispose of or otherwise transfer any such Shares or options during the 60-day restricted period and (iv) issue Shares or Related Securities in connection with a licensing arrangement, joint venture, acquisition or business combination or other collaboration or strategic transaction (including the filing of a registration statement on Form S-4 or other appropriate form with respect thereto); provided that, in the case of clause (iv), recipients of such Shares or Related Securities agree to be bound by the terms of the lockup letter in the form of Exhibit A hereto and the sum of the aggregate number of Shares or Related Securities so issued shall not exceed 5% of the total outstanding shares of Common Stock. For purposes of the foregoing, “Related Securities” shall mean any options or warrants or other rights to acquire Shares or any securities exchangeable or exercisable for or convertible into Shares, or to acquire other securities or rights ultimately exchangeable or exercisable for, or convertible into, Shares.

(l) The Company will use its best efforts to maintain the listing of the Common Stock on the NASDAQ Global Select Market.

(m) The Company has caused each officer and director and the specific stockholders set forth on Schedule IV hereto of the Company to execute and deliver to you, on or prior to the date of this agreement, a letter or letters, substantially in the form attached hereto as Exhibit A (the “Lockup Agreement”).

(n) The Company shall apply the net proceeds of its sale of the Shares as set forth in the Registration Statement, the Time of Sale Prospectus and the Prospectus.

(o) The Company shall not invest, or otherwise use the proceeds received by the Company from its sale of the Shares in such a manner as would require the Company or any of its subsidiaries to register as an investment company under the 1940 Act.

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(p) The Company will maintain a transfer agent and, if necessary under the jurisdiction of incorporation of the Company, a registrar for the Common Stock.

(q) The Company will not take, directly or indirectly, any action designed to cause or result in, or that has constituted or might reasonably be expected to constitute, the stabilization or manipulation of the price of any securities of the Company.

6. Covenants of the Underwriters. Each Underwriter severally covenants with the Company not to take any action that would result in the Company being required to file with the Commission under Rule 433(d) a free writing prospectus prepared by or on behalf of such Underwriter that otherwise would not be required to be filed by the Company thereunder, but for the action of the Underwriter.

7. Costs and Expenses. The Company will pay all costs, expenses and fees incident to the performance of the obligations of the Company under this Agreement, including, without limiting the generality of the foregoing, the following: (i) accounting fees of the Company; (ii) the fees and disbursements of counsel for the Company; (iii) all costs and expenses related to the transfer and delivery of the Shares to the Underwriters, including any transfer or other taxes payable thereon; (iv) any roadshow expenses, provided, however, that the Underwriters and the Company agree that the Underwriters shall be responsible for the payment of the Underwriters’ food and lodging expenses and fifty percent (50%) of the cost of aircraft and other transportation chartered in connection with the road show, to the extent applicable; (v) the cost of printing and delivering to, or as requested by, the Underwriters copies of the Registration Statement, Preliminary Prospectuses, the Issuer Free Writing Prospectuses, the Prospectus, this Agreement, the listing application, any Blue Sky survey, in each case, any supplements or amendments thereto; (vi) the filing fees of the Commission; (vii) the filing fees and expenses (including legal fees and disbursements of counsel for the Underwriters in an amount not to exceed $25,000) incident to securing any required review by FINRA of the terms of the sale of the Shares; (viii) all expenses and application fees related to the listing of the Shares on the NASDAQ Global Select Market; (ix) the cost of printing certificates, if any, representing the Shares; (x) the costs and charges of any transfer agent, registrar or depositary; (xi) the costs and expenses (including without limitation any damages or other amounts payable in connection with legal or contractual liability) associated with the reforming of any contracts for sale of the Shares made by the Underwriters caused by a breach of the representation in Section 1(b) hereof; and (xii) and the expenses, including the fees and disbursements of counsel for the Underwriters, incurred in connection with the qualification of the Shares under foreign or state securities or Blue Sky laws and the preparation, printing and distribution of a Blue Sky memorandum (including the related fees and expenses of counsel for the Underwriters) in an amount not to exceed $15,000. The Company shall not, however, be required to pay for any of the Underwriter’s expenses (other than those related to qualification under FINRA regulation and state securities or Blue Sky laws) except that, if this Agreement shall not be consummated because the conditions in Section 8 hereof are not satisfied, or because this Agreement is terminated by the Representatives pursuant to Section 12 hereof (other than subclauses (ii), (iii), (v) or (viii) of subsection (a) of Section 12), or by reason of any failure, refusal or inability on the part of the Company to perform any undertaking or

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satisfy any condition of this Agreement or to comply with any of the terms hereof on its part to be performed, unless such failure, refusal or inability is due primarily to the default or omission of any Underwriter, the Company shall reimburse the several Underwriters for reasonable out-of-pocket expenses, including fees and disbursements of counsel, reasonably incurred in connection with investigating, marketing and proposing to market the Shares or in contemplation of performing their obligations hereunder; but the Company shall not in any event be liable to any of the several Underwriters for damages on account of loss of anticipated profits from the sale by them of the Shares. Except as provided in this Section 7, the Underwriters shall pay their own expenses, including the fees and disbursements of their counsel.

8. Conditions of Obligations of the Underwriters. The several obligations of the Underwriters to purchase the Firm Shares on the Closing Date and the Additional Shares, if any, on the Option Closing Date are subject to the accuracy, as of the Applicable Time, the Closing Date or the Option Closing Date, as the case may be, of the representations and warranties of the Company contained herein, and to the performance by the Company of its covenants and obligations hereunder and to the following additional conditions:

(a) The Registration Statement and all post-effective amendments thereto shall have become and remain effective and the Prospectus and each Issuer Free Writing Prospectus required shall have been filed as required by Rules 424, 430A, 430B, 430C or 433 under the Securities Act, as applicable, within the time period prescribed by, and in compliance with, the rules and regulations of the Securities Act, and any request of the Commission for additional information (to be included in the Registration Statement or otherwise) shall have been disclosed to the Representatives and complied with to their reasonable satisfaction. No stop order suspending the effectiveness of the Registration Statement, as amended from time to time, shall have been issued and no proceedings for that purpose or pursuant to Section 8A under the Securities Act shall have been taken or, to the knowledge of the Company, shall be contemplated or threatened by the Commission and no injunction, restraining order or order of any nature by a federal or state court of competent jurisdiction shall have been issued as of the Closing Date which would prevent the issuance of the Shares.

