[Form 4] Adicet Bio, Inc. Insider Trading Activity

Rhea-AI Filing Summary

OrbiMed-related entities reported purchases of Adicet Bio (ACET) common stock on 10/08/2025. The filings show two registered direct offering purchases: 1,500,000 shares at $1 and 3,500,000 shares at $1, increasing combined holdings across affiliated OrbiMed funds and GP vehicles to 9,026,359 and 4,490,254 shares in specific accounts, with additional holdings noted across other funds. The report lists multiple OrbiMed entities and explains their record ownership and GP relationships, while each entity disclaims direct beneficial ownership except to the extent of pecuniary interest. The Form 4s are signed by Carl L. Gordon on 10/10/2025.

Positive

• Large institutional purchase of 5,000,000 shares at $1 indicates material capital commitment
• Transparent disclosure of record holders, GP relationships, and customary disclaimers clarifies voting/investment structure

Negative

• Layered ownership structure via multiple funds makes direct beneficial ownership and control less immediately clear
• No forward intent disclosed beyond the purchases, so investor implications are uncertain

Insights

Institutional Shareholder Analyst

OrbiMed significantly increased position via a registered direct offering totaling 5,000,000 shares at $1.

Multiple affiliated OrbiMed funds purchased a combined 5,000,000 shares on 10/08/2025, which materially raises their reported holdings in different record accounts to the single-digit millions of shares shown. The ownership structure is layered through general partners and funds, and the filing provides the standard disclaimers that voting and investment power may be exercised through committees while individuals disclaim direct beneficial ownership.

The primary risk for investors is limited: these are purchases disclosed under Section 16 and do not by themselves change company operations. Monitor any subsequent Form 13D/G filings or additional Form 4 activity within the next 30 to 90 days for evidence of further accumulation or a coordinated ownership intent.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

ORBIMED ADVISORS LLC

(Last) (First) (Middle)

601 LEXINGTON AVENUE

54TH FLOOR

(Street)

NEW YORK NY 10022

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Adicet Bio, Inc. [ ACET ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
10/08/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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								1,027,885	I	See footnotes(2)(7)
Common Stock								646,657	I	See footnotes(3)(7)
Common Stock	10/08/2025		P		1,500,000(1)	A	$1	9,026,359	I	See footnotes(4)(7)
Common Stock	10/08/2025		P		3,500,000(1)	A	$1	4,490,254	I	See footnotes(5)(7)
Common Stock								1,255,985	I	See footnotes(6)(7)

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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: 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

1. Name and Address of Reporting Person^*

ORBIMED ADVISORS LLC

(Last) (First) (Middle)

601 LEXINGTON AVENUE

54TH FLOOR

(Street)

NEW YORK NY 10022

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

OrbiMed Capital GP V LLC

(Last) (First) (Middle)

601 LEXINGTON AVENUE

54TH FLOOR

(Street)

NEW YORK NY 10022

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

OrbiMed Capital GP VI LLC

(Last) (First) (Middle)

601 LEXINGTON AVENUE, 54TH FLOOR

(Street)

NEW YORK NY 10022

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

OrbiMed Genesis GP LLC

(Last) (First) (Middle)

601 LEXINGTON AVENUE, 54TH FLOOR

(Street)

NEW YORK NY 10022

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

OrbiMed Advisors Israel II Ltd

(Last) (First) (Middle)

5 HAHOSHLIM STREET, BUILDING B

1ST FLOOR

(Street)

HERZLIYA PITUACH L3 46686

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

OrbiMed Israel GP II, L.P.

(Last) (First) (Middle)

5 HAHOSHLIM STREET, BUILDING B

1ST FLOOR

(Street)

HERZLIYA PITUACH L3 46686

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

OrbiMed Israel GP Ltd.

(Last) (First) (Middle)

5 HAHOSHLIM STREET, BUILDING B

1ST FLOOR

(Street)

HERZLIYA PITUACH L3 46686

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

OrbiMed Israel BioFund GP Limited Partnership

(Last) (First) (Middle)

5 HAHOSHLIM STREET, BUILDING B

1ST FLOOR

(Street)

HERZLIYA PITUACH L3 46686

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. These securities were purchased in an underwritten registered direct offering.

2. These securities 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 over the shares of common stock held by OIP and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed Israel GP exercises this investment and voting power through an investment committee comprised of Carl L. Gordon and Erez Chimovits, each of whom disclaims beneficial ownership over the shares of common stock held by OIP.

3. These securities 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 over the shares of common stock held by OIP II and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed Israel II exercises this investment and voting power through an investment committee comprised of Carl L. Gordon, David Bonita, and Erez Chimovits, each of whom disclaims beneficial ownership over the shares of common stock held by OIP II.

4. These securities 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 LLC ("OrbiMed Advisors"), a registered investment adviser under the Investment Advisors Act of 1940, as amended, 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 over the shares of common stock held by OPI V and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed 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 over the shares of common stock held by OPI V.

5. These securities 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 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 over the shares of common stock held by OPI VI and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed 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 over the shares of common stock held by OPI VI.

6. These securities are held of record by OrbiMed Genesis Master Fund, L.P. ("Genesis"). OrbiMed Genesis GP LLC ("Genesis GP") is the general partner of Genesis, and OrbiMed Advisors is the managing member of Genesis. By virtue of such relationships, Genesis GP and OrbiMed Advisors may be deemed to have voting and investment power over the shares of common stock held by Genesis and, as a result, may be deemed to have beneficial ownership over such shares of common stock. OrbiMed 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 over the shares of common stock held by Genesis.

7. Each of OrbiMed Advisors, OrbiMed BioFund, OrbiMed Israel GP, OrbiMed Israel GP II, OrbiMed Israel II, GP V, GP VI, and Genesis GP disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (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 such person or entity is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

	/s/ Carl L. Gordon, Member of OrbiMed Advisors LLC	10/10/2025
	/s/ Carl L. Gordon, Member of OrbiMed Capital GP V LLC	10/10/2025
	/s/ Carl L. Gordon, Member of OrbiMed Capital GP VI LLC	10/10/2025
	/s/ Carl L. Gordon, Member of OrbiMed Genesis GP LLC	10/10/2025
	/s/ Carl L. Gordon, Director of OrbiMed Israel GP Ltd.	10/10/2025
	/s/ Carl L. Gordon, Director of OrbiMed Advisors Israel II Ltd.	10/10/2025
	/s/ Carl L. Gordon, Director of OrbiMed Israel GP II, L.P.	10/10/2025
	/s/ Carl L. Gordon, Director of OrbiMed Israel BioFund GP Limited Partnership	10/10/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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FAQ

What did OrbiMed purchase in the ACET Form 4 filings?

Affiliated OrbiMed funds purchased a total of 5,000,000 common shares on 10/08/2025 via a registered direct offering at $1 per share.

How many ACET shares do OrbiMed entities report owning after the transactions?

The filings show holdings including 9,026,359 and 4,490,254 shares in specific accounts, plus other fund-level holdings listed in the Form 4s.

Who signed the Form 4 filings for ACET?

The filings are signed by Carl L. Gordon in various capacities for the OrbiMed reporting entities on 10/10/2025.

Were these purchases part of a rule 10b5-1 plan or similar?

The filings indicate the purchases were made in an underwritten registered direct offering; no 10b5-1 plan is asserted in the disclosed explanation.

Do the filings show OrbiMed intends to control Adicet Bio (ACET)?

No controlling intent is disclosed; the filings include standard disclaimers that the entities may be deemed to have voting or investment power but disclaim direct beneficial ownership except for pecuniary interest.