Document:

EX-10.23

 Exhibit 10.23 

CONSENT AND AMENDMENT AGREEMENT 

This Consent and Amendment Agreement (this “Agreement”), dated as of December 20, 2011, by and among SYNDAX
PHARMACEUTICALS, INC., a Delaware corporation (“Borrower”), the Lenders (as defined below), and GENERAL ELECTRIC CAPITAL CORPORATION, as agent for the Lenders (in such capacity, and together with its successors and permitted
assigns, “Agent”). 
 WHEREAS, pursuant to that certain Loan and Security Agreement, dated as of
March 30, 2011, among Borrower, Agent, the financial institutions party thereto from time to time as lenders (the “Lenders”) (as it may have been and may be further amended, restated or otherwise modified from time to
time, the “Loan Agreement”), Agent and Lenders have made certain loans and other financial accommodations to Borrower subject to the terms and conditions set forth therein; and 

WHEREAS, Borrower has requested that Agent and Requisite Lenders consent to the incurrence by the Borrower of $6,250,000 of additional
unsecured, subordinated indebtedness evidenced by a series of Convertible Promissory Notes, dated on or about the date hereof, in the aggregate principal amount of up to $3,125,000 (the “Series 1 Notes”) and a second series of
Convertible Promissory Notes, to be dated on or about March 1, 2012, in the aggregate principal amount of up to $3,125,000 (the “Series 2 Notes” and together with the Series 1 Notes, collectively, the “New
Notes”), issued under a certain Note and Warrant Purchase Agreement, dated on or about the date hereof (the “New NPA”), by and among the Borrower, and the investors party thereto, which indebtedness (i) shall be
subordinated to all Obligations in all respects, (ii) shall not require payment of any kind (including principal, interest, fees or other costs related thereto) until all Obligations shall have been indefeasibly paid in full; provided,
that such financing may be converted to equity at any time and payment of cash in lieu of the issuance of fractional shares in connection with such conversion may be made, and (iii) shall otherwise be in form and substance reasonably
satisfactory to Agent; and 
 WHEREAS, Agent and Lenders constituting at least the Requisite Lenders are willing to agree to such
requests, subject to and in accordance with the terms and conditions set forth in this Agreement. 
 NOW, THEREFORE, each of
Borrower, Requisite Lenders and Agent hereby agrees as follows: 
 1. Recitals; Definitions. The foregoing recitals, including
all terms defined therein, are incorporated herein and made a part hereof. All capitalized terms used but not otherwise defined herein have the meanings given such terms in the Loan Agreement. 

2. Consent. Effective as of the date hereof, and in accordance with Section 10.08 of the Loan Agreement, Agent and Lenders
constituting at least the Requisite Lenders hereby (i) consent to the issuance of the New Notes, the execution and delivery of the New NPA and the other documents related thereto, and the incurrence of the Indebtedness thereunder, and
(ii) waive any Default or Event of Default that would otherwise arise, but for this Agreement, under Section 8.1 of the Loan Agreement by reason of the foregoing. 

3. Amendments. Subject to the terms and conditions of this Agreement: 

 

	 	A.	Section 4.1(r) of the Loan Agreement is hereby amended by replacing the clause “(the “Subordination Agreement”)” with the clause “(the “First Subordination
Agreement”)”. 

	 	B.	Section 4.1(s) of the Loan Agreement is hereby amended by replacing the clause “the Subordination Agreement” with the clause “the Subordination Agreements”. 

 

	 	C.	Section 6.9(a) of the Loan Agreement is hereby amended by replacing the term “Subordination Agreement” with the term “First Subordination Agreement”. 

 

	 	D.	Section 7.2 of the Loan Agreement is hereby amended by deleting clause (d) thereof in its entirety and replacing such clause with the following: 

“ (d) unsecured Indebtedness in an aggregate amount not to exceed $12,250,000, $6,000,000 of which is subordinated to the
Obligations pursuant to the First Subordination Agreement and up to $6,250,000 of which is subordinated to the Obligations pursuant to that certain Subordination Agreement, dated as of December 20, 2011, executed by the Borrower and each
investor party to that certain Note Purchase and Warrant, dated as December 20, 2011, by and among the Borrower and the investors party thereto (the “Second Subordination Agreement” and together with the First Subordination
Agreement, each a “Subordination Agreement” and, collectively, the “Subordination Agreements”), ” 
 4.
Conditions. The foregoing is subject to the following conditions: 
  

	 	A.	No Default or Event of Default shall have occurred and be continuing other than the Defaults or Events of Default waived pursuant to Section 2 above; and 

 

	 	B.	Borrower shall have delivered true and complete copies of the Series 1 Notes, the New NPA and such further documents, information, certificates, records and filings as Agent may reasonably request. 

5. Covenants. Borrower shall deliver true and complete copies of the Series 2 Notes and such further documents, information,
certificates, records and filings as Agent may reasonably request within 3 business days of the execution and delivery thereof. 
 6.
Reaffirmation of Debt Documents. By executing and delivering this Agreement, Borrower hereby (i) reaffirms, ratifies and confirms its Obligations under the Loan Agreement, the Notes and the other Debt Documents, (ii) agrees
that this Agreement shall be a “Debt Document” under the Loan Agreement and (iii) hereby expressly agrees that the Loan Agreement, the Notes and each other Debt Document shall remain in full force and effect following any action
contemplated in connection herewith. 
 7. Reaffirmation of Grant of Security Interest in Collateral. Borrower hereby
expressly reaffirms, ratifies and confirms its obligations under the Loan Agreement, including its mortgage, grant, pledge and hypothecation to the Agent for the benefit of the Agent and each Lender, of the lien on and security interest in, all of
its right, title and interest in, all of the Collateral. 
 8. Confirmation of Representations and Warranties; Liens; No
Default. Borrower hereby confirms that (i) all of the representations and warranties set forth in the Debt Documents continue to be true and correct as of the date hereof, except to the extent such representations and warranties by
their terms expressly relate only to a prior date (in which case such representations and warranties shall be true and correct as of such prior date); (ii) there are no Defaults or Events of Default that have not been waived or cured other than
the Defaults or Events of Default waived pursuant to Section 2 above; (iii)

  
 2 

 
Agent has and shall continue to have valid, enforceable and perfected first-priority liens, subject to Permitted Liens, on and security interests in the Collateral and all other collateral
heretofore granted by Borrower to Agent, for the benefit of the Agent and each Lender, pursuant to the Debt Documents or otherwise granted to or held by Agent, for the benefit of the Agent and each Lender, and (iv) the agreements and
obligations of Borrower contained in the Debt Documents and in this Agreement constitute the legal, valid and binding obligations of Borrower, enforceable against Borrower in accordance with their respective terms, except as the enforceability
thereof may be limited by bankruptcy, insolvency or other similar laws of general application affecting the enforcement of creditors’ rights or by the application of general principles of equity ; provided, however, with respect to this clause
(iv), to the extent that this Agreement is not enforceable against Borrower, the obligations of the Agent and Lenders contained herein with respect to such parties are null and void. 

9. No Other Consents or Amendments. The consent in this Agreement is applicable only to the matters set forth in
Section 2 above, and does not constitute a future consent nor a consent to anything other than the matters expressly set forth herein. Except as expressly set forth in this Agreement, the Loan Agreement and all other Debt Documents shall
remain unchanged and in full force and effect. This Agreement shall be limited precisely and expressly as drafted and shall not be construed as a consent to the amendment, restatement, modification, supplementation or waiver of any other terms or
provisions of the Loan Agreement or any other Debt Document. 
 10. Intentionally Omitted.  

11. Costs and Expenses. Borrower shall be responsible for (i) a consent fee of $1,500.00 and (ii) the reimbursement of
all fees and expenses of Agent’s in-house and outside counsel and other out of pocket costs and expenses incurred by Agent and Lenders in connection with the preparation and negotiation of this Agreement. Such fees, costs and expenses, as
limited by the preceding sentence, shall be due and payable upon demand of Agent, and if not paid promptly upon such demand, all such fees, costs and expenses shall become part of the Obligations. 

12. Governing Law. This Agreement shall be governed by and construed in accordance with the laws of the State of New York. 