(b) The Representatives shall have received on the Closing Date or the Option Closing Date, as the case may be, the opinion and negative assurance letter of Cooley LLP, counsel for the Company, dated the Closing Date or the Option Closing Date, as the case may be, addressed to the Underwriters (and stating that it may be relied upon by counsel to the Underwriters) substantially in the form of Annex A hereto.

(c) The Representatives shall have received on the Closing Date or the Option Closing Date, as the case may be, the opinion of Cooley LLP, intellectual property counsel for the Company, dated the Closing Date or the Option Closing Date, as the case may be, addressed to the Underwriters (and stating that it may be relied upon by counsel to the Underwriters) substantially in the form of Annex B hereto.

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(d) The Representatives shall have received from Goodwin Procter LLP, counsel for the Underwriters, an opinion and the negative assurance letter, dated the Closing Date or the Option Closing Date, as the case may be, with respect to such matters as the Representatives may reasonably request, and such counsel shall have received such documents and information as they may reasonably request to enable them to pass upon such matters.

(e) The Representatives shall have received, on each of the date hereof, the Closing Date and, if applicable, the Option Closing Date, a letter dated the date hereof, the Closing Date or the Option Closing Date, as the case may be, in form and substance satisfactory to them, of Deloitte & Touche LLP confirming that they are an independent registered public accounting firm with respect to the Company and the subsidiaries within the meaning of the Securities Act and the applicable rules and regulations and the PCAOB and stating that in their opinion the financial statements and schedules examined by them and included in the Registration Statement, the Time of Sale Prospectus and the Prospectus comply in form in all material respects with the applicable accounting requirements of the Securities Act and the related rules and regulations; and containing such other statements and information as is ordinarily included in accountants’ “comfort letters” to underwriters with respect to the financial statements and certain financial and statistical information contained in the Registration Statement, the Time of Sale Prospectus and the Prospectus.

(f) The Representatives shall have received on the Closing Date and, if applicable, the Option Closing Date, as the case may be, a certificate or certificates of the Chief Executive Officer and the Chief Financial Officer of the Company to the effect that, as of the Closing Date or the Option Closing Date, as the case may be, each of them severally represents as follows:

(i) The Registration Statement is effective under the Securities Act and no stop order suspending the effectiveness of the Registration Statement or no order preventing or suspending the use of any Preliminary Prospectus, any Issuer Free Writing Prospectus or the Prospectus has been issued, and no proceedings for such purpose or pursuant to Section 8A of the Securities Act have been taken or are, to his or her knowledge, contemplated or threatened by the Commission;

(ii) The representations and warranties of the Company contained in Section 1 hereof are true and correct as of the Closing Date or the Option Closing Date, as the case may be;

(iii) All filings required to have been made pursuant to Rules 424, 430A, 430B or 430C under the Securities Act have been made as and when required by such rules;

(iv) He or she has carefully examined the Time of Sale Prospectus and any individual Limited Use Free Writing Prospectus and, in his or her opinion, as of the Applicable Time, the statements contained in the Time of Sale Prospectus and any individual Limited Use Free Writing Prospectus did not contain any untrue statement of a material fact, and such Time of Sale Prospectus and any individual Limited Use Free Writing Prospectus, when considered together with the Time of Sale Prospectus, did not omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading;

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(v) He or she has carefully examined the Registration Statement and, in his or her opinion, as of the effective date of the Registration Statement, the Registration Statement and any amendments thereto did not contain any untrue statement of a material fact and did not omit to state a material fact necessary in order to make the statements therein not misleading, and since the effective date of the Registration Statement, no event has occurred which should have been set forth in a supplement to or an amendment of the Prospectus which has not been so set forth in such supplement or amendment; and

(vi) He or she has carefully examined the Prospectus and, in his or her opinion, as of its date and the Closing Date or the Option Closing Date, as the case may be, the Prospectus and any amendments and supplements thereto did not contain any untrue statement of a material fact and did not omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.

(g) Since the respective dates as of which information is given in the Registration Statement, the Time of Sale Prospectus and Prospectus, there has not been a Material Adverse Effect, whether or not arising in the ordinary course of business; subsequent to the execution and delivery of this Agreement and prior to the Closing Date, there shall not have occurred any downgrading, nor shall any notice have been given of any intended or potential downgrading or of any review for a possible change that does not indicate the direction of the possible change, in the rating accorded any of the securities of the Company or any of its subsidiaries by any “nationally recognized statistical rating organization,” as such term is defined in Section 3(a)(62) of the Exchange Act, and there shall not have occurred any change, or any development involving a prospective change, in the condition, financial or otherwise, or in the earnings, business or operations of the Company and its subsidiaries, taken as a whole, from that set forth in the Time of Sale Prospectus that, in your judgment, is material and adverse and that makes it, in your judgment, impracticable to market the Shares on the terms and in the manner contemplated in the Time of Sale Prospectus.

(h) The Company shall have furnished to the Representatives such further certificates and documents confirming the representations and warranties, covenants and conditions contained herein and related matters as the Representatives may reasonably have requested.

(i) The Firm Shares and Additional Shares, if any, have been approved for quotation upon notice of issuance on the NASDAQ Global Select Market.

