Robert Nelsen - 01 Aug 2025 Form 4 Insider Report for Prime Medicine, Inc. (PRME)

Reporting relationship: Director, 10%+ Owner
Issuer ticker: PRME
Reported as of: 01 Aug 2025
Net transaction value: +$9,999,990
SEC form: 4
Accepted by SEC: 01 Aug 2025, 19:19:58 UTC
Prior SEC filing: 09 Jun 2025
Next SEC filing: 05 Jun 2026
Source filing: View source filing
Reporting owner signature: Robert Nelsen /s/ Mark McDonnell, attorney-in-fact

Key filing fact

Robert Nelsen filed Form 4 for Prime Medicine, Inc. (PRME) on 01 Aug 2025.

Key facts

This page summarizes Robert Nelsen's Form 4 filing for Prime Medicine, Inc. (PRME).
1 reported transaction and 0 derivative rows are listed below.
Accepted by SEC: 01 Aug 2025, 19:19.

Change

Previous filing in this sequence was filed on 09 Jun 2025.
Current net transaction value: +$9,999,990.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001219042 Primary reporting owner

NELSEN ROBERT

Relationship: Director, 10%+ Owner
Address: 8755 W. HIGGINS ROAD, SUITE 1025, CHICAGO
Signature: Robert Nelsen /s/ Mark McDonnell, attorney-in-fact
Signature date: 01 Aug 2025

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

PRME transaction

Common Stock

Purchase

Transaction