Introductory Note
On September 29, 2026, Lexeo Therapeutics, Inc. (“Lexeo” or the “Company”) completed the previously announced acquisition of Mantle Therapeutics Inc. (“Mantle”), pursuant to the Agreement and Plan of Merger dated September 16, 2026 (the “Merger Agreement”) by and among the Company, Mantle and Magma Merger Sub Inc., a Delaware corporation and a wholly-owned subsidiary of the Company (“Merger Sub”), and Shareholder Representative Services LLC, a Colorado limited liability company, solely in its capacity as representative, agent and attorney in fact of the Sellers. Pursuant to the Merger Agreement, Merger Sub was merged with and into Mantle (the “Merger”), with Mantle continuing as the surviving corporation and wholly owned subsidiary of Lexeo.
The descriptions of the Merger Agreement and the transactions contemplated thereby (including, without limitation, the Merger) in this Current Report on Form 8-K are only a summary, do not purport to be complete and are subject to, and qualified in their entirety by reference to, the full text of the Merger Agreement, a copy of which was filed as Exhibit 2.1 to the Company’s Current Report on Form 8-K filed with the Securities and Exchange Commission (the “SEC”) on September 22, 2026, which is incorporated herein by reference.
Item 2.01 Completion of Acquisition or Disposal of Assets.
At the effective time of the Merger (the “Effective Time”), each outstanding share of Mantle capital stock (other than shares held by Mantle as treasury shares, shares held by Lexeo or Merger Sub, and Dissenting Shares) was converted into the right to receive an aggregate upfront purchase price consisting of: (i) $5,300,000 in cash, subject to certain adjustments; and (ii) $3,000,000 in shares of Lexeo common stock, par value $0.0001 per share (the "Common Stock"). The Common Stock issued at the Effective Time is not being registered under the Securities Act of 1933, as amended (the "Securities Act"), or any state securities laws, and is issued in reliance on the exemption from registration provided by Section 4(a)(2) under the Securities Act and/or Regulation D promulgated thereunder for transactions not involving a public offering.
Immediately prior to the Effective Time, each outstanding share of Mantle restricted stock vested in full and was cancelled in exchange for the right to receive the same consideration as each share of Mantle capital stock above, subject to withholding. Immediately prior to the Effective Time, each outstanding simple agreement for future equity ("SAFE") of Mantle was cancelled in exchange for the applicable SAFE consideration, determined in accordance with the liquidity event provisions of each SAFE. Each outstanding convertible promissory note of Mantle was cancelled upon payment of the payoff amount determined under the Merger Agreement.
In addition to the consideration payable at closing, the Merger Agreement provides for the following contingent payments, none of which is guaranteed and each of which may never become payable:
•Additional Cash Payment. An additional one-time aggregate cash payment of $1,000,000, payable only upon the achievement of certain events.
•Milestone Payments. Up to an aggregate of $12,000,000 payable upon the achievement of specified development and regulatory milestones relating to Mantle’s product candidates, over a milestone term of 12 years. Certain of the milestone payments are payable in cash, and certain of the milestone payments are payable in shares of Common Stock valued using a thirty-day trailing volume-weighted average price based on the date of achievement such milestone.
Lexeo makes no guarantees that it will achieve any milestone, and the Merger Agreement does not require Lexeo to devote any particular level of resources to the development or commercialization of Mantle’s product candidates beyond the commercially reasonable efforts standard set forth in the Merger Agreement.
Item 3.02 Unregistered Sales of Equity Securities.
The information set forth in Item 2.01 of this Current Report on Form 8-K regarding the issuance of shares of the Company’s Common Stock in connection with the Merger is incorporated herein by reference.
The shares of Common Stock issued in connection with the Merger were not registered under the Securities Act of 1933, or any applicable state securities laws and were issued in reliance on the exemption from registration provided by Section 4(a)(2) of the Securities Act and/or Regulation D promulgated thereunder.