(j) The Lockup Agreements described in Section 5(m) hereof are in full force and effect.

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(k) No action shall have been taken and no statute, rule, regulation or order shall have been enacted, adopted or issued by any federal, state or foreign governmental or regulatory authority that would, as of the Closing Date or the Option Closing Date, as the case may be, prevent the issuance or sale of the Shares by the Company; and no injunction or order of any federal, state or foreign court shall have been issued that would, as of the Closing Date or the Option Closing Date, as the case may be, prevent the issuance or sale of the Shares by the Company.

The opinions and certificates mentioned in this Agreement shall be deemed to be in compliance with the provisions hereof only if they are in all material respects satisfactory to the Representatives and to Goodwin Procter LLP, counsel for the Underwriters.

If any of the conditions hereinabove provided for in this Section 8 shall not have been fulfilled when and as required by this Agreement to be fulfilled, the obligations of the Underwriters hereunder may be terminated by the Representatives by notifying the Company of such termination in writing or by telegram at or prior to the Closing Date or the Option Closing Date, as the case may be.

In such event, the Company and the Underwriters shall not be under any obligation to each other (except to the extent provided in Sections 7 and 9 hereof).

9. Indemnity and Contribution.

(a) The Company agrees:

(i) to indemnify and hold harmless each Underwriter, the directors, officers and employees of each Underwriter and each person, if any, who controls any Underwriter within the meaning of either Section 15 of the Securities Act or Section 20 of the Exchange Act, and each of their respective affiliates, against any losses, claims, damages or liabilities to which such Underwriter or any such controlling person may become subject under the Securities Act or otherwise, insofar as such losses, claims, damages or liabilities (or actions or proceedings in respect thereof) arise out of or are based upon (i) any untrue statement or alleged untrue statement of any material fact contained in the Registration Statement, any Preliminary Prospectus, any Issuer Free Writing Prospectus, the Prospectus or any amendment or supplement thereto, or any road show as defined in Rule 433(h) under the Securities Act (a “road show”), (ii) with respect to the Registration Statement or any amendment or supplement thereto, the omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading or (iii) with respect to any Preliminary Prospectus, any Issuer Free Writing Prospectus, or road show, the Prospectus or any amendment or supplement thereto, the omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading in the light of the circumstances under which they were made; provided, however, that the Company will not be liable in any such case to the extent that any such loss, claim, damage or liability arises out of or is based upon an untrue statement or alleged untrue statement, or omission or alleged omission made in the Registration Statement, any Preliminary Prospectus, any Issuer Free Writing

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Prospectus, the Prospectus, or such amendment or supplement, in reliance upon and in conformity with written information furnished to the Company by or through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 14 hereof; and

(ii) to reimburse each Underwriter, each Underwriters’ directors, officers, employees and affiliates, and each such controlling person upon demand for any legal or other out-of-pocket expenses reasonably incurred by such Underwriter or such controlling person in connection with investigating or defending any such loss, claim, damage or liability, action or proceeding or in responding to a subpoena or governmental inquiry related to the offering of the Shares, whether or not such Underwriter or controlling person is a party to any action or proceeding. In the event that it is finally judicially determined that the Underwriters were not entitled to receive payments for legal and other expenses pursuant to this subparagraph, the Underwriters will promptly return all sums that had been advanced pursuant hereto.

(b) Each Underwriter severally and not jointly will indemnify and hold harmless the Company, each of its directors, each of its officers who have signed the Registration Statement and each person, if any, who controls the Company within the meaning of the Securities Act, against any losses, claims, damages or liabilities to which the Company or any such director, officer, or controlling person may become subject under the Securities Act or otherwise, insofar as such losses, claims, damages or liabilities (or actions or proceedings in respect thereof) arise out of or are based upon (i) any untrue statement or alleged untrue statement of any material fact contained in the Registration Statement, any Preliminary Prospectus, any Issuer Free Writing Prospectus, the Prospectus or any amendment or supplement thereto, (ii) with respect to the Registration Statement or any amendment or supplement thereto, the omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading or (iii) with respect to any Preliminary Prospectus, any Issuer Free Writing Prospectus, the Prospectus or any amendment or supplement thereto, the omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading in the light of the circumstances under which they were made; and will reimburse any legal or other expenses reasonably incurred by the Company or any such director, officer or controlling person in connection with investigating or defending any such loss, claim, damage, liability, action or proceeding; provided, however, that each Underwriter will be liable in each case to the extent, but only to the extent, that such untrue statement or alleged untrue statement or omission or alleged omission has been made in the Registration Statement, any Preliminary Prospectus, any Issuer Free Writing Prospectus, the Prospectus or such amendment or supplement, in reliance upon and in conformity with written information furnished to the Company by or through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 14 hereof. This indemnity agreement will be in addition to any liability which such Underwriter may otherwise have.

