Prime Medicine, Inc. Insider Trading Activity

Insider Trade Summary

Net Buyer: 1,500,000 shares

Net Buy 1 txn

Insider GV 2021 GP, L.L.C., GV 2021 GP, L.P., GV 2021, L.P., Alphabet Inc.

Role 10% Owner | 10% Owner | 10% Owner | 10% Owner

Bought 1,500,000 shs ($4.95M)

Type	Security	Shares	Price	Value
Purchase	Common Stock	1,500,000	$3.30	$4.95M

Holdings After Transaction: Common Stock — 3,262,440 shares (Indirect, By GV 2021, L.P.)

Footnotes (2)

1. F1. Represents shares purchased in connection with an underwritten public offering of the Issuer's Common Stock that closed on August 1, 2025.
2. F2. The securities reported in this row are directly beneficially owned by GV 2021, L.P. (the "2021 Partnership"). The general partner of the 2021 Partnership is GV 2021 GP, L.P. (the "2021 GP"). The general partner of the 2021 GP is GV 2021 GP, L.L.C. ("GV 2021 LLC"). The sole member of GV 2021 LLC is Alphabet Holdings LLC ("Alphabet Holdings"). The sole member of Alphabet Holdings is XXVI Holdings Inc. ("XXVI"). The controlling stockholder of XXVI is Alphabet Inc. Each of the 2021 GP, GV 2021 LLC, Alphabet Holdings, XXVI, and Alphabet Inc. may be deemed to indirectly beneficially own (as the term is defined in Rule 13d-3 of the Securities Exchange Act of 1934, as amended) the securities directly beneficially owned by the 2021 Partnership. Each of the aforementioned parties disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.

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Accepted by SEC EDGAR 08/05/2025 - 04:07 PM EDT Learn about SEC filing dates

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^*

GV 2021 GP, L.L.C.

(Last) (First) (Middle)

1600 AMPHITHEATRE PARKWAY

(Street)

MOUNTAIN VIEW CA 94043

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Prime Medicine, Inc. [ PRME ]

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)
08/01/2025

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	08/01/2025		P(1)		1,500,000	A	$3.3	3,262,440	I	By GV 2021, L.P.(2)

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^*

GV 2021 GP, L.L.C.

(Last) (First) (Middle)

1600 AMPHITHEATRE PARKWAY

(Street)

MOUNTAIN VIEW CA 94043

(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^*

GV 2021 GP, L.P.

(Last) (First) (Middle)

1600 AMPHITHEATRE PARKWAY

(Street)

MOUNTAIN VIEW CA 94043

(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^*

GV 2021, L.P.

(Last) (First) (Middle)

1600 AMPHITHEATRE PARKWAY

(Street)

MOUNTAIN VIEW CA 94043

(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^*

Alphabet Inc.

(Last) (First) (Middle)

1600 AMPHITHEATRE PARKWAY

(Street)

MOUNTAIN VIEW CA 94043

(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. Represents shares purchased in connection with an underwritten public offering of the Issuer's Common Stock that closed on August 1, 2025.

2. The securities reported in this row are directly beneficially owned by GV 2021, L.P. (the "2021 Partnership"). The general partner of the 2021 Partnership is GV 2021 GP, L.P. (the "2021 GP"). The general partner of the 2021 GP is GV 2021 GP, L.L.C. ("GV 2021 LLC"). The sole member of GV 2021 LLC is Alphabet Holdings LLC ("Alphabet Holdings"). The sole member of Alphabet Holdings is XXVI Holdings Inc. ("XXVI"). The controlling stockholder of XXVI is Alphabet Inc. Each of the 2021 GP, GV 2021 LLC, Alphabet Holdings, XXVI, and Alphabet Inc. may be deemed to indirectly beneficially own (as the term is defined in Rule 13d-3 of the Securities Exchange Act of 1934, as amended) the securities directly beneficially owned by the 2021 Partnership. Each of the aforementioned parties disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.

	/s/ Inga Goldbard, General Counsel of GV 2021 GP, L.L.C.	08/05/2025
	/s/ Inga Goldbard, General Counsel of GV 2021 GP, L.P.	08/05/2025
	/s/ Inga Goldbard, General Counsel of GV 2021, L.P.	08/05/2025
	/s/ Kathryn W. Hall, Assistant Secretary of Alphabet Inc.	08/05/2025
	** 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.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.