13. Successors/Assigns. This Agreement shall bind, and the rights hereunder shall inure to, the respective successors and
assigns of the parties hereto, subject to the provisions of the Debt Documents. 
 14. Headings. Section headings in this
Agreement are included for convenience of reference only and shall not constitute a part of this Agreement for any other purpose. 
 15.
Counterparts. This Agreement may be executed in counterparts, and such counterparts taken together shall be deemed to constitute one and the same instrument. Delivery of an executed counterpart of this Agreement by facsimile or other
electronic method of transmission shall be equally as effective as delivery of an original executed counterpart of this Agreement. Any party delivering an executed counterpart of this Agreement by facsimile or other electronic method of transmission
also shall deliver an original executed counterpart of this Agreement but the failure to deliver an original executed counterpart shall not affect the validity, enforceability or binding effect of this Agreement. 

[SIGNATURE PAGE TO FOLLOW] 

  
 3 

 IN WITNESS WHEREOF, the undersigned have caused this Consent to be duly executed by their
duly authorized representatives, all as of the day and year first above written. 
  

			
	BORROWER:
	
	Syndax Pharmaceuticals, Inc., a Delaware corporation
		
	By:	 	/s/ Joanna Horobin, M.D.
	Name:	 	Joanna Horobin, M.D.
	Title:	 	Chief Executive Officer

 [Signatures Continue on Following Page] 

  
 S-1 

 
			
	AGENT AND LENDER:
	
	General Electric Capital Corporation, a Delaware corporation
		
	By:	 	/s/ Jacqueline K. Blechinger
	Name:	 	Jacqueline K. Blechinger
	Its:	 	Duly Authorized Signatory

 [End of Signature Pages] 

  
 S-2EX-10.24

 Exhibit 10.24 

EXECUTION VERSION 

CONSENT AND AMENDMENT AGREEMENT 

This Consent and Amendment Agreement (this “Agreement”), dated as of June 28, 2012, by and among SYNDAX
PHARMACEUTICALS, INC., a Delaware corporation (“Borrower”), the Lenders (as defined below), and GENERAL ELECTRIC CAPITAL CORPORATION, as agent for the Lenders (in such capacity, and together with its successors and permitted
assigns, “Agent”). 
 WHEREAS, pursuant to that certain Loan and Security Agreement, dated as of
March 30, 2011, among Borrower, Agent, the financial institutions party thereto from time to time as lenders (the “Lenders”), as amended by that certain Consent and Amendment Agreement, dated as of December 20, 2011
(as so amended and as it may have been and may be further amended, restated or otherwise modified from time to time, the “Loan Agreement”), Agent and Lenders have made certain loans and other financial accommodations to
Borrower subject to the terms and conditions set forth therein; 
 WHEREAS, on the Closing Date, Borrower caused its investors to
deliver that certain Subordination Agreement, dated as of March 30, 2011 (the “First Subordination Agreement”), among Agent and certain investors party to that certain Note and Warrant Purchase Agreement, dated as of
August 3, 2010 (the “2010 NPA”), pursuant to which such investors, among other things, subordinated approximately $6,000,000 of outstanding Indebtedness of Borrower to the Obligations, which Indebtedness is evidenced by
a series of Convertible Promissory Notes issued under the 2010 NPA (the “2010 Notes”); 
 WHEREAS, Borrower
requested and, pursuant to that certain Consent and Amendment Agreement, dated as of December 20, 2011, between Agent and Borrower (the “2011 Consent”), Agent and Requisite Lenders consented to the incurrence by Borrower
of up to $6,250,000 of additional unsecured, subordinated Indebtedness evidenced by a series of Convertible Promissory Notes, dated December 20, 2011, December 28, 2011 and April 2, 2012, (collectively, the “2011
Notes”), issued under that certain Note and Warrant Purchase Agreement, dated December 20, 2011 (the “2011 NPA”), by and among Borrower and the investors party thereto, which Indebtedness was subordinated to
the Obligations pursuant to that certain Amended and Restated Subordination Agreement, dated as of December 20, 2011, which amends, restates and continues the First Subordination Agreement; 

WHEREAS, in connection with the issuance of the 2011 Notes, Borrower (i) amended and restated its certificate of incorporation by
filing the amended and restated certificate of incorporation attached hereto as Exhibit A (the “2011 Charter Amendment”), (ii) entered into the 2011 NPA and issued the 2011 Notes thereunder and (iii) amended
the 2010 Notes (the “2011 Notes Amendment” and together with the 2011 Charter Amendment and the execution and delivery of the 2011 NPA and issuance of the 2011 Notes, collectively, the “2011
Amendments”) each of which, but for the 2011 Consent and this Agreement, would have been be prohibited pursuant to Sections 7.2 and 7.11 of the Loan Agreement; 

WHEREAS, Borrower has requested that Agent and Requisite Lenders consent to the incurrence by the Borrower of up to $3,000,000 of
additional unsecured, subordinated Indebtedness evidenced by a series of Convertible Promissory Notes, dated on or about the date hereof, in the aggregate principal amount of up to $3,000,000 (the “2012 Notes”), issued under
the 2011 NPA, as amended by that certain Amendment to Note and Warrant Purchase Agreement, dated on or about the date hereof (the “NPA Amendment”), which Indebtedness (i) shall be subordinated to all Obligations in all
respects pursuant to a Subordination Agreement, dated as of the date hereof (the “2012 Subordination Agreement”), 

 
executed by the Borrower and each investor that is purchasing a 2012 Note, which investors represent, in the aggregate, approximately 99% of the investors party to the 2010 NPA and the 2011 NPA,
(ii) shall not require payment of any kind (including principal, interest, fees or other costs related thereto) until all Obligations shall have been indefeasibly paid in full; provided, that such financing may be converted to equity at
any time and payment of cash in lieu of the issuance of fractional shares in connection with such conversion may be made, and (iii) shall otherwise be in form and substance reasonably satisfactory to Agent; 

WHEREAS, in connection with the issuance of the 2012 Notes, Borrower is required to (i) amend its certificate of incorporation
pursuant to a certificate of amendment in the form attached hereto as Exhibit B (the “2012 Charter Amendment”), (ii) enter into the NPA Amendment and issue the 2012 Notes thereunder and (iii) amend the 2010
Notes and the 2011 Notes (the “2012 Notes Amendments”, and together with the 2012 Charter Amendment, the NPA Amendment and the issuance of the 2012 Notes, collectively, the “2012 Amendments”), each of
which, but for this Agreement, would otherwise be prohibited pursuant to Sections 7.2 and 7.11 of the Loan Agreement; 
 WHEREAS,
Borrower has requested that Agent and Requisite Lenders acknowledge, ratify and reaffirm their consent to the 2011 Amendments and further consent to the 2012 Amendments; and 

WHEREAS, Agent and Lenders constituting at least the Requisite Lenders are willing to agree to such requests, subject to and in
accordance with the terms and conditions set forth in this Agreement. 
 NOW, THEREFORE, each of Borrower, Requisite Lenders and
Agent hereby agrees as follows: 
 1. Recitals; Definitions. The foregoing recitals, including all terms defined therein, are
incorporated herein and made a part hereof. All capitalized terms used but not otherwise defined herein have the meanings given such terms in the Loan Agreement. 

2. Consent. Effective as of December 20, 2011, and in accordance with Section 10.08 of the Loan Agreement, Agent and
Lenders constituting at least the Requisite Lenders hereby (i) acknowledge, ratify and reaffirm their consent to the issuance of the 2011 Notes, the execution and delivery of the 2011 NPA and the other documents related thereto, and the
incurrence of the Indebtedness thereunder, (ii) consent to the other 2011 Amendments, and (iii) waive any Default or Event of Default that would otherwise arise, but for the 2011 Consent and this Agreement, under Section 8.1 of the
Loan Agreement by reason of the foregoing. Effective as of the date hereof, and in accordance with Section 10.08 of the Loan Agreement, Agent and Lenders constituting at least the Requisite Lenders hereby (i) consent to the issuance of the
2012 Notes, the execution and delivery of the NPA Amendment and the other documents related thereto, and the incurrence of the Indebtedness under the 2011 NPA as amended by the NPA Amendment, (ii) consent to the other 2012 Amendments,
(iii) consent to the delivery of the complete annual audited financial statements, as described in Section 6.3(c) of the Loan Agreement, for the 2011 fiscal year within two hundred and seventy (270) days from the end of the 2011
fiscal year end, or, if sooner, at such time as Borrower’s Board of Directors receives the certified audit, and (iv) waive any Default or Event of Default that would otherwise arise, but for this Agreement, under Section 8.1 of the
Loan Agreement by reason of the foregoing. 
 3. Amendments. Subject to the terms and conditions of this Agreement,
Section 7.2 of the Loan Agreement is hereby amended by deleting clause (d) thereof in its entirety and replacing such clause with the following: 