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(c) In case any proceeding (including any governmental investigation) shall be instituted involving any person in respect of which indemnity may be sought pursuant to this Section 9, such person (the “indemnified party”) shall promptly notify the person against whom such indemnity may be sought (the “indemnifying party”) in writing. No indemnification provided for in Section 9(a) or (b) hereof shall be available to any party who shall fail to give notice as provided in this Section 9(c) if the party to whom notice was not given was unaware of the proceeding to which such notice would have related and was materially prejudiced (through the forfeiture of substantive rights or defenses) by the failure to give such notice, but the failure to give such notice shall not relieve the indemnifying party or parties from any liability which it or they may have to the indemnified party for contribution or otherwise than on account of the provisions of Section 9(a) or (b) hereof. In case any such proceeding shall be brought against any indemnified party and it shall notify the indemnifying party of the commencement thereof, the indemnifying party shall be entitled to participate therein and, to the extent that it shall wish, jointly with any other indemnifying party similarly notified, to assume the defense thereof, with counsel satisfactory to such indemnified party and shall pay as incurred the fees and disbursements of such counsel related to such proceeding. In any such proceeding, any indemnified party shall have the right to retain its own counsel at its own expense. Notwithstanding the foregoing, the indemnifying party shall pay as incurred (or within 30 days of presentation) the fees and expenses of the counsel retained by the indemnified party in the event (i) the indemnifying party and the indemnified party shall have mutually agreed to the retention of such counsel, (ii) the named parties to any such proceeding (including any impleaded parties) include both the indemnifying party and the indemnified party and representation of both parties by the same counsel would be inappropriate due to actual or potential differing interests between them or (iii) the indemnifying party shall have failed to assume the defense and employ counsel acceptable to the indemnified party within a reasonable period of time after notice of commencement of the action. Such firm shall be designated in writing by you in the case of parties indemnified pursuant to Section 9(a) or (b) hereof and by the Company in the case of parties indemnified pursuant to Section 9(b) hereof. The indemnifying party shall not be liable for any settlement of any proceeding effected without its written consent but if settled with such consent or if there be a final judgment for the plaintiff, the indemnifying party agrees to indemnify the indemnified party from and against any loss or liability by reason of such settlement or judgment. In addition, the indemnifying party will not, without the prior written consent of the indemnified party, settle or compromise or consent to the entry of any judgment in any pending or threatened claim, action or proceeding of which indemnification may be sought hereunder (whether or not any indemnified party is an actual or potential party to such claim, action or proceeding) unless such settlement, compromise or consent (i) includes an unconditional release of each indemnified party from all liability arising out of such claim, action or proceeding and (ii) does not include a statement as to or an admission of fault, culpability or a failure to act by or on behalf of any indemnified party. If at any time an indemnified party shall have requested an indemnifying party to reimburse the indemnified party for fees and expenses of counsel, such indemnifying party agrees that it shall be liable for any settlement of any proceeding effected without its written consent if (i) such settlement is entered into more than 45 days after receipt by such indemnifying party of the aforesaid request, (ii) such indemnifying party shall have received notice of the terms of such settlement at least 30 days prior to such settlement being entered into and (iii) such indemnifying party shall not have reimbursed such indemnified party in accordance with such request prior to the date of such settlement.

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(d) To the extent the indemnification provided for in this Section 9 is unavailable to or insufficient to hold harmless an indemnified party under Section 9(a) or (b) hereof in respect of any losses, claims, damages or liabilities (or actions or proceedings in respect thereof) referred to therein, then each indemnifying party shall contribute to the amount paid or payable by such indemnified party as a result of such losses, claims, damages or liabilities (or actions or proceedings in respect thereof) in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriters on the other from the offering of the Shares. If, however, the allocation provided by the immediately preceding sentence is not permitted by applicable law, then each indemnifying party shall contribute to such amount paid or payable by such indemnified party in such proportion as is appropriate to reflect not only such relative benefits but also the relative fault of the Company on the one hand and the Underwriters on the other in connection with the statements or omissions which resulted in such losses, claims, damages or liabilities (or actions or proceedings in respect thereof), as well as any other relevant equitable considerations. The relative benefits received by the Company on the one hand and the Underwriters on the other shall be deemed to be in the same proportion as the net proceeds from the offering (before deducting expenses) received by the Company bear to the total underwriting discounts and commissions received by the Underwriters, in each case as set forth in the table on the cover page of the Prospectus. The relative fault shall be determined by reference to, among other things, whether the untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information supplied by the Company on the one hand or the Underwriters on the other and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission.

The Company and the Underwriters agree that it would not be just and equitable if contributions pursuant to this Section 9(d) were determined by pro rata allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation which does not take account of the equitable considerations referred to above in this Section 9(d). The amount paid or payable by an indemnified party as a result of the losses, claims, damages or liabilities (or actions or proceedings in respect thereof) referred to above in this Section 9(d) shall be deemed to include any legal or other expenses reasonably incurred by such indemnified party in connection with investigating or defending any such action or claim. Notwithstanding the provisions of this Section 9(d), (i) no Underwriter shall be required to contribute any amount in excess of the underwriting discounts and commissions applicable to the Shares purchased by such Underwriter and (ii) no person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Securities Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation. The Underwriters’ obligations in this Section 9(d) to contribute are several in proportion to their respective underwriting obligations and not joint.

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(e) In any proceeding relating to the Registration Statement, any Preliminary Prospectus, any Issuer Free Writing Prospectus, the Prospectus or any supplement or amendment thereto, each party against whom contribution may be sought under this Section 9 hereby consents to the exclusive jurisdiction of (i) the federal courts of the United States of America located in the City and County of New York, Borough of Manhattan and (ii) the courts of the State of New York located in the City and County of New York, Borough of Manhattan (collectively, the “Specified Courts”), agrees that process issuing from such courts may be served upon it by any other contributing party and consents to the service of such process and agrees that any other contributing party may join it as an additional defendant in any such proceeding in which such other contributing party is a party. The Company irrevocably appoints Cooley LLP as its agent to receive service of process or other legal summons for purposes of any such suit, action or proceeding that may be instituted in any state or federal court in the City and County of New York.

(f) Any losses, claims, damages, liabilities or expenses for which an indemnified party is entitled to indemnification or contribution under this Section 9 shall be paid by the indemnifying party to the indemnified party as such losses, claims, damages, liabilities or expenses are incurred. The indemnity and contribution agreements contained in this Section 9 and the representations and warranties of the Company set forth in this Agreement shall remain operative and in full force and effect, regardless of (i) any investigation made by or on behalf of any Underwriter, its directors, officers, employees or any person controlling any Underwriter, the Company, its directors, officers, employees or any persons controlling the Company, (ii) acceptance of any Shares and payment therefor hereunder, and (iii) any termination of this Agreement. A successor to any Underwriter, its directors or officers or any person controlling any Underwriter, or to the Company, its directors, officers, employees or any person controlling the Company, shall be entitled to the benefits of the indemnity, contribution and reimbursement agreements contained in this Section 9.

