Amendment: SEC Form SCHEDULE 13D/A filed by Adicet Bio Inc.

601 Lexington Avenue, 54th Floor, New York, New York 10022.

Advisors is the managing member or general partner of certain entities as more particularly described in Item 6 below. GP V is the general partner of a limited partnership as more particularly described in Item 6 below. GP VI is the general partner of a limited partnership as more particularly described in Item 6 below. Genesis GP is the general partner of a limited partnership as more particularly described in Item 6 below. BioFund is the general partner of a limited partnership as more particularly described in Item 6 below. Israel GP Ltd. is the general partner of BioFund. Israel GP II is the general partner of a limited partnership as more particularly described in Item 6 below. Israel II Limited is the general partner of Israel GP II. Gordon is a member of OrbiMed Advisors, a member of the management and investment committees of certain entities as more particularly described in Item 5 below. Chimovits is a member of the investment committees of certain entities as more particularly described in Item 5 below. Sven H. Borho is a member of OrbiMed Advisors. W. Carter Neild is a member of OrbiMed Advisors. Geoffrey C. Hsu is a member of OrbiMed Advisors. C. Scotland Stevens is a member of OrbiMed Advisors. David P. Bonita is a member of OrbiMed Advisors. Peter A. Thompson is a member of OrbiMed Advisors. Matthew S. Rizzo is a member of OrbiMed Advisors. Mona Ashiya is a member of OrbiMed Advisors. Trey Block is the Chief Financial Officer of OrbiMed Advisors.

Not applicable.

Not applicable.

Item 2(a) is incorporated herein by reference.

Not applicable.

The Reporting Persons from time to time intend to review their investment in the Issuer on the basis of various factors, including the Issuer's business, financial condition, results of operations and prospects, general economic and industry conditions, the securities markets in general and those for the Issuer's Shares in particular, as well as other developments and other investment opportunities. Based upon such review, the Reporting Persons will take such actions in the future as the Reporting Persons may deem appropriate in light of the circumstances existing from time to time. If the Reporting Persons believe that further investment in the Issuer is attractive, whether because of the market price of Shares or otherwise, they may acquire Shares or other securities of the Issuer either in the open market or in privately negotiated transactions. Similarly, depending on market and other factors, the Reporting Persons may determine to dispose of some or all of the Shares currently owned by the Reporting Persons or otherwise acquired by the Reporting Persons either in the open market or in privately negotiated transactions. Except as set forth in this Schedule 13D, the Reporting Persons have not formulated any plans or proposals which relate to or would result in: (a) the acquisition by any person of additional securities of the Issuer or the disposition of securities of the Issuer, (b) an extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries, (c) a sale or transfer of a material amount of the assets of the Issuer or any of its subsidiaries, (d) any change in the present Board of Directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board, (e) any material change in the Issuer's capitalization or dividend policy of the Issuer, (f) any other material change in the Issuer's business or corporate structure, (g) any change in the Issuer's charter or bylaws or other instrument corresponding thereto or other action which may impede the acquisition of control of the Issuer by any person, (h) causing a class of the Issuer's securities to be deregistered or delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association, (i) a class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Act or (j) any action similar to any of those enumerated above.