  
 2 

 “ (d) subordinated, unsecured Indebtedness in an aggregate amount not to exceed
$15,250,000 (the “Subordinated Indebtedness”), which subordinated, unsecured Indebtedness is evidenced by those certain Convertible Promissory Notes issued pursuant to that certain Note and Warrant Purchase Agreement, dated as of
August 3, 2010, by and among the Borrower and each investor party thereto (the “2010 NPA”), that certain Note and Warrant Purchase Agreement, dated as of December 20, 2011, by and among the Borrower and each investor party
thereto (the “2011 NPA”), as amended by that certain Amendment to Note Warrant and Purchase Agreement, dated as of June     , 2012, by and among the Borrower and each investor party thereto (the 2011 NPA,
as so amended, the “2012 NPA”), which Indebtedness is subordinated to the Obligations pursuant to (i) the First Subordination Agreement (which subordinates $6,000,000), (ii) that certain Amended and Restated Subordination
Agreement, dated as of December 20, 2011, by and among each of the parties to the First Subordination Agreement and certain other investors who are parties to the 2011 NPA (which amends, restates and continues the First Subordination Agreement
subordinating an additional $6,250,000 for a total of $12,250,000, the “2011 Subordination Agreement”), and (iii) that certain Subordination Agreement, dated as of June 28, 2012, by and among the parties to the First
Subordination Agreement and the 2011 Subordination Agreement other than two individual investors who have opted not to participate in the offering under the 2012 NPA (which Subordination Agreement separately subordinates $3,000,000, the
“2012 Subordination Agreement” and together with the 2011 Subordination Agreement (which, for the avoidance of doubt, includes the First Subordination Agreement), collectively, the “Subordination Agreements”)”.

 4. Conditions. The foregoing is subject to the following conditions: 

 

	 	A.	Agent shall have received a counterpart of this Agreement duly executed by each Loan Party; 

  

	 	B.	Agent shall have received a counterpart of the 2012 Subordination Agreement duly executed by each investor that is purchasing a 2012 Note pursuant to the 2011 NPA, as amended by the NPA Amendment, and consented to by
the Borrower; 

  

	 	C.	Borrower shall have delivered a certificate of an authorized officer of the Borrower, providing verification of an incumbency and attaching (i) Borrower’s board resolutions approving the transactions
contemplated by this Agreement, (ii) Borrower’s governing documents, and (iii) an updated perfection certificate; 

  

	 	D.	Borrower shall have delivered true and complete copies of the 2012 Notes, the NPA Amendment, the 2012 Charter Amendment and the other amendments referenced herein and such further documents, information, certificates,
records and filings as Agent may reasonably request; and 

  

	 	E.	(i) No Default or Event of Default shall have occurred and be continuing other than the Defaults or Events of Default waived pursuant to Section 2 above, (ii) all representations and warranties in
Section 5 of the Loan Agreement shall be true and correct as of the date hereof, (iii) each condition set forth in this Section 4 of this Agreement shall have been satisfied, and (iv) Agent shall have received a certificate from
an authorized officer of the Borrower confirming each of the foregoing. 

  
 3 

 5. Reaffirmation of Debt Documents. By executing and delivering this Agreement,
Borrower hereby (i) reaffirms, ratifies and confirms its Obligations under the Loan Agreement, the Notes and the other Debt Documents, (ii) agrees that this Agreement shall be a “Debt Document” under the Loan Agreement and
(iii) hereby expressly agrees that the Loan Agreement, the Notes and each other Debt Document shall remain in full force and effect following any action contemplated in connection herewith. 

6. Reaffirmation of Grant of Security Interest in Collateral. Borrower hereby expressly reaffirms, ratifies and confirms its
obligations under the Loan Agreement, including its mortgage, grant, pledge and hypothecation to the Agent for the benefit of the Agent and each Lender, of the lien on and security interest in, all of its right, title and interest in, all of the
Collateral. 
 7. Confirmation of Representations and Warranties; Liens; No Default. Borrower hereby confirms that (i) all
of the representations and warranties set forth in the Debt Documents continue to be true and correct as of the date hereof, except to the extent such representations and warranties by their terms expressly relate only to a prior date (in which case
such representations and warranties shall be true and correct as of such prior date); (ii) there are no Defaults or Events of Default that have not been waived or cured other than the Defaults or Events of Default waived pursuant to
Section 2 above; (iii) Agent has and shall continue to have valid, enforceable and perfected first-priority liens, subject to Permitted Liens, on and security interests in the Collateral and all other collateral heretofore granted
by Borrower to Agent, for the benefit of the Agent and each Lender, pursuant to the Debt Documents or otherwise granted to or held by Agent, for the benefit of the Agent and each Lender, and (iv) the agreements and obligations of Borrower
contained in the Debt Documents and in this Agreement constitute the legal, valid and binding obligations of Borrower, enforceable against Borrower in accordance with their respective terms, except as the enforceability thereof may be limited by
bankruptcy, insolvency or other similar laws of general application affecting the enforcement of creditors’ rights or by the application of general principles of equity ; provided, however, with respect to this clause (iv), to the extent that
this Agreement is not enforceable against Borrower, the obligations of the Agent and Lenders contained herein with respect to such parties are null and void. 

8. No Other Consents or Amendments. The consent in this Agreement is applicable only to the matters set forth in
Section 2 above, and does not constitute a future consent nor a consent to anything other than the matters expressly set forth herein. Except as expressly set forth in this Agreement, the Loan Agreement and all other Debt Documents shall
remain unchanged and in full force and effect. This Agreement shall be limited precisely and expressly as drafted and shall not be construed as consent to the amendment, restatement, modification, supplementation or waiver of any other terms or
provisions of the Loan Agreement or any other Debt Document. 
 9. Intentionally Omitted.  

10. Costs and Expenses. Borrower shall be responsible for (i) a consent fee of $1,500.00 and (ii) the reimbursement of
all fees and expenses of Agent’s in-house and outside counsel and other out of pocket costs and expenses incurred by Agent and Lenders in connection with the preparation and negotiation of this Agreement. Such fees, costs and expenses, as
limited by the preceding sentence, shall be due and payable upon demand of Agent, and if not paid promptly upon such demand, all such fees, costs and expenses shall become part of the Obligations. 

11. Governing Law. This Agreement shall be governed by and construed in accordance with the laws of the State of New York. 

  
 4 

 12. Successors/Assigns. This Agreement shall bind, and the rights hereunder shall
inure to, the respective successors and assigns of the parties hereto, subject to the provisions of the Debt Documents. 
 13.
Headings. Section headings in this Agreement are included for convenience of reference only and shall not constitute a part of this Agreement for any other purpose. 

14. Counterparts. This Agreement may be executed in counterparts, and such counterparts taken together shall be deemed to
constitute one and the same instrument. Delivery of an executed counterpart of this Agreement by facsimile or other electronic method of transmission shall be equally as effective as delivery of an original executed counterpart of this Agreement.
Any party delivering an executed counterpart of this Agreement by facsimile or other electronic method of transmission also shall deliver an original executed counterpart of this Agreement but the failure to deliver an original executed counterpart
shall not affect the validity, enforceability or binding effect of this Agreement. 
 [SIGNATURE PAGE TO FOLLOW] 

  
 5 

 IN WITNESS WHEREOF, the undersigned have caused this Consent to be duly executed by their
duly authorized representatives, all as of the day and year first above written. 
  

			
	 BORROWER:

	
	Syndax Pharmaceuticals, Inc., a Delaware corporation
		
	 By:
	 	/s/ Arlene M. Morris
	 Name:
	 	Arlene M. Morris
	 Title:
	 	Chief Executive Officer

 [Signatures Continue on Following Page] 

  
 S-1 

 
			
	 AGENT AND LENDER:

	
	General Electric Capital Corporation, a Delaware corporation
		
	 By:
	 	/s/ Jacqueline K. Blechinger
	 Name:
	 	Jacqueline K. Blechinger
	 Its:
	 	Duly Authorized Signatory

 [End of Signature Pages] 

  
 S-2 

 Exhibit A 

2011 Charter Amendment 

 FOURTH AMENDED AND RESTATED CERTIFICATE OF INCORPORATION 

OF 
 SYNDAX
PHARMACEUTICALS, INC. 
 Syndax Pharmaceuticals, Inc., a corporation organized and existing under the laws of the State of Delaware,
hereby certifies as follows: 
 The name of this corporation is Syndax Pharmaceuticals, Inc. This corporation was originally incorporated
under the same name, and the original Certificate of Incorporation of this corporation was filed with the Secretary of State of the State of Delaware on October 11, 2005. An Amended and Restated Certificate of Incorporation of this Corporation
was filed with the Secretary of State of the State of Delaware on March 29, 2007, January 22, 2010 and on August 2, 2010 all under its present name. 

