Sec Form 4 Filing - GORDON CARL L @ Adicet Bio, Inc. - 2021-02-12

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person GORDON CARL L 2. Issuer Name and Ticker or Trading Symbol Adicet Bio, Inc. [ ACET] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O ADICET BIO, INC., 500 BOYLSTON STREET, 13TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 02/12/2021 (Street) BOSTON, MA02116 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 690,055 I See Footnotes ( 1 ) ( 6 ) Common Stock 02/12/2021 A 420,299 ( 2 ) A $ 13 5,243,259 I See Footnotes ( 3 ) ( 6 ) Common Stock 902,885 I See Footnotes ( 4 ) ( 6 ) Common Stock 02/12/2021 A 104,050 ( 2 ) A $ 13 396,657 I See Footnotes ( 5 ) ( 6 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Num ber of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other GORDON CARL L C/O ADICET BIO, INC. 500 BOYLSTON STREET, 13TH FLOOR BOSTON, MA02116 X X Signatures /s/ Carl L. Gordon 02/18/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )These shares of the Issuer's common stock are held of record by OrbiMed Private Investments VI, LP ("OPI VI"). OrbiMed Capital GP VI LLC ("GP VI") is the general partner of OPI VI, and OrbiMed Advisors LLC ("OrbiMed Advisors"), a registered investment adviser under the Investment Advisors Act of 1940, as amended, is the managing member of GP VI. By virtue of such relationships, GP VI and OrbiMed Advisors may be deemed to have voting and investment power with respect to the securities held by OPI VI noted above and as a result may be deemed to beneficially own such securities for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended (the "Exchange Act"). OrbiMed Advisors exercises this investment and voting power through a management committee comprised of the Reporting Person, Sven H. Borho, and Jonathan T. Silverstein, each of whom disclaims beneficial ownership of the Shares held by OPI VI. ( 2 )These shares of the Issuer's common stock were purchased in a private placement exempt from the registration requirements of the Securities Act of 1933, as amended. ( 3 )These shares of the Issuer's common stock are held of record by OrbiMed Private Investments V, LP ("OPI V"). OrbiMed Capital GP V LLC ("GP V") is the general partner of OPI V, and OrbiMed Advisors is the managing member of GP V. By virtue of such relationships, GP V and OrbiMed Advisors may be deemed to have voting and investment power with respect to the securities held by OPI V noted above and as a result may be deemed to beneficially own such securities for purposes of Rule 13d-3 under the Exchange Act. OrbiMed Advisors exercises this investment and voting power through a management committee comprised of the Reporting Person, Sven H. Borho, and Jonathan T. Silverstein, each of whom disclaims beneficial ownership of the Shares held by OPI V. ( 4 )These shares of the Issuer's common stock are held of record by OrbiMed Israel Partners Limited Partnership ("OIP"). OrbiMed Israel BioFund GP Limited Partnership ("OrbiMed BioFund") is the general partner of OIP, and OrbiMed Israel GP Ltd. ("OrbiMed Israel GP") is the general partner of OrbiMed BioFund. By virtue of such relationships, OrbiMed BioFund and OrbiMed Israel GP may be deemed to have voting and investment power with respect to the shares held directly by OIP noted above and, as a result, may be deemed to beneficially own such securities for purposes of Rule 13d-3 under the Exchange Act. OrbiMed Israel GP exercises this investment and voting power through a management committee comprised of the Reporting Person, Jonathan T. Silverstein, Nissim Darvish, Anat Naschitz, and Erez Chimovits, each of whom disclaims beneficial ownership of the shares held by OIP. ( 5 )These shares of the Issuer's common stock are held of record by OrbiMed Israel Partners II, L.P. ("OIP II"). OrbiMed Israel GP II, L.P. ("OrbiMed Israel GP II") is the general partner of OIP II, and OrbiMed Advisors Israel II Limited ("OrbiMed Israel II") is the general partner of OrbiMed Israel GP II. By virtue of such relationships, OrbiMed Israel GP II and OrbiMed Israel II may be deemed to have voting and investment power with respect to the shares held directly by OIP II noted above and, as a result, may be deemed to beneficially own such securities for purposes of Rule 13d-3 under the Exchange Act. OrbiMed Israel II exercises this investment and voting power through a management committee comprised of the Reporting Person, Jonathan T. Silverstein, Nissim Darvish, Anat Naschitz, and Erez Chimovits, each of whom disclaims beneficial ownership of the shares held by OIP II. ( 6 )Each of the Reporting Person, OrbiMed Advisors, GP V, GP VI, OrbiMed BioFund, OrbiMed Israel GP, OrbiMed Israel GP II and OrbiMed Israel II disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Exchange Act, except to the extent of his or its pecuniary interest therein, if any. This report shall not be deemed an admission that any of the Reporting Person, OrbiMed Advisors, GP V, GP VI, OrbiMed BioFund, OrbiMed Israel GP, OrbiMed Israel GP II or OrbiMed Israel II is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

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