UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 10-Q/A

(Mark One)

☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended March 31, 2025

OR

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from to

Commission file number: 001-41855

Lexeo Therapeutics, Inc.

(Exact Name of Registrant as Specified in its Charter)

(212) 547-9879

(Registrant’s telephone number, including area code)

N/A

(Former name, former address and former fiscal year, if changed since last report)

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

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒

The Registrant had 33,196,997 shares of common stock outstanding as of May 12, 2025.

EXPLANATORY NOTE

Lexeo Therapeutics, Inc. (the “Company”) is filing this Amendment No. 1 to the Quarterly Report on Form 10-Q/A (this “Amendment”) to amend its Quarterly Report on Form 10-Q for the fiscal quarter ended March 31, 2025 filed with the Securities and Exchange Commission (the “SEC”) on May 12, 2025 (the “Original Filing”). This Amendment is being filed solely for the purpose of updating Exhibits 31.1 and 31.2. The original exhibits inadvertently omitted certain language regarding management’s responsibility for establishing and maintaining internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)), and having designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of our financial statements for external purposes in accordance with generally accepted accounting principles.

Except for the foregoing, the Original Filing remains unchanged. This Amendment does not reflect any events occurring after the filing of the Original Filing nor does it modify or otherwise update in any way disclosures made in the Original Filing. No revisions are being made to the Company’s financial statements or any other disclosure contained in the Original Filing. Accordingly, this Amendment should be read in conjunction with the Company’s filings made with the SEC subsequent to the filing of the Original Filing, including any amendment to those filings.

Item 6. Exhibits.

The following exhibits are filed as part of this report:

* Filed herewith

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 thereunto duly authorized.