10. Defaulting Underwriters. If on the Closing Date or the Option Closing Date, as the case may be, any Underwriter shall fail to purchase and pay for the portion of the Shares which such Underwriter has agreed to purchase and pay for on such date (otherwise than by reason of any default on the part of the Company), you, as Representatives of the Underwriters, shall use your reasonable efforts to procure within 36 hours thereafter one or more of the other Underwriters, or any others, to purchase from the Company such amounts as may be agreed upon and upon the terms set forth herein, the Shares which the defaulting Underwriter or Underwriters failed to purchase. If during such 36 hours you, as such Representatives, shall not have procured such other Underwriters, or any others, to purchase the Shares agreed to be purchased by the defaulting Underwriter or Underwriters, then (a) if the aggregate number of shares with respect to which such default shall occur does not exceed 10% of the Shares to be purchased on the Closing Date or the Option Closing date, as the case may be, the other Underwriters shall be obligated, severally, in proportion to the respective numbers of Shares which they are obligated to purchase hereunder, to purchase the Shares which such defaulting Underwriter or Underwriters failed to purchase, or (b) if the aggregate number of shares of Shares with respect to which such default shall occur exceeds 10% of the Shares to be purchased on the Closing Date or the Option Closing Date, as the case may be, the Company or you as the Representatives of the Underwriters will have the right, by written notice given within the next 36-hour period to the parties to this

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Agreement, to terminate this Agreement without liability on the part of the non-defaulting Underwriters or of the Company except to the extent provided in Sections 7 and 9 hereof. In the event of a default by any Underwriter or Underwriters, as set forth in this Section 10, the Closing Date or Option Closing Date, as the case may be, may be postponed for such period, not exceeding seven days, as you, as Representatives, may determine in order that the required changes in the Registration Statement, the Time of Sale Prospectus or in the Prospectus or in any other documents or arrangements may be effected. The term “Underwriter” includes any person substituted for a defaulting Underwriter. Any action taken under this Section 10 shall not relieve any defaulting Underwriter from liability in respect of any default of such Underwriter under this Agreement.

11. Notices. All communications hereunder shall be in writing and, except as otherwise provided herein, will be mailed, delivered, telecopied or telegraphed and confirmed as follows: if to the Underwriters, to Goldman Sachs & Co. LLC, 200 West Street, New York, New York 10282, Attention: Registration Department; Citigroup Global Markets Inc., 388 Greenwich Street, New York, New York 10013, Attention: General Counsel; and Cowen and Company, LLC, 599 Lexington Avenue, New York, New York, 10022, Attention: General Counsel, in each case with a copy to Goodwin Procter LLP, 620 Eighth Avenue, New York, New York 10018, Attention: Edwin M. O’Connor; if to the Company, to Syndax Pharmaceuticals, Inc., 35 Gatehouse Drive, Building D, Floor 3, Waltham, Massachusetts 02451, Attention: Luke Albrecht, fax number: (781) 419-1420, with a copy to Cooley LLP, 3175 Hanover Street, Palo Alto, California 94304, Attention: Laura Berezin.

12. Termination. This Agreement may be terminated by you by notice to the Company (a) at any time prior to the Closing Date or any Option Closing Date (if different from the Closing Date and then only as to Additional Shares) if any of the following has occurred: (i) since the respective dates as of which information is given in the Registration Statement, the Time of Sale Prospectus and the Prospectus, any material adverse change or any development involving a prospective material adverse change in or affecting the earnings, business, management, properties, assets, rights, operations, condition (financial or otherwise) or prospects of the Company and the subsidiaries taken as a whole, whether or not arising in the ordinary course of business; (ii) any outbreak or escalation of hostilities or declaration of war or national emergency or other national or international calamity or crisis (including, without limitation, an act of terrorism) or change in economic or political conditions if the effect of such outbreak, escalation, declaration, emergency, calamity, crisis or change on the financial markets of the United States would, in your judgment, materially impair the investment quality of the Shares; (iii) suspension of trading in securities generally on the New York Stock Exchange, the American Stock Exchange or the NASDAQ Stock Market or limitation on prices (other than limitations on hours or numbers of days of trading) for securities on any such exchange; (iv) the enactment, publication, decree or other promulgation of any statute, regulation, rule or order of any court or other governmental authority which in your opinion materially and adversely affects or may materially and adversely affect the business or operations of the Company; (v) the declaration of a banking moratorium by the United States or New York State and other jurisdictions as applicable authorities; (vi)

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any downgrading, or placement on any watch list for possible downgrading, in the rating of any of the Company’s debt securities or preferred stock by any “nationally recognized statistical rating organization” (within the meaning of Rule 15c3-1(c)(2)(vi)(F) under the Exchange Act) or any public announcement by such organization that it has under surveillance or review, or has changed its outlook with respect to, its rating of any such debt securities or preferred stock (other than an announcement with positive implications of a possible upgrading); (vii) the suspension of trading of the Company’s common stock by the NASDAQ Global Select Market, the Commission or any other governmental authority; or (viii) the taking of any action by any governmental body or agency in respect of its monetary or fiscal affairs which in your opinion has a material adverse effect on the securities markets in the United States; or (b) as provided in Sections 8 and 10 of this Agreement.

13. Successors. This Agreement has been and is made solely for the benefit of the Underwriters and the Company and their respective successors, executors, administrators, heirs and assigns, and the officers, directors and controlling persons referred to herein, and no other person will have any right or obligation hereunder. No purchaser of any of the Shares from any Underwriter shall be deemed a successor or assign merely because of such purchase.