The following disclosure is based upon 153,253,530 Shares outstanding of the Issuer as set forth in the Issuer's Rule 424(b)(5) Prospectus filed with the SEC on October 7, 2025. As of the date of this filing, OPI V, a limited partnership organized under the laws of Delaware, holds 9,026,359 Shares, constituting approximately 5.9% of the issued and outstanding Shares. GP V is the general partner of OPI V, pursuant to the terms of the limited partnership agreement of OPI V, and Advisors is the managing member of GP V, pursuant to the terms of the limited liability company agreement of GP V. As a result, Advisors and GP V share power to direct the vote and disposition of the Shares held by OPI V and may be deemed directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares held by OPI V. Advisors exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the Shares held by OPI V. As of the date of this filing, OPI VI, a limited partnership organized under the laws of Delaware, holds 4,490,254 Shares, constituting approximately 2.9% of the issued and outstanding Shares. GP VI is the general partner of OPI VI, pursuant to the terms of the limited partnership agreement of OPI VI, and Advisors is the managing member of GP VI, pursuant to the terms of the limited liability company agreement of GP VI. As a result, Advisors and GP VI share power to direct the vote and disposition of the Shares held by OPI VI and may be deemed directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares held by OPI VI. Advisors exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the Shares held by OPI VI. As of the date of this filing, OrbiMed Genesis Master Fund, L.P. ("Genesis"), a limited partnership organized under the laws of the Cayman Islands, holds 1,255,985 Shares, constituting approximately 0.8% of the issued and outstanding Shares. Genesis GP is the general partner of Genesis, pursuant to the terms of the limited partnership agreement of Genesis, and Advisors is the managing member of Genesis GP, pursuant to the terms of the limited liability company agreement of Genesis GP. As a result, Advisors and Genesis GP share power to direct the vote and disposition of the Shares held by Genesis and may be deemed, directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares held by Genesis. Advisors exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho and W. Carter Neild, each of whom disclaims beneficial ownership of the Shares held by Genesis. As of the date of this filing, OrbiMed Israel Partners Limited Partnership ("OIP"), a limited partnership organized under the laws of Israel, holds 1,027,885 Shares, constituting approximately 0.7% of the issued and outstanding Shares. BioFund is the general partner of OIP, pursuant to the terms of the limited partnership agreement of OIP, and Israel GP Ltd. is the general partner of BioFund, pursuant to the terms of the limited partnership agreement of BioFund. As a result, BioFund and Israel GP Ltd. share the power to direct the vote and disposition of the Shares held by OIP and may be deemed, directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares held by OIP. Israel GP Ltd. exercises this investment power through an investment committee comprised of Carl L. Gordon and Erez Chimovits, each of whom disclaims beneficial ownership of the Shares held by OIP. As of the date of this filing, OrbiMed Israel Partners II, L.P. ("OIP II"), a limited partnership organized under the laws of the Cayman Islands, holds 646,657 Shares, constituting approximately 0.4% of the issued and outstanding Shares. Israel GP II is the general partner of OIP II, pursuant to the terms of the limited partnership agreement of OIP II, and Israel II Limited is the general partner of Israel GP II, pursuant to the terms of the limited partnership agreement of Israel GP II. As a result, Israel GP II and Israel II Limited share the power to direct the vote and disposition of the Shares held by OIP II and may be deemed, directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares held by OIP II. Israel II Limited exercises this investment power through an investment committee comprised of Carl L. Gordon, David Bonita, and Erez Chimovits, each of whom disclaims beneficial ownership of the Shares held by OIP II.

Item 5(a) is incorporated by reference herein.

On October 8, 2025, OPI V purchased 1,500,000 Shares at a price of $1.00 per Share. On October 8, 2025, OPI VI purchased 3,500,000 Shares at a price of $1.00 per Share. The Reporting Persons undertake, upon request by the staff of the SEC or the Issuer to provide full information regarding the number of Shares sold at each separate price.

Not applicable.

Not applicable.

