Amendment No. 3, dated February 11, 2024, to the First License Agreement, dated May 28, 2020, by and between LEXEO Therapeutics, Inc. and Cornell University (as amended by Amendment No. 1 to the First License Agreement, dated July 4, 2022 and Amendment No. 2 to the First License Agreement, dated September 28, 2022)

Exhibit 10.21

		Center for Technology Licensing 1155 York Avenue New York, NY 10065 P: 646 ###-###-#### innovation.weill.cornell.edu

February 11, 2024

Jenny Robertson

Chief Business and Legal Officer

Lexeo Therapeutics, Inc.

345 Park Avenue South, 6th Floor

New York, NY 10010

Via email: ***@***

RE: THIRD AMENDMENT

to the FIRST LICENSE AGREEMENT by and between Lexeo Therapeutics, Inc. (hereinafter “Licensee”) and Cornell University (“Cornell”) (each a “Party”) effective May 28, 2020 and amended a first time effective July 4, 2022 and a second time effective September 28, 2022 (Cornell Contract C2020-11-13204) (the “First License Agreement”)

Effective the date of the last signature hereto (“Amendment Date”), the Parties agree to hereby modify the First License Agreement as follows:

1) Appendix A: Inventions is hereby amended to include:

2) Appendix B1: Patent Rights is hereby amended to include:

3) The lists of dockets on the cover page and in the Notices section of the First License Agreement shall include “D-10699”.

4) The lead paragraph in Paragraph 3.3(a)(iii) is hereby amended to read:

(iii) develop a Licensed Product based on Cornell Dockets D-9134, or D-10405, D-10699, or IND 018406 (“Portfolio APOE”) as follows, wherein each row in the following table is an obligation under this Paragraph 3.3(a)(iii):

; and

5) As consideration for this Amendment, Licensee will pay Cornell an amendment fee of Thirty Thousand Dollars ($30,000.00) within thirty (30) days of the Amendment Date.

6) These changes do not otherwise change the terms and conditions of the First License Agreement.

7) This Amendment may be executed by electronic signatures or by facsimile and in two (2) or more counterparts, each of which shall be deemed an original and all of which together shall constitute but one and the same instrument.

IN WITNESS WHEREOF, both Cornell and Licensee have executed this Amendment by their respective and duly authorized officers on the day and year written.

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