8-K

UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Lexeo Therapeutics, Inc.

(Exact name of Registrant as Specified in Its Charter)

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On January 30, 2026, Lexeo Therapeutics, Inc. (the “Company”) entered into a Transition and Consulting Agreement (the “Transition Agreement”) with Dr. Adler, effective February 1, 2026, pursuant to which Dr. Adler stepped down from his role of Head of Research and will continue to provide certain advisory services to the Company until the earlier of (i) July 31, 2026 and (ii) termination of the Transition Agreement by the Company or Dr. Adler (the “Transition Period”). During the Transition Period, Dr. Adler will receive up to a total of $62,500, to be paid in monthly installments, and his service-vesting equity awards will continue to vest during this period as compensation for his services. Pursuant to the terms of the Transition Agreement, Dr. Adler’s last day to exercise any vested stock options will be extended until the day that is six (6) months following the end of the Transition Period. The Transition Agreement includes customary release of claims, non-disparagement, and cooperation provisions in favor of the Company, as well as other customary provisions. Dr. Adler will also receive a lump sum payment of $1,000 in the event that, following the Transition Period, he executes and delivers a supplemental release of claims in favor of the Company.

The foregoing summary of the Transition Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Transition Agreement, a copy of which the Company plans to file as an exhibit to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.