The text of the Third Amended and Restated Certificate of Incorporation is hereby amended and restated in its entirety to read as follows:

 ARTICLE I 
 The name
of this corporation is Syndax Pharmaceuticals, Inc. 
 ARTICLE II 

The address of this corporation’s registered office in the State of Delaware is 2711 Centerville Road, Suite 400, City of Wilmington,
19808, County of New Castle, Delaware. The name of its registered agent at such address is Corporation Service Company. 
 ARTICLE III

 The purpose of this corporation is to engage in any lawful act or activity for which a corporation may be organized under the General
Corporation Law of the State of Delaware. 
 ARTICLE IV 

This corporation is authorized to issue two classes of stock to be designated, respectively, “Common Stock” and
“Preferred Stock.” The total number of shares which this corporation is authorized to issue is Two Hundred Fifty-Four Million (254,000,000) shares. One Hundred Six Million (106,000,000) shares shall be Common Stock with a
par value of $0.0001 per share and One Hundred Forty-Eight Million (148,000,000) shares shall be Preferred Stock with a par value of $0.001 per share, Seventy-Four Million (74,000,000) shares of which shall be designated Series A Preferred
Stock (“Series A Preferred Stock”) and Seventy-Four Million (74,000,000) shares of which shall be designated Series A-1 Preferred Stock (“Series A-1 Preferred Stock” and together with the Series A Preferred
Stock, the “Preferred Stock”), This corporation shall from time to time in accordance with the laws of the State of Delaware increase the authorized amount of its Common Stock if at any time the number of shares of Common Stock
remaining unissued and available for issuance upon conversion of the Preferred Stock shall not be sufficient to permit conversion of the Preferred Stock. Subject to the provisions herein, the number of authorized shares of Common Stock may be
increased or decreased (but not below the number of shares thereof then outstanding) by the affirmative vote of the holders of shares of stock of this corporation representing a majority of the votes represented by all outstanding shares of stock of
this corporation entitled to vote, irrespective of the provisions of Section 242(b)(2) of the Delaware General Corporation Law. 

 ARTICLE V 

The relative rights, preferences, privileges and restrictions granted to or imposed upon the respective classes and series of the shares of
capital stock or the holders thereof are as follows: 
 1. Dividend Provisions. Prior and in preference to any declaration or payment
of any dividends to the holders of shares of Common Stock, the holders of shares of the Series A Preferred Stock and Series A-1 Preferred Stock shall be entitled to receive dividends, on a pari passu basis, out of any assets legally available
therefor (payable other than in Common Stock or other securities and rights convertible into or entitling the holder thereof to receive, directly or indirectly, additional shares of Common Stock of this corporation), at the rate of eight percent
(8%) of the applicable Original Issue Price (as defined herein) per share per annum. Such dividends shall be payable when, as and if declared by the board of directors of this corporation, and shall not be cumulative. In the event that the
board of directors of this corporation declares a dividend, the amount of which is insufficient to permit payment of the full aforesaid dividends, such dividends will be paid ratably to each holder in proportion to the dividend amounts to which each
holder of Preferred Stock is entitled. After payment of the full amount of the aforesaid dividends, any additional dividends declared shall be distributed to the holders of Common Stock. In addition, holders of shares of Series A Preferred Stock and
Series A-1 Preferred Stock shall be entitled to receive, on an as-converted basis, dividends declared and paid to holders of Common Stock. The “Original Issue Price” of the Series A Preferred Stock and Series A-1 Preferred Stock
shall be Ninety-One Cents ($0.91) per share (as adjusted for stock splits, stock dividends, recapitalization and similar events). 
 2.
Liquidation Preference. 
 (a) Preferred Preference. 

(i) In the event of any Liquidating Transaction (as defined below), either voluntarily or involuntarily, the holders of the Preferred Stock
shall be entitled to receive, prior and in preference to any distribution of any of the assets or surplus funds of this corporation (or distribution of consideration in connection with a Liquidating Transaction (defined below)) to the holders of
Common Stock, on a pari passu basis, an amount equal to the applicable Original Issue Price per share for each share of Preferred Stock then so held, plus a further amount equal to any dividends declared but unpaid on such shares. All of the
preferential amounts to be paid to the holders of the Preferred Stock under this Section 2(a)(i) shall be paid or set apart for payment before the payment or setting apart for payment of any amount for, or the distribution of any assets
of this corporation to, the holders of the Common Stock in connection with such Liquidating Transaction. 
 (ii) If, upon such Liquidating
Transaction the assets of this corporation are insufficient to provide for the cash payment of the full aforesaid preferential amounts to the holders of the Preferred Stock, such assets as are available shall be distributed ratably among the holders
of the Preferred Stock in proportion to the full preferential amount each such holder is otherwise entitled to receive. 

 (iii) After payment has been made to the holders of the Preferred Stock of the full amounts to
which they are entitled as provided in Section 2(a)(i) above, the remaining assets of this corporation available for distribution to stockholders shall be distributed pro rata among the holders of Common Stock and Preferred Stock (on an
as-converted to Common Stock basis) until the holders of Preferred Stock have received an amount per share, including the amounts to which they are entitled as provided in Section 2(a)(i) above, equal to three (3) multiplied by the
Original Issue Price per share of such Preferred Stock, for all of such holders’ shares of Preferred Stock (the “Maximum Participation Amount”); provided, however, that the holders of the Preferred Stock shall be entitled to
receive the greater of (x) the Maximum Participation Amount and (y) the amount such holder would have received if all shares of its Preferred Stock had been converted into Common Stock immediately prior to such distribution. 

(iv) After payment has been made to the holders of the Preferred Stock in the full amounts to which they are entitled as provided in
Sections 2(a)(i) and 2(a)(iii), any remaining assets or property of this corporation shall be distributed on a pro rata basis among the holders of the Common Stock. 

(v) If any portion of the consideration payable to the stockholders of this corporation is placed into escrow and/or is payable to the
stockholders of this corporation subject to contingencies, the agreement governing such transaction shall provide that (x) the portion of such consideration that is not placed in escrow and not subject to any contingencies (the “Initial
Consideration”) shall be allocated among the holders of capital stock of this corporation in accordance with the liquidation preference order as set forth in this Section 2 as if the Initial Consideration were the only consideration
payable in connection with such Liquidating Transaction and (y) any additional consideration which becomes payable to the stockholders of this corporation upon release from escrow or satisfaction of contingencies shall be allocated among the
holders of capital stock of this corporation in accordance with the liquidation preference order as set forth in this Section 2 after taking into account the previous payment of the Initial Consideration as part of the same transaction. 

For purposes of this Section 2, a “Liquidating Transaction” of this corporation shall mean a
(i) liquidation, dissolution or winding up of this corporation, (ii) sale, conveyance, license or other disposition of all or substantially all of the assets, property or business of this corporation, or (iii) merger or consolidation
with or into any other corporation. 
 (b) Notice of Liquidating Transaction. This corporation shall give each holder of record of
Preferred Stock written notice of any impending Liquidating Transaction not later than ten (10) days prior to the stockholders’ meeting called to approve such Liquidating Transaction, or ten (10) days prior to the closing of such
Liquidating Transaction, whichever is earlier, and shall also notify such holders in writing of the final approval of such Liquidating Transaction. The first of such notices shall describe the material terms and conditions of the impending
Liquidating Transaction and the provisions of this Section 2, and this corporation shall thereafter give such holders prompt notice of any material changes. Unless such notice requirements are waived, the Liquidating Transaction shall
not take place sooner than ten (10) days after this corporation has given the first notice provided for herein or sooner than ten (10) days after this corporation has given notice of any material changes provided for herein.
Notwithstanding the other provisions of this Certificate of Incorporation, all notice periods or 

 
requirements in this Certificate of Incorporation applicable to the holders of Preferred Stock may be shortened or waived, either before or after the action for which notice is required, upon the
written consent of the holders of at least sixty percent (60%) of the voting power of the outstanding shares of Preferred Stock that are entitled to such notice rights. 