14. Information Provided By Underwriters. The Company and the Underwriters acknowledge and agree that the only information furnished or to be furnished by any Underwriter to the Company for inclusion in the Registration Statement, any Preliminary Prospectus, any Issuer Free Writing Prospectus, or the Prospectus consists of the information set forth in the third and twelfth paragraphs under the caption “Underwriters” in the Prospectus.

15. Entire Agreement.

(a) This Agreement, together with any contemporaneous written agreements and any prior written agreements (to the extent not superseded by this Agreement) that relate to the offering of the Shares, represents the entire agreement between the Company and the Underwriters with respect to the preparation of any preliminary prospectus, the Time of Sale Prospectus, the Prospectus, the conduct of the offering, and the purchase and sale of the Shares.

(b) The Company acknowledges that in connection with the offering of the Shares: (i) the Underwriters have acted at arms length, are not agents of, and owe no fiduciary duties to, the Company or any other person, (ii) the Underwriters owe the Company only those duties and obligations set forth in this Agreement and prior written agreements (to the extent not superseded by this Agreement), if any, and (iii) the Underwriters may have interests that differ from those of the Company. The Company waives to the full extent permitted by applicable law any claims it may have against the Underwriters arising from an alleged breach of fiduciary duty in connection with the offering of the Shares.

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16. Counterparts. This Agreement may be signed in two or more counterparts, each of which shall be an original, with the same effect as if the signatures thereto and hereto were upon the same instrument.

17. Applicable Law. This Agreement shall be governed by, and construed in accordance with, the law of the State of New York, including, without limitation, Section 5-1401 of the New York General Obligations Law.

18. Headings. The headings of the sections of this Agreement have been inserted for convenience of reference only and shall not be deemed a part of this Agreement.

19. Miscellaneous.

(a) The reimbursement, indemnification and contribution agreements contained in this Agreement and the representations, warranties and covenants in this Agreement shall remain in full force and effect regardless of (a) any termination of this Agreement, (b) any investigation made by or on behalf of any Underwriter or controlling person thereof, or by or on behalf of the Company or its directors or officers, and (c) delivery of and payment for the Shares under this Agreement.

(b) The Company acknowledges and agrees that each Underwriter in providing investment banking services to the Company in connection with the offering, including in acting pursuant to the terms of this Agreement, has acted and is acting as an independent contractor and not as a fiduciary and the Company does not intend such Underwriter to act in any capacity other than as an independent contractor, including as a fiduciary or in any other position of higher trust. Additionally, neither the Representatives nor any other Underwriter is advising the Company or any other person as to any legal, tax, investment, accounting or regulatory matters in any jurisdiction. The Company shall consult with their own advisors concerning such matters and shall be responsible for making their own independent investigation and appraisal of the transactions contemplated hereby, and the Underwriters shall have no responsibility or liability to the Company with respect thereto. Any review by the Underwriters of the Company, the transactions contemplated hereby or other matters relating to such transactions will be performed solely for the benefit of the Underwriters and shall not be on behalf of the Company. The Company agrees and acknowledges that the Underwriters have not provided any recommendation or investment advice with respect to the transactions contemplated herein.

(c) The Underwriters, on the one hand, and the Company (on its own behalf and, to the extent permitted by law, on behalf of its stockholders), on the other hand, waive any right to trial by jury in any action, claim, suit or proceeding with respect to your engagement as underwriter or your role in connection herewith.

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20. Recognition of the U.S. Special Resolution Regimes.

(a) In the event that any Underwriter is a Covered Entity and becomes subject to a proceeding under a U.S. Special Resolution Regime, the transfer from such Underwriter of this Agreement, and any interest and obligation in or under this Agreement, will be effective to the same extent as the transfer would be effective under the U.S. Special Resolution Regime if this Agreement, and any such interest and obligation, were governed by the laws of the United States or a state of the United States.

(b) In the event that any Underwriter is a Covered Entity or a BHC Act Affiliate of such Underwriter and becomes subject to a proceeding under a U.S. Special Resolution Regime, Default Rights under this Agreement that may be exercised against such Underwriter are permitted to be exercised to no greater extent than such Default Rights could be exercised under the U.S. Special Resolution Regime if this Agreement were governed by the laws of the United States or a state of the United States.

For purposes of this Section 20:

“BHC Act Affiliate” has the meaning assigned to the term “affiliate” in, and shall be interpreted in accordance with, 12 U.S.C. § 1841(k).

“Covered Entity” means any of the following: (i) a “covered entity” as that term is defined in, and interpreted in accordance with, 12 C.F.R. § 252.82(b); (ii) a “covered bank” as that term is defined in, and interpreted in accordance with, 12 C.F.R. §47.3(b); or (iii) a “covered FSI” as that term is defined in, and interpreted in accordance with, 12 C.F.R. §382.2(b).

“Default Right” has the meaning assigned to that term in, and shall be interpreted in accordance with, 12 C.F.R. §§ 252.81, 47.2 or 382.1, as applicable.

“U.S. Special Resolution Regime” means each of (i) the Federal Deposit Insurance Act and the regulations promulgated thereunder and (ii) Title II of the Dodd-Frank Wall Street Reform and Consumer Protection Act and the regulations promulgated thereunder.

[Signature Page Follows]

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[Signature Page – Underwriting Agreement]

SCHEDULE I

I-1

SCHEDULE II

Time of Sale Prospectus

Preliminary Prospectus issued December 7, 2020

II-1

SCHEDULE III

List of Subsidiaries

III-1

SCHEDULE IV

Stockholders Subject to Lockup

Michael A. Metzger

Daphne Karydas

Michael L. Meyers, M.D., Ph.D.

Peter Ordentlich, Ph.D.

Briggs W. Morrison, M.D.

Dennis G. Podlesak

Keith A. Katkin

Jennifer Jarrett

Fabrice Egros, Ph.D.

