Lexeo completes acquisition of Mantle Therapeutics

Lexeo Therapeutics announced that it completed the previously announced acquisition of Mantle Therapeutics Inc. on September 29, 2026, pursuant to the Agreement and Plan of Merger dated September 16, 2026.¹ Under the merger structure, Merger Sub was merged into Mantle, with Mantle continuing as the surviving corporation and wholly owned subsidiary of Lexeo.¹

At closing, each outstanding share of Mantle capital stock was converted into the right to receive an aggregate upfront purchase price of $5,300,000 in cash, subject to certain adjustments, and $3,000,000 in shares of Lexeo common stock.¹ Mantle restricted stock vested in full and was cancelled for the same consideration, outstanding SAFEs were cancelled in exchange for applicable SAFE consideration, and outstanding convertible promissory notes were cancelled upon payment of the payoff amount under the Merger Agreement.¹

Beyond the closing payment, the deal includes contingent consideration. An additional one-time aggregate cash payment of $1,000,000 is payable only upon achievement of certain events.¹ Up to an aggregate of $12,000,000 in milestone payments is tied to specified development and regulatory milestones over a 12-year term, payable in cash or in shares of common stock valued using a thirty-day trailing volume-weighted average price.¹ Lexeo made no guarantee it will achieve any milestone, and the Merger Agreement does not require the company to devote a particular level of resources to developing or commercializing Mantle's product candidates beyond a commercially reasonable efforts standard.¹

The acquired pipeline, previously disclosed, includes four Mantle programs targeting frataxin restoration in the brain. Separately, LX2006 continues to advance enrollment in the SUNRISE-FA 2 pivotal study, which remains Lexeo's highest operational and capital-allocation priority, with a topline data readout still expected in the second half of 2027.²