(c) Consent for Certain Repurchases. Each holder of an outstanding share of Preferred Stock shall be deemed to have consented, for
purposes of Section 160 of the General Corporation Law of the State of Delaware (and, if applicable, Sections 502, 503 and 506 of the California Corporations Code), to distributions made by this corporation in connection with the repurchase of
shares of Common Stock issued to or held by employees or consultants upon termination of their employment or services pursuant to agreements providing for the right of said repurchase between this corporation and such persons but only to the extent
each distribution equals the original purchase price of such shares being repurchased. 
 3. Voting Rights. 

(a) The Series A Preferred Stock, voting as a separate class, shall be entitled to elect three (3) members of the board of directors (the
“Series A Directors”), the Common Stock, voting as a separate class, shall be entitled to elect two (2) members of the board of directors (the “Common Directors”), the holders of a majority of the Common Stock
and a majority of the Preferred Stock, each voting as a separate class on an as converted basis, shall be entitled to elect one (1) member, and the holders of at least sixty percent (60%) of the Preferred Stock and a majority of the Common
Stock, each voting as a separate class, shall be entitled to elect any remaining directors. 
 (b) On all other matters, except as
specifically provided herein or as otherwise required by law, holders of the Preferred Stock shall have full voting rights and powers equal to the voting rights and powers of the holders of Common Stock, and shall be entitled to vote, together with
the holders of Common Stock, with respect to any matters upon which holders of Common Stock have the right to vote. Except as otherwise provided herein, the holder of each share of Common Stock issued and outstanding shall have one vote and the
holder of each share of Preferred Stock shall be entitled to the number of votes equal to the largest number of shares of Common Stock into which such share of Preferred Stock could be converted at the record date for determination of the
stockholders entitled to vote on such matters, or, if no such record date is established, at the date such vote is taken or any written consent of stockholders is solicited, such votes to be counted together with all other shares of stock of this
corporation having general voting power and not separately as a class. For purposes of this Section 3, the “voting power of the shares of Preferred Stock” shall mean the number of votes equal to the number of shares of Common
Stock into which such shares of Preferred Stock could be converted at the dates provided in the preceding sentence. Fractional votes by the holders of Preferred Stock shall not, however, be permitted and any fractional voting rights shall (after
aggregating all shares into which shares of Preferred Stock held by each holder could be converted) be rounded to the nearest whole number. 

4. Conversion. The holders of the Preferred Stock shall have conversion rights as follows (the “Conversion Rights”):

 (a) Right to Convert. Each share of Series A Preferred Stock and Series A-1 Preferred Stock shall be convertible into shares
of Common Stock without the payment of any 

 
additional consideration by the holder thereof and, at the option of the holder thereof, at any time after the date of issuance of such share, at the office of this corporation or any transfer
agent for the Preferred Stock and shall be convertible into the number of fully paid and nonassessable shares of Common Stock which results from dividing the Conversion Price (as hereinafter defined) per share in effect for each series of Preferred
Stock at the time of conversion into the per share Conversion Value (as hereinafter defined) of such series. The initial per share Conversion Price of the Series A Preferred Stock shall be Ninety-One Cents ($0.91). The per share Conversion Value of
the Series A Preferred Stock shall be Ninety-One Cents ($0.91) (as adjusted for stock splits, stock dividends, recapitalization and similar events relating to the Series A Preferred Stock). The initial per share Conversion Price of the Series A-1
Preferred Stock shall be determined in accordance with Section 4(g) hereof. The per share Conversion Value of the Series A-1 Preferred Stock shall be Ninety One Cents ($0.91) (as adjusted for stock splits, stock dividends,
recapitalization and similar events relating to the Series A Preferred Stock and Series A-I Preferred Stock). The initial Conversion Price of the Series A Preferred Stock and the Series A-1 Preferred Stock shall be subject to adjustment from time to
time as provided below, subject to the terms of Section 4(g) hereof. The number of shares of Common Stock into which a share of Preferred Stock is convertible is hereinafter referred to as the “Conversion Rate” of such
series. 
 (b) Automatic Conversion. Each share of Preferred Stock shall automatically be converted into share(s) of Common
Stock at its then effective Conversion Rate of such series of Preferred Stock immediately upon the earlier of (i) the closing of the sale of this corporation’s Common Stock in a firm commitment, underwritten public offering registered
under the Securities Act of 1933, as amended (“Securities Act”), with aggregate offering proceeds to this corporation (before deduction for underwriters’ discounts and expenses relating to the issuance) of at least Fifty
Million Dollars ($50,000,000) and a public offering price per share equal to at least three (3) times the Original Issue Price for the Series A Preferred Stock, or (ii) at the election of the holders of at least sixty percent (60%) of
the outstanding shares of the Preferred Stock voting together as a single class on an as-converted basis. 
 (c) Mechanics of
Conversion. Before any holder of Preferred Stock shall be entitled to convert the same into shares of Common Stock, the holder shall surrender the certificate(s) therefor, duly endorsed, at the office of this corporation or of any transfer agent
for the Preferred Stock and shall give written notice to this corporation at such office that the holder elects to convert the same (except that no such written notice of election to convert shall be necessary in the event of an automatic conversion
pursuant to Section 4(b) hereof). This corporation shall, as soon as practicable thereafter, issue and deliver at such office to such holder of Preferred Stock certificate(s) for the number of shares of Common Stock to which such holder
shall be entitled as aforesaid. Such conversion shall be deemed to have been made immediately prior to the close of business on the date of such surrender of the shares of Preferred Stock to be converted (except that in the case of an automatic
conversion pursuant to Section 4(b)(i) hereof such conversion shall be deemed to have been made immediately prior to the closing of the offering referred to in Section 4(b)(i)) or in the case of an automatic conversion
pursuant to Section 4(b)(ii) hereof, immediately prior to the close of business on the date of the election referred to in Section 4(b)(ii) and the person or persons entitled to receive the shares of Common Stock issuable
upon such conversion shall be treated for all purposes as the record holder or holders of such shares of Common Stock on such date. If the conversion is in 

 
connection with an underwritten public offering of securities registered pursuant to the Securities Act the conversion may, at the option of any holder tendering such Preferred Stock for
conversion, be conditioned upon the closing with the underwriters of the sale of securities pursuant to such offering, in which event any persons entitled to receive Common Stock upon conversion of such Preferred Stock shall not be deemed to have
converted such Preferred Stock until immediately prior to the closing of such sale of securities. 
 (d) Fractional Shares. In
lieu of any fractional shares to which the holder of Preferred Stock would otherwise be entitled, this corporation shall pay cash equal to such fraction multiplied by the fair market value of one share of such series of Preferred Stock as determined
by the board of directors of this corporation. Whether or not fractional shares are issuable upon such conversion shall be determined on the basis of the total number of shares of Preferred Stock of each holder at the time converting into Common
Stock and the number of shares of Common Stock issuable upon such aggregate conversion. 
 (e) Adjustment of Conversion Price.
The Conversion Price of the Series A Preferred Stock (“Series A Conversion Price”) shall be subject to independent adjustment from time to time as follows: 

(i) Definitions. For purposes of this paragraph 4(e), the following definitions shall apply: 

(A) “Excluded Stock” shall mean: 

(1) all shares of Common Stock issued or deemed issued to officers, directors, consultants or employees of this corporation, pursuant to a
stock option plan or other agreement approved by a majority of the board of directors of this corporation; 
 (2) all shares of Common Stock
issued or deemed issued in connection with research and development partnerships, licensing, corporate partnering, collaborative arrangements or similar transactions approved by the holders of at least sixty percent (60%) of the outstanding
Preferred Stock; 
 (3) all securities issued pursuant to dividends or distributions on the Preferred Stock; 

(4) securities to financial institutions or lessors issued in connection with commercial credit arrangements, equipment financings, commercial
property lease transactions, or similar transactions approved by a majority of the board of directors of this corporation; 
 (5) capital
stock issued in connection with bona fide acquisitions, mergers, consolidations or similar business combinations, provided that such issuance has been approved by the holders of at least sixty percent (60%) of the outstanding Preferred Stock;

 (6) Common Stock issuable upon conversion of the Preferred Stock; 

(7) Series A-1 Preferred Stock issued upon conversion of the Series A Preferred Stock; 

 (8) (i) warrants to purchase Series A Preferred Stock (the “Series A Warrants”)
issued in connection with the Purchase Agreement (as defined below) and (ii) warrants to purchase Common Stock issued pursuant to (a) that certain Note and Warrant Purchase Agreement dated August 3, 2010, by and among this corporation
and certain other parties as amended from time to time, and (b) that certain Note and Warrant Purchase Agreement to be entered into on or about the filing date hereof, by and among this corporation and certain other parties, as amended from
time to time (the “2011 Note and Warrant Purchase Agreement”) (collectively, the “Common Stock Warrants”); 

(9) (i) Series A Preferred Stock issued upon exercise of the Series A Warrants, (ii) Common Stock issued upon exercise of the Common
Stock Warrants; and (iii) any shares of this corporation’s capital stock issuable upon conversion of such shares of capital stock. 