In addition to the relationships between the Reporting Persons described in Items 2 and 5 above, GP V is the general partner of OPI V, pursuant to the terms of the limited partnership agreement of OPI V. Pursuant to this agreement and relationship, GP V has discretionary investment management authority with respect to the assets of OPI V. Such authority includes the power to vote and otherwise dispose of securities held by OPI V. The number of outstanding Shares attributable to OPI V is 9,026,359 Shares. GP V, pursuant to its authority under the limited partnership agreement of OPI V, may be considered to hold indirectly 9,026,359 Shares. In addition to the relationships between the Reporting Persons described in Items 2 and 5 above, GP VI is the general partner of OPI VI, pursuant to the terms of the limited partnership agreement of OPI VI. Pursuant to this agreement and relationship, GP VI has discretionary investment management authority with respect to the assets of OPI VI. Such authority includes the power to vote and otherwise dispose of securities held by OPI VI. The number of outstanding Shares attributable to OPI VI is 4,490,254 Shares. GP VI, pursuant to its authority under the limited partnership agreement of OPI VI, may be considered to hold indirectly 4,490,254 Shares. In addition to the relationships between the Reporting Persons described in Items 2 and 5 above, Genesis GP is the general partner of Genesis, pursuant to the terms of the limited partnership agreement of Genesis. Pursuant to this agreement and relationship, Genesis GP has discretionary investment management authority with respect to the assets of Genesis. Such authority includes the power to vote and otherwise dispose of securities held by Genesis. The number of outstanding Shares attributable to Genesis is 1,255,985 Shares. Genesis GP, pursuant to its authority under the limited partnership agreement of Genesis, may be considered to hold indirectly 1,255,985 Shares. In addition to the relationships between the Reporting Persons described in Items 2 and 5 above, Advisors is the managing member of GP V, GP VI, and Genesis GP, pursuant to the terms of the limited liability company agreements of GP V, GP VI, and Genesis GP. Pursuant to these agreements and relationships, Advisors and GP V have discretionary investment management authority with respect to the assets of OPI V, Advisors and GP VI have discretionary investment management authority with respect to the assets of OPI VI, and Advisors and Genesis GP have discretionary investment management authority with respect to the assets of Genesis. Such authority includes the power of GP V to vote and otherwise dispose of securities held by OPI V, GP VI to vote and otherwise dispose of the securities held by OPI VI, and Genesis GP to vote and otherwise dispose of the securities held by Genesis. The number of outstanding Shares attributable to OPI V is 9,026,359 Shares, the number of outstanding Shares attributable to OPI VI is 4,490,254 Shares, and the number of outstanding Shares attributable to Genesis is 1,255,985 Shares. Advisors, pursuant to its authority under the terms of the limited liability company agreements of GP V, GP VI, and Genesis GP may also be considered to hold indirectly 14,772,598 Shares. In addition to the relationships between the Reporting Persons described in Items 2 and 5 above, BioFund is the general partner of OIP, pursuant to the terms of the limited partnership agreement of OIP. Israel GP Ltd. is the general partner of BioFund, pursuant to the terms of the limited partnership agreement of BioFund. Pursuant to these agreements and relationships, Israel GP Ltd. and BioFund have discretionary investment management authority with respect to the assets of OIP. Such authority includes the power of BioFund to vote and otherwise dispose of securities held by OIP. The number of outstanding Shares attributable to OIP is 1,027,885 Shares. BioFund, pursuant to its authority under the limited partnership agreement of OIP, and Israel GP Ltd., pursuant to its authority under the limited partnership agreement of BioFund, may each be considered to hold indirectly 1,027,885 Shares. In addition to the relationships between the Reporting Persons described in Items 2 and 5 above, Israel GP II is the general partner of OIP II, pursuant to the terms of the limited partnership agreement of OIP II. Israel II Limited is the general partner of Israel GP II, pursuant to the terms of the limited partnership agreement of Israel GP II. Pursuant to these agreements and relationships, Israel II Limited and Israel GP II have discretionary investment management authority with respect to the assets of OIP II. Such authority includes the power of Israel GP II to vote and otherwise dispose of securities purchased by OIP II. The number of outstanding Shares attributable to OIP II is 646,657. Israel GP II, pursuant to its authority under the limited partnership agreement of OIP II, and Israel II Limited, pursuant to its authority under the limited partnership agreement of Israel GP II, may each be considered to hold indirectly 646,657 Shares.

Exhibit Description 1. Joint Filing Agreement between OrbiMed Advisors LLC, OrbiMed Capital GP V LLC, OrbiMed Capital GP VI LLC, OrbiMed Genesis GP LLC, OrbiMed Israel GP Ltd., OrbiMed Israel BioFund GP Limited Partnership, OrbiMed Advisors Israel II Limited, and OrbiMed Israel GP II, L.P.