Pierre Legault

William Meury

IV-1

EXHIBIT A

FORM OF LOCK-UP LETTER

December [●], 2020                

Syndax Pharmaceuticals, Inc.

Goldman Sachs & Co. LLC

Citigroup Global Markets, Inc.

Cowen and Company, LLC

c/o Goldman Sachs & Co. LLC

200 West Street

New York, New York 10282-2198

c/o Citigroup Global Markets Inc.

388 Greenwich Street

New York, New York 10013

c/o Cowen and Company, LLC

599 Lexington Avenue

New York, New York 10022

Ladies and Gentlemen:

The undersigned understands that Goldman Sachs & Co., Citigroup Global Markets Inc. and Cowen and Company, LLC, as representatives (the “Representatives”) of the several underwriters (the “Underwriters”), propose to enter into an Underwriting Agreement (the “Underwriting Agreement”) with Syndax Pharmaceuticals, Inc. (the “Company”) relating to the public offering by the Company of an unspecified number of shares of common stock, par value $0.0001 per share (the “Common Stock”), of the Company (the “Offering”).

To induce the Underwriters that may participate in the Offering to continue their efforts in connection with the Offering, the undersigned agrees that, without the prior written consent of Goldman Sachs & Co. LLC on behalf of the Underwriters, the undersigned will not, directly or indirectly, offer, sell, pledge, contract to sell (including any short sale), grant any option to purchase or otherwise transfer or dispose of any shares of Common Stock (including, without limitation, shares of Common Stock which

may be deemed to be beneficially owned by the undersigned currently or hereafter in accordance with the rules and regulations of the Securities and Exchange Commission (the “Commission”), shares of Common Stock which may be issued upon exercise of a stock option or warrant and any other security convertible into or exchangeable for Common Stock), enter into any Hedging Transaction (as defined below) relating to the Common Stock (each of the foregoing referred to as a “Disposition”), or publicly announce any intention to do so, during the period commencing on the date hereof and continuing until, and including, the date that is sixty (60) days after the date of the final prospectus relating to the Offering (the “Lock-Up Period”). The foregoing restriction is expressly intended to preclude the undersigned from engaging in any Hedging Transaction or other transaction which is designed to or reasonably expected to lead to or result in a Disposition during the Lock-Up Period even if the securities would be disposed of by someone other than the undersigned. “Hedging Transaction” means any short sale (whether or not against the box) or any purchase, sale or grant of any right (including, without limitation, any put or call option) with respect to any security (other than a broad-based market basket or index) that includes, relates to or derives any significant part of its value from the Common Stock.

The foregoing restrictions shall not apply to the transfer of any or all of the shares of Common Stock or other Company securities by the undersigned if the transfer does not trigger any filing or reporting requirement or obligation or result in any other voluntary or mandatory public disclosure under Section 16(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the transfer is (i) by gift, will or intestacy, (ii) to a trust whose beneficiaries consist exclusively of one or more of the undersigned and/or the family member(s) of the undersigned, (iii) a distribution to partners, members or shareholders of the undersigned, or to any corporation, partnership or limited liability company that is an affiliate (within the meaning set forth in Rule 405 as promulgated by the Securities and Exchange Commission under the Securities Act of 1933, as amended) of the undersigned, or (iv) to the Company upon the exercise of options to cover tax withholding obligations in connection with such exercise or for the primary purpose of paying the exercise price of options or warrants to acquire shares of Common Stock in each case pursuant to a stock option, stock bonus or other stock plan, warrant agreement or other arrangement existing as of the date hereof and any shares acquired shall remain subject to this Lock-Up Agreement; provided, however, it shall be a condition to the transfer that the transferee execute an agreement stating that the transferee is receiving and holding the securities subject to the provisions of this Lock-Up Agreement. In addition, the undersigned may enter into any plan designed to satisfy the requirements of Rule 10b5-1 under the Exchange Act (a “10b5-1 Plan”) (other than the entry into such a plan in such a manner as to allow the sale of shares of Common Stock or other Company securities, in each case, within the Lock-Up Period); provided however, no public announcement or filing under the Exchange Act regarding the establishment of such 10b5-1 Plan shall be required or made during the Lock-Up Period.

For the avoidance of doubt, the foregoing restrictions shall not apply to, and nothing in this Lock-Up Agreement prohibits the undersigned (or any family member of the undersigned) from (i) exercising any options, warrants or other rights to purchase shares of Common Stock pursuant to any stock option, stock bonus or other stock plan or

2

any other arrangement existing as of the date hereof (which exercises may be effected on a cashless basis to the extent the instruments representing such options, warrants or other rights permit exercises on a cashless basis) or (ii) the grant by the Company of stock options or other stock-based awards to the undersigned pursuant to any stock option, stock bonus or other stock plan, warrant agreement or other arrangement existing as of the date hereof; provided, however, that in any such case, any shares of Common Stock or other Company securities acquired shall remain subject to this Lock-Up Agreement; and provided further, that (A) any filing under Section 16 of the Exchange Act made during the Lock-Up Period shall clearly indicate in the footnotes thereto that (1) the filing relates to the circumstances described above and (2) the shares Common Stock continue to be subject to the restrictions on transfer set forth in this Letter Agreement and (B) the undersigned does not otherwise voluntarily effect any other public filings or reports regarding such exercise during the Lock-Up Period.

The undersigned agrees that the Company may, and that the undersigned authorizes the Company to, (i) with respect to any shares of Common Stock or other Company securities for which the undersigned is the record holder, cause the transfer agent for the Company to note stop transfer instructions with respect to such securities on the transfer books and records of the Company and (ii) with respect to any shares of Common Stock or other Company securities for which the undersigned is the beneficial holder but not the record holder, cause the record holder of such securities to cause the transfer agent for the Company to note stop transfer instructions with respect to such securities on the transfer books and records of the Company.