(B) “Options” means options to purchase or rights to subscribe for Common Stock (other than Excluded Stock). 

(C) “Convertible Securities” means securities by their terms directly or indirectly convertible into or exchangeable
for Common Stock (other than Excluded Stock) and options to purchase or rights to subscribe for such convertible or exchangeable securities. 

(D) “Purchase Rights” means Options and Convertible Securities. 

(E) “Dilutive Issuance” means an issuance of Purchase Rights, or Common Stock which is not Excluded Stock, without
consideration or for a consideration per share less than the applicable Conversion Price. “Dilutive Issuance” excludes any stock dividend, subdivision or split-up, stock combination, dividend or Transaction described in Sections
4(e)(iv) through (vii) below. 
 (ii) Adjustment of Conversion Price for Dilutive Issuances of Series A Preferred Stock. If this
corporation issues or is deemed to issue any Common Stock in a Dilutive Issuance, the Series A Conversion Price in effect after each such issuance shall be adjusted to a price determined by multiplying the Series A Conversion Price in effect
immediately prior to the Dilutive Issuance by a fraction: 
 (A) the numerator of which shall be (1) the number of shares of Common
Stock outstanding and issuable on exercise of all outstanding Options and Convertible Securities immediately prior to the Dilutive Issuance, plus (2) the number of shares of Common Stock that the aggregate consideration, if any, received by
this corporation in connection with the Dilutive Issuance would purchase at such Conversion Price, and 
 (B) the denominator of which shall
be (1) the number of shares of Common Stock outstanding and issuable on exercise of all outstanding Options and Convertible Securities immediately prior to the Dilutive Issuance, plus (2) the number of shares of Common Stock issued or
deemed issued in the Dilutive Issuance. 
 (iii) For purposes of any adjustment of the Series A Conversion Price pursuant to clause
(ii) above, the following provisions shall be applicable: 
 (A) In the case of the issuance of Common Stock for cash, the
consideration shall be deemed to be the amount of cash paid therefor after deducting any 

 
discounts or commissions paid or incurred by this corporation in connection with the issuance and sale thereof. 

(B) In the case of the issuance of Common Stock for a consideration in whole or in part other than cash, the consideration other than cash
shall be deemed to be the fair market value thereof as determined by the board of directors of this corporation, in accordance with generally accepted accounting treatment; provided, however, that if at the time of such determination, this
corporation’s Common Stock is traded in the over-the-counter market or on a national or regional securities exchange, such fair market value as determined by the board of directors of this corporation shall not exceed the aggregate
“Current Market Price” (as defined below) of the shares of Common Stock being issued. 
 (C) In the case of the issuance of
Purchase Rights in a Dilutive Issuance: 
 (1) the aggregate maximum number of shares of Common Stock deliverable upon exercise of Options
shall be deemed to have been issued at the time such Options were issued and for a consideration equal to the consideration (determined in the manner provided in (iii) (A) and (B) above), if any, received by this corporation upon the
issuance of such Options plus the minimum purchase price provided in such Options covered thereby; 
 (2) the aggregate maximum number of
shares of Common Stock deliverable upon conversion or exercise of or exchange for any Convertible Securities shall be deemed to have been issued at the time such Convertible Securities were issued and for a consideration equal to the consideration
received by this corporation for any such Convertible Securities (excluding any cash received on account of accrued interest or accrued dividends), plus the minimum additional consideration, if any, to be received by this corporation upon the
conversion or exchange of such Convertible Securities (determined in the manner provided in (iii) (A) and (B) above); 
 (3)
on any change in the number of shares of Common Stock deliverable upon exercise of any such Purchase Rights or on any change in the minimum purchase price of such Purchase Rights, the Series A Conversion Price shall forthwith be readjusted to such
Series A Conversion Price as would have been obtained had the adjustment made upon (x) the issuance of such Purchase Rights not exercised, converted or exchanged prior to such change, as the case may be, been made upon the basis of such change
or (y) the issuance of options or rights related to such securities not converted or exchanged prior to such change, as the case may be, been made upon the basis of such change; and 

(4) on the expiration of any Purchase Rights, the Series A Conversion Price shall forthwith be readjusted to such Series A Conversion Price as
would have obtained had the adjustment made upon the issuance of such Purchase Right been made upon the basis of the issuance of only the number of shares of Common Stock actually issued upon the exercise of such Purchase Rights. 

(iv) If the number of shares of Common Stock outstanding at any time after the date this Certificate of Incorporation is filed with the
Secretary of State of the State of Delaware (the “Filing Date”) is increased by a stock dividend payable in shares of Common Stock or by a subdivision or split-up of shares of Common Stock, then, on the date such payment is made or

 
such change is effective, the applicable Conversion Price shall be appropriately decreased so that the number of shares of Common Stock issuable on conversion of any shares of such Preferred
Stock shall be increased in proportion to such increase of outstanding shares. 
 (v) If the number of shares of Common Stock outstanding at
any time after the Filing Date is decreased by a combination of the outstanding shares of Common Stock then, on the effective date of such combination, the applicable Conversion Price shall be appropriately increased so that the number of shares of
Common Stock issuable on conversion of any shares of Preferred Stock shall be decreased in proportion to such decrease in outstanding shares. 

(vi) In case this corporation shall declare a cash dividend upon its Common Stock payable otherwise than out of retained earnings or shall
distribute to holders of its Common Stock shares of its capital stock (other than Common Stock), stock or other securities of other persons, evidences of indebtedness issued by this corporation or other persons, assets (excluding cash dividends) or
options or rights (excluding Purchase Rights), then, in each such case, the holders of shares of Preferred Stock shall, concurrent with the distribution to holders of Common Stock, receive a like distribution based upon the number of shares of
Common Stock into which each series of Preferred Stock is convertible. 
 (vii) In case, at any time after the date hereof, of any capital
reorganization, or any reclassification of the stock of this corporation (other than as a result of a stock dividend or subdivision, split-up or combination of shares provided for under Section 4(e)(iv) or (v) above), or the
consolidation or merger of this corporation with or into another person (other than a consolidation or merger in which this corporation is the continuing entity and which does not result in any change in the Common Stock), or of the sale or other
disposition of all or substantially all the properties and assets of this corporation (“Transaction”), the shares of Preferred Stock shall, after such Transaction, be convertible into the kind and number of shares of stock or other
securities or property of this corporation or otherwise to which such holder would have been entitled if immediately prior to such Transaction the holder had converted the holder’s shares of Preferred Stock into Common Stock. The provisions of
this clause (vii) shall similarly apply to successive Transactions. 
 (viii) All calculations under this Section 4 shall be
made to the nearest cent or to the nearest 1/100 of a share, as the case may be. 
 (ix) For the purpose of any computation pursuant to this
Section 4(e), the “Current Market Price” at any date of one share of Common Stock, shall be deemed to be the average of the highest reported bid and the lowest reported offer prices on the preceding business day as
reported by Nasdaq (or equivalent recognized source of quotations); provided, however, that if the Common Stock is not traded in such manner that the quotations referred to in this clause (ix) are available for the period required hereunder,
Current Market Price shall be determined in good faith by the board of directors of this corporation. 
 (f) Minimal Adjustments. No
adjustment in the Conversion Price need be made if such adjustment would result in a change in the Conversion Price of less than $0.01. Any adjustment of less than $0.01 which is not made shall be carried forward and shall be made at the time of and
together with any subsequent adjustment which, on a cumulative basis, amounts to an adjustment of $0.01 or more in the Conversion Price. 

