Material Event (Form 8-K)

Item 8.01 Other Events.

In connection with Cabaletta Bio's (the "Corporation") June 2025 underwritten public offering, the Corporation issued 53,090,190 common stock warrants (the "Common Stock Warrants") that had an exercise price of $2.50 per whole share of its common stock and an expiration date of September 12, 2026 (the "Expiration Date").

From issuance through June 30, 2026, 5,275,100 Common Stock Warrants were exercised resulting in aggregate gross proceeds of approximately $13.2 million. From July 1, 2026 through the Expiration Date, 46,011,900 Common Stock Warrants were exercised resulting in aggregate gross proceeds of approximately $115.0 million. The aggregate gross proceeds from exercises of the Common Stock Warrants from issuance through the Expiration Date is approximately $128.2 million.