and in Exhibits 99.1 and 99.2 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information set forth under

of this Current Report on Form 8-K is incorporated herein by reference. The Company offered and sold the Notes to certain investors in reliance on the exemption from registration provided by Section 4(a)(2) of the Securities Act of 1933, as amended (the “ Securities Act ”). The Company relied on this exemption from registration based in part on representations made by each investor in the subscription agreements, dated June 3, 2026, between the Company and each investor identified therein. Th…

The filing describes the approval of new equity and stock purchase plans, which are not management changes.

Unregistered Sale of Equity Securities. The information set forth under

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information set forth under

Unregistered Sale of Equity Securities. The information set forth under

Entry into a Material Agreement. Indenture and Notes On June 3, 2026, Syndax Pharmaceuticals, Inc. (the “ Company ”) entered into privately negotiated subscription agreements (the “ Subscription Agreements ”) with certain investors, pursuant to which the Company will issue $250.0 million aggregate principal amount of 2.25% Convertible Senior Notes due 2031 (the “ Notes ”). The Notes will be issued pursuant to an indenture (the “ Indenture ”), between the Company and U.S. Bank Trust Company, N…

and in Exhibits 99.1 and 99.2 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

and in Exhibits 99.1 and 99.2 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Results of Operations and Financial Condition. On January 12, 2026, Syndax Pharmaceuticals, Inc. (the “ Company ”) issued a press release in connection with the Company’s presentation on the same date at the 44th Annual J.P. Morgan Healthcare Conference that contains certain preliminary financial information as of and for the fiscal year ended December 31, 2025. Specifically, the press release states that (i) the Company achieved approximately $44 million and $125 million in preliminary (unau…

and in Exhibits 99.1 and 99.2 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

and in Exhibits 99.1 and 99.2 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Director — William Meury: Mr. Meury resigned from the Board to accept a new role at Incyte Corporation.

Head of Research and Development, Chief Medical Officer — Nicholas A.J. Botwood: Dr. Nicholas A.J. Botwood was appointed as Head of Research and Development, Chief Medical Officer.

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Chief Medical Officer — Catherine Madigan, M.D.: The Chief Medical Officer position was eliminated and Dr. Madigan ceased to serve in the role.

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Entry into a Material Definitive Agreement. On November 4, 2024, Syndax Pharmaceuticals, Inc. (“ Syndax ”) entered into a Purchase and Sale Agreement (the “ Purchase and Sale Agreement ”) with Royalty Pharma Development Funding, LLC (“ Royalty Pharma ”), pursuant to which Royalty Pharma purchased rights to certain revenue streams from net sales of products comprising or containing axatilimab (including Niktimvo™) (collectively, the “ Product ”) by Syndax, its affiliates and its licensees in t…

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Class III member of the Board — Briggs W. Morrison, M.D.: Dr. Morrison resigned from his position as a Class III member of the Board.

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Chief Commercial Officer — Steven Closter: Steve Sabus resigned, and Steven Closter was hired as the new Chief Commercial Officer.

and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any of the Company’s filings under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.