 (g) Conversion Price of Series A-1 Preferred Stock. From and after such time as any
share of Series A-1 Preferred Stock is issued and outstanding, the Conversion Price for the Series A-1 Preferred Stock shall be the Series A Conversion Price in effect immediately prior to such issuance and shall not thereafter be subject to
adjustment pursuant to Section 4(e) hereof 
 (h) Certificate as to Adjustments. Upon the occurrence of each
adjustment or readjustment of the Conversion Rate pursuant to this Section 4, this corporation at its expense shall promptly compute such adjustment or readjustment in accordance with the terms hereof and prepare and furnish to each
holder of Preferred Stock a certificate setting forth such adjustment or readjustment and showing in detail the facts upon which adjustment or readjustment is based. This corporation shall, upon request at any time of any holder of Preferred Stock,
furnish or cause to be furnished to such holder a like certificate setting forth (i) such adjustments and readjustments, (ii) the Conversion Rate at the time in effect, and (iii) the number of shares of Common Stock and the amount, if
any, of other property which at the time would be received upon the conversions of such holder’s shares of Preferred Stock. 

(i) Notices of Record Date. In the event of any taking by this corporation of a record of the holders of any class of securities
for the purpose of determining the holders thereof who are entitled to receive any dividend (other than a cash dividend) or other distribution, any right to subscribe for, purchase or otherwise acquire any shares of stock of any class or any other
securities or property or to receive any other right, this corporation shall mail to each holder of Preferred Stock at least twenty (20) days prior to such record date, a notice specifying the date on which any such record is to be taken for
the purpose of such dividend or distribution or right, and the amount and character of such dividend, distribution or right. 
 (j)
Reservation of Stock Issuable Upon Conversion. This corporation shall at all times reserve and keep available out of its authorized but unissued shares of Common Stock solely for the purpose of effecting the conversion of the shares of
Preferred Stock such number of its shares of Common Stock as shall from time to time be sufficient to effect the conversion of all outstanding shares of Preferred Stock; and if at any time the number of authorized but unissued shares of Common Stock
shall not be sufficient to effect the conversion of all then outstanding shares of Preferred Stock, this corporation will take such corporate action as may, in the opinion of its counsel, be necessary to increase its authorized but unissued shares
of Common Stock to such number of shares as shall be sufficient for such purpose. 
 (k) Notices. Any notice required by the
provisions of this Section 4 to be given to the holder of shares of Preferred Stock shall be deemed given if deposited in the United States mail, postage prepaid, and addressed to each holder of record at such holder’s address
appearing on the books of this corporation. 
 5. Special Mandatory Conversions. 

(a) At any time following the date upon which any shares of Series A Preferred Stock were first issued, if (i) any holder of shares of
Series A Preferred Stock is entitled to exercise the right of first offer (the “Right of First Offer”) as set forth in Section 3.1 of that certain Investors’ Rights Agreement, dated as of March 30, 2007, among
this corporation and the holders of the Series A Preferred Stock, as such agreement may from time to time be amended (the “Agreement”), with respect to an equity financing of this corporation in which the purchase price is less than
Ninety-One Cents ($0.91) per share (as adjusted for stock splits, stock 

 
dividends, recapitalization and similar events) (which shall not include shares of Series A Preferred Stock offered by this corporation at the Subsequent Closing, as that term is defined in the
Series A Preferred Stock and Warrant Purchase Agreement, dated on or about January 22, 2010, by and among this corporation and the parties thereto (the “Purchase Agreement”)) (an “Equity Financing”),
(ii) this corporation has complied with its obligations under the Agreement with respect to the Right of First Offer, (iii) the terms of this Section 5(a) are not waived in writing by the holders of at least sixty percent
(60%) of the outstanding shares of Series A Preferred Stock in connection with such Equity Financing and (iv) such holder does not by exercise of such holder’s Right of First Offer acquire the minimum amount of Offered Securities
(defined below) to which such holder is entitled pursuant to Section 3.1 of the Agreement or such lesser amount of securities (the “Threshold Amount”) agreed to in writing by this corporation and holders of at least
sixty percent (60%) of the outstanding shares of Series A Preferred Stock (excluding for this purpose any shares held by such holder), then all of such holder’s shares of Series A Preferred Stock shall automatically and without further
action on the part of such holder be converted into an equivalent number of shares of Series A-1 Preferred Stock effective immediately prior to the consummation of such Equity Financing. “Offered Securities” means the equity
securities of this corporation set aside by the board of directors of this corporation for purchase by holders of outstanding shares of Series A Preferred Stock in connection with an Equity Financing, and offered to such holders. For purposes of
this Section 5(a), a holder and its Affiliates (as defined in the Agreement) shall, at the election of such holder, be treated as an Investor Group (as defined in the Agreement) and may reallocate the Right of First Offer among themselves as
they determine. Notwithstanding the foregoing, to the extent that a holder purchases some securities in an Equity Financing but not an amount equal to the Threshold Amount, only a Pro-rata Portion (as defined below) of such holder’s shares
shall be converted into shares of Series A-1 Preferred Stock. “Pro-rata Portion” shall be equal to the percent of such holder’s Threshold Amount the holder does not purchase. The conversion provided for in this
Section 5(a) shall not occur in connection with a particular Equity Financing if, pursuant to the written request of this corporation, the Right of First Offer with respect to such Equity Financing is waived in accordance with the terms
of the Agreement. Upon conversion pursuant to this Section 5, the shares of Series A Preferred Stock so converted shall be canceled and not subject to reissuance. 

(b) At any time following the filing and acceptance of this Amended and Restated Certificate of Incorporation, if any holder of more than one
percent (1%) of the outstanding Preferred Stock (a “Major Preferred Stockholder”) does not (either individually or through its affiliates) fund any portion of its Required Initial Closing Pro Rata Share (as defined in 2011 Note
and Warrant Purchase Agreement) at the Initial Closing (as defined in 2011 Note and Warrant Purchase Agreement) (a “Non-Participating Initial Closing Holder”) pursuant to the 2011 Note and Warrant Purchase Agreement, then a
proportionate share of such Non-Participating Initial Closing Holder’s shares of Preferred Stock equal to any such deficiency shall automatically and without further action on the part of such Non-Participating Initial Closing Holder be,
effective immediately prior to, but subject to, the consummation of the Initial Closing, converted into Common Stock at the then effective Conversion Price for each series of Preferred Stock held by such Non-Participating Initial Closing Holder.
Upon conversion pursuant to this Section 5(b), the shares of Preferred Stock so converted shall be cancelled and not subject to reissuance. 

 (c) At any time following the filing and acceptance of this Amended and Restated Certificate of
Incorporation, if any Major Preferred Stockholder does not (either individually or through its affiliates) fund any portion of its Required Additional Closing Pro Rata Share (as defined in 2011 Note and Warrant Purchase Agreement) at the Additional
Closing (as defined in 2011 Note and Warrant Purchase Agreement) (a “Non-Participating Additional Closing Holder”) pursuant to the 2011 Note and Warrant Purchase Agreement, then a proportionate share of such Non-Participating
Additional Closing Holder’s shares of Preferred Stock equal to any such deficiency shall automatically and without further action on the part of such Non-Participating Additional Closing Holder be, effective immediately prior to, but subject
to, the consummation of the Additional Closing, converted into Common Stock at the then effective Conversion Price for each series of Preferred Stock held by such Non-Participating Additional Closing Holder. Upon conversion pursuant to this
Section 5(c), the shares of Preferred Stock so converted shall be cancelled and not subject to reissuance. 
 (d) The holder of
any shares of Preferred Stock converted pursuant to Section 5(a), Section 5(b) or Section 5(c) hereof shall deliver to this corporation during regular business hours at the office of any transfer agent of this
corporation for such series of Preferred Stock, or at such other place as may be designated by this corporation, the certificate or certificates representing the shares so converted, duly endorsed or assigned in blank or to this corporation, or a
reasonably acceptable affidavit and indemnity undertaking in the case of a lost, stolen or destroyed certificate. As promptly thereafter as is practicable, this corporation shall issue and deliver to such holder, at the place designated by such
holder, a certificate or certificates for the number of full shares of the Series A-1 Preferred Stock or Common Stock to which such holder is entitled pursuant to Section 5(a), Section (b) or Section 5(c) hereof,
as applicable. The person in whose name the certificate for such shares of Series A-1 Preferred Stock or Common Stock, as applicable, is to be issued shall be deemed to have become a stockholder on the effective date of the conversion of the
Preferred Stock, unless the transfer books of this corporation are closed on that date, in which case such person shall be deemed to have become a stockholder of record on the next succeeding date on which the transfer books are open. 

(d) This corporation shall not issue any shares of Series A-1 Preferred Stock except pursuant to and in accordance with this Section 5.

 6. Protective Provisions. So long as at least One Million (1,000,000) shares of Preferred Stock are outstanding, this
corporation shall not (by merger, reclassification or otherwise), without first obtaining the approval (by vote or written consent, as provided by law) of the holders of at least sixty percent (60%) of the then outstanding shares of Preferred
Stock voting as a single class: 
 (a) amend the Certificate of Incorporation or Bylaws to alter or change the rights, preferences or
privileges of the Preferred Stock; 
 (b) increase or decrease the aggregate number of authorized shares of any class of stock; 

 (c) increase the number of shares reserved under any stock option plan of this corporation; 

(d) create or effect a creation of any new class or series of shares of stock; 

(e) effect any (i) Liquidating Transaction or (ii) an agreement for the sale of capital stock such that the stockholders immediately
prior to such sale will possess less than fifty percent (50%) of the voting power immediately after such sale; 
 (f) declare or pay
dividends on any capital stock; 
 (g) execute any action to increase or decrease the number of directors of this corporation; 

(h) repurchase or redeem any shares of capital stock except in connection with the repurchase of shares of Common Stock issued to or held by
employees or consultants upon termination of their employment or services pursuant to agreements providing for the right of said repurchase between this corporation and such persons but only to the extent each repurchase equals the original purchase
price of such shares being repurchased; or 
 (i) do any act or thing which would result in taxation of the holders of shares of the
Preferred Stock under Section 305 of the Internal Revenue Code of 1986, as amended (or any comparable provision of the Internal Revenue Code as hereafter from time to time amended). 

ARTICLE VI 
 This
corporation is to have perpetual existence. 
 ARTICLE VII 

1. Limitation of Liability. To the fullest extent permitted by the General Corporation Law of the State of Delaware as the same exists or as may
hereafter be amended, a director of this corporation shall not be personally liable to this corporation or its stockholders for monetary damages for breach of fiduciary duty as a director. 

2. Indemnification. This corporation may indemnify to the fullest extent permitted by law any person made or threatened to be made a party to an
action or proceeding, whether criminal, civil, administrative or investigative, by reason of the fact that such person or his or her testator or intestate is or was a director, officer or employee of this corporation, or any predecessor of this
corporation, or serves or served at any other enterprise as a director, officer or employee at the request of this corporation or any predecessor to this corporation. 

3. Amendments. Neither any amendment nor repeal of this Article VII, nor the adoption of any provision of this corporation’s
Certificate of Incorporation inconsistent with this Article VII, shall eliminate or reduce the effect of this Article VII, in respect of any matter occurring, or any action or proceeding accruing or arising or that, but for this
Article VII, would accrue or arise, prior to such amendment, repeal, or adoption of an inconsistent provision. 

 ARTICLE VIII 

The shares of Series A Preferred Stock may not be redeemed by this corporation. In the event that the shares of Series A Preferred Stock shall
be converted pursuant to the terms hereof, the shares so converted shall not revert to the status of authorized but unissued shares, but instead shall be canceled and shall not be re-issuable by this corporation. 

ARTICLE IX 
 Holders of
stock of any class or series of this corporation shall not be entitled to cumulate their votes for the election of directors or any other matter submitted to a vote of the stockholders. 

ARTICLE X 
 Elections of
directors need not be by written ballot unless the Bylaws of this corporation so provide. 
 ARTICLE XI 

This corporation hereby renounces, to the fullest extent permitted by Section 122 (17) of the General Corporation Law of the State
of Delaware, any interest or expectancy of this corporation in, or in being offered, an opportunity to participate in, any Series A Business Opportunity. A “Series A Business Opportunity” is any matter, transaction or interest that
is presented to, or acquired, created or developed by, or which otherwise comes into the possession of, (i) any director of this corporation who is not an employee of this corporation or any of its subsidiaries, or (ii) any holder of
Series A Preferred Stock or any partner, member, director, stockholder, employee or agent of any such holder, other than someone who is an employee of this corporation or any of its subsidiaries (collectively, “Covered Persons”),
unless such matter, transaction or interest is presented to, or acquired, created or developed by, or otherwise comes into the possession of, a Covered Person solely in such Covered Person’s capacity as a director of this corporation. To the
fullest extent permitted by law, this corporation hereby waives any claim against a Covered Person, and agrees to indemnify all Covered Persons against any claim, that is based on fiduciary duties, the corporate opportunity doctrine or any other
legal theory which could limit any Covered Person from pursuing or engaging in any Series A Business Opportunity. 
 ARTICLE XII 

In furtherance and not in limitation of the powers conferred by statute, the board of directors of this corporation is expressly authorized to
make, alter, amend or repeal the Bylaws of this corporation. 
 ARTICLE XIII 

The foregoing amendment and restatement of the Certificate of Incorporation has been duly approved by the board of directors of this
corporation. 
 *     *     * 

 The foregoing Fourth Amended and Restated Certificate of Incorporation has been duly adopted by
this corporation’s Board of Directors and stockholders in accordance with applicable provisions of Sections 228, 242 and 245 of the General Corporation Law of the State of Delaware. I further declare under penalty of perjury under the laws of
the State of Delaware that the matters set forth in this certificate are true, correct and of my own knowledge. 
 Dated: December 20, 2011 

 

	
	 /s/ Joanna Horobin

	 Name: Joanna Horobin, M.D.

	 Title: Chief Executive Officer

 Exhibit B 

2012 Charter Amendment 

  
 Exhibit B 

 CERTIFICATE OF AMENDMENT 

TO 
 CERTIFICATE OF
INCORPORATION 
 OF 

SYNDAX PHARMACEUTICALS, INC. 

SYNDAX PHARMACEUTICALS, INC., a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware
(the “Corporation”), DOES HEREBY CERTIFY: 
 FIRST: That resolutions setting forth a proposed amendment to the Fourth
Amended and Restated Certificate of incorporation of the Corporation, declaring said amendment to be advisable and directing that said amendment be considered by the stockholders of the Corporation, were duly adopted by the Board of Directors of the
Corporation, acting by unanimous written consent. 
 SECOND: That said amendment was approved by the stockholders of the Corporation
entitled to vote on such amendment acting by written consent in accordance with the provisions of Section 228 of the General Corporation Law of the State of Delaware. 

THIRD: That said amendment amends the Fourth Amended and Restated Certificate of Incorporation of the Corporation by deleting the existing
Article IV of said Certificate of Incorporation in its entirety and substituting therefore a new Article IV to read in its entirety as follows: 

ARTICLE IV 

This corporation is authorized to issue two classes of stock to be designated, respectively, “Common Stock”
and “Preferred Stock.” The total number of shares which this corporation is authorized to issue is Two Hundred Seventy Million (270,000,000) shares. One Hundred Fourteen Million (114,000,000) shares shall be Common Stock
with a par value of $0.0001 per share and One Hundred Fifty-Six Million (156,000,000) shares shall be Preferred Stock with a par value of $0.001 per share, Seventy-Eight Million (78,000,000) shares of which shall be designated Series A
Preferred Stock (“Series A Preferred Stock”) and Seventy-Eight Million (78,000,000) shares of which shall be designated Series A-1 Preferred Stock (“Series A-1 Preferred Stock” and together with the Series A
Preferred Stock, the “Preferred Stock”). This corporation shall from time to time in accordance with the laws of the State of Delaware increase the authorized amount of its Common Stock if at any time the number of shares of Common
Stock remaining unissued and available for issuance upon conversion of the Preferred Stock shall not be sufficient to permit conversion of the Preferred Stock. Subject to the provisions herein, 

 
the number of authorized shares of Common Stock may be increased or decreased (but not below the number of shares thereof then outstanding) by the affirmative vote of the holders of shares of
stock of this corporation representing a majority of the votes represented by all outstanding shares of stock of this corporation entitled to vote, irrespective of the provisions of Section 242(b)(2) of the Delaware General Corporation Law.

 FOURTH: That said amendment was duly adopted in accordance with the applicable provisions of Sections 242 and 228 of the General
Corporation Law of the State of Delaware. 
 [SIGNATURE PAGE FOLLOWS] 

 IN WITNESS WHEREOF, the Corporation has caused this Certificate of Amendment to be executed by
Arlene M. Morris, its Chief Executive Officer, this 28th day of June, 2012. 
  

			
	 SYNDAX PHARMACEUTICALS, INC.

		
	By:	 	/s/ Arlene M. Morris
	Name:	 	Arlene M. Morris
	Title:	 	Chief Executive Officer

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