Material Agreement (Form 8-K)

Item 1.01 Entry into a Material Definitive Agreement.

On October 7, 2025, Adicet Bio, Inc. (the Company) entered into an Underwriting Agreement (the Underwriting Agreement) with Jefferies LLC and Guggenheim Securities, LLC, as representatives of the several underwriters listed on Schedule A thereto (the Underwriters), related to an underwritten registered direct offering (the Offering) of 70,001,000 shares (the Shares) of common stock of the Company, par value $0.0001 per share (the Common Stock), and, in lieu of Common Stock to an investor, pre-funded warrants (the Pre-Funded Warrants) to purchase 10,000,000 shares of Common Stock (the Warrant Shares). The Shares are being sold at a price of $1.00 per share and the Pre-Funded Warrants are being sold at a price of $0.9999 per underlying share, which represents the per share price of each share of common stock minus the $0.0001 per share exercise price for each pre-funded warrant. The purchase price to be paid by the Underwriters to the Company will be $0.94 per Share and $0.93991 per Pre-Funded Warrant, representing a discount to the Underwriters of 6.0%. The Company estimates net proceeds from the Offering, after deducting the underwriting discount and commissions and other estimated offering expenses, will be approximately $74.8 million. The Company may receive nominal proceeds, if any, from the exercise of the Pre-Funded Warrants. The Offering is expected to close on October 8, 2025.

Each Pre-Funded Warrant has an exercise price of $0.0001 per share. The exercise price and the number of shares of Common Stock issuable upon exercise of each Pre-Funded Warrant is subject to appropriate adjustments in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting the Common Stock. Each Pre-Funded Warrant is exercisable from the date of issuance by means of a cashless exercise. Under the Pre-Funded Warrants, the Company may not effect the exercise of any Pre-Funded Warrant, and a holder will not be entitled to exercise any portion of any Pre-Funded Warrant that, upon giving effect to such exercise, would cause: (i) the aggregate number of shares of Common Stock beneficially owned by the holder (together with its affiliates) to exceed 9.99% of the number of shares of Common Stock outstanding immediately after giving effect to the exercise, or (ii) the combined voting power of the Company's securities beneficially owned by the holder (together with its affiliates) to exceed 9.99% of the combined voting power of all of the Company's securities then outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Pre-Funded Warrants, unless such percentage is increased upon at least 61 days' prior notice, but not in excess of 19.99%.

In addition, in certain circumstances, upon a fundamental transaction, a holder of Pre-Funded Warrants will be entitled to receive, upon exercise of the Pre-Funded Warrants, the kind and amount of securities, cash or other property that such holder would have received had they exercised the Pre-Funded Warrants immediately prior to the fundamental transaction; provided, however, that in the event of a fundamental transaction where the consideration consists solely of cash, solely of marketable securities or a combination thereof, each Pre-Funded Warrant will be deemed to be exercised in full in a cashless exercise effective immediately prior to and contingent upon the consummation of such fundamental transaction.

The Company made certain customary representations, warranties and covenants concerning the Company and the registration statement in the Underwriting Agreement and also agreed to indemnify the Underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended (the Securities Act). The Offering was made pursuant to the Company's shelf registration statement on Form S-3 (File No. 333-285609), filed with the Securities and Exchange Commission (the Commission) on March 6, 2025, as amended, and declared effective by the Commission on March 14, 2025, as supplemented by a final prospectus supplement, dated October 7, 2025 and filed with the Commission on October 7, 2025 (the Prospectus Supplement). This Current Report on Form 8-K does not constitute an offer to sell or the solicitation of an offer to buy any of the shares of Common Stock or the Pre-Funded Warrants.

The foregoing description of certain terms of the Underwriting Agreement and the transactions contemplated thereby does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Underwriting Agreement, which is filed as Exhibit 1.1 to this Current Report on Form 8-K and is incorporated by reference herein.

The foregoing description of certain terms of the form of Pre-Funded Warrant does not purport to be a complete statement of the rights and obligations of the parties thereto and the transactions contemplated thereby, and is qualified in its entirety by reference to the form of Pre-Funded Warrant, which is filed as Exhibit 4.1 to this Current Report on Form 8-K and is incorporated herein by reference.

A copy of the legal opinion of Goodwin Procter LLP, relating to the legality of the issuance and sale of the shares of Common Stock and the Pre-Funded Warrants in this Offering, is filed as Exhibit 5.1 to this Current Report on Form 8-K and is incorporated by reference herein.