In addition, the undersigned hereby waives any and all notice requirements and rights with respect to registration of securities pursuant to any agreement, understanding or otherwise setting forth the terms of any security of the Company held by the undersigned, including any registration rights agreement to which the undersigned and the Company may be party; provided that such waiver shall apply only to the proposed Offering, and any other action taken by the Company in connection with the proposed Offering.

The undersigned hereby agrees that, to the extent that the terms of this Lock-Up Agreement conflict with or are in any way inconsistent with any registration rights agreement to which the undersigned and the Company may be a party, this Lock-Up Agreement supersedes such registration rights agreement.

The undersigned hereby represents and warrants that the undersigned has full power and authority to enter into this Lock-Up Agreement. All authority herein conferred or agreed to be conferred shall survive the death or incapacity of the undersigned and any obligations of the undersigned shall be binding upon the heirs, personal representatives, successors and assigns of the undersigned.

Notwithstanding anything herein to the contrary, if (i) the Company notifies the Representatives in writing that it does not intend to proceed with the Offering prior to the execution of the Underwriting Agreement, (ii) the Underwriting Agreement (other than the provisions thereof which survive termination) is terminated for any reason prior to payment for and delivery of the shares of Common Stock to be sold thereunder or (iii) the closing of the Offering has not occurred prior to December 31, 2020, this Lock-Up Agreement shall be of no further force or effect.

3

The undersigned acknowledges and agrees that the Underwriters have not provided any recommendation or investment advice nor have the Underwriters solicited any action from the undersigned with respect to the Public Offering of the Shares and the undersigned has consulted their own legal, accounting, financial, regulatory and tax advisors to the extent deemed appropriate. The undersigned further acknowledges and agrees that, although the Underwriters may provide certain Regulation Best Interest and Form CRS disclosures or other related documentation to you in connection with the Public Offering, the Underwriters are not making a recommendation to you to participate in the Public Offering or sell any Shares at the price determined in the Public Offering, and nothing set forth in such disclosures or documentation is intended to suggest that any Underwriter is making such a recommendation.

The undersigned understands that the Company and the Underwriters are relying upon this Lock-Up Agreement in proceeding toward consummation of the offering. The undersigned further understands that this Lock-Up Agreement is irrevocable and shall be binding upon the undersigned’s heirs, legal representatives, successors, and assigns. This Lock-Up Agreement may be delivered via facsimile, electronic mail (including pdf or any electronic signature complying with the U.S. federal ESIGN Act of 2000, e.g., www.docusign.com or www.echosign.com) or other transmission method and any counterpart so delivered shall be deemed to have been duly and validly delivered and be valid and effective for all purposes.

This Lock-Up Agreement shall be governed by, and construed in accordance with, the law of the State of New York, including, without limitation, Section 5-1401 of the New York General Obligations Law.

4

ANNEX A

FORM OF COOLEY OPINION

ANNEX B

FORM OF COOLEY INTELLECTUAL PROPERTY OPINION

Exhibit 5.1

Laura A. Berezin

+1 650 843 5128

lberezin@cooley.com

December 9, 2020

Syndax Pharmaceuticals, Inc.

Building D, Floor 3

35 Gatehouse Drive

Waltham, Massachusetts 02451

Ladies and Gentlemen:

You have requested our opinion, as counsel to Syndax Pharmaceuticals, Inc., a Delaware corporation (the “Company”), with respect to certain matters in connection with the offering by the Company of up to 6,250,000 shares of its common stock, par value $0.0001 (the “Shares”), including up to 815,217 Shares that may be sold pursuant to the exercise of an option to purchase additional Shares, pursuant to a Registration Statement on Form S-3 (Registration Statement No. 333-233564) (the “Registration Statement”), filed with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act”), the prospectus included in the Registration Statement (the “Base Prospectus”), and the prospectus supplement, dated December 8, 2020, and filed with the Commission pursuant to Rule 424(b) of the Rules and Regulations of the Act (together with the Base Prospectus, the “Prospectus”).

In connection with this opinion, we have examined and relied upon the Registration Statement, the Prospectus, the Company’s Amended and Restated Certificate of Incorporation and Amended and Restated Bylaws, each as currently in effect, and originals or copies certified to our satisfaction of such records, documents, certificates, memoranda and other instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below. In rendering this opinion, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to originals of all documents submitted to us as copies; the accuracy, completeness and authenticity of certificates of public officials, and the due authorization, execution and delivery of all documents by all persons other than the Company where authorization, execution and delivery are prerequisites to the effectiveness of such documents. As to certain factual matters, we have relied upon a certificate of an officer of the Company and have not independently verified such matters.

Our opinion herein is expressed solely with respect to the General Corporation Law of the State of Delaware. We express no opinion to the extent that any other laws are applicable to the subject matter hereof and express no opinion and provide no assurance as to compliance with any federal or state securities law, rule or regulation.

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when sold and issued in accordance with the Registration Statement and the Prospectus, will be validly issued, fully paid and nonassessable.

We consent to the reference to our firm under the caption “Legal Matters” in the Prospectus and to the filing of this opinion as an exhibit to a Current Report on Form 8-K to be filed with the Commission for incorporation by reference into the Registration Statement. This opinion is expressed as of the date hereof, and we disclaim any responsibility to advise you of any changes in the facts stated or assumed herein or any changes in applicable law.

3175 HANOVER STREET, PALO ALTO, CA 94304-1130 T: (650) 843-5000 F: (650) 849-7400 WWW.COOLEY.COM

Syndax Pharmaceuticals, Inc.

December 9, 2020

Page Two

Cooley LLP 3175 Hanover Street Palo Alto, CA 94304-1130

t: (650) 843-5000 f: (650) 849-7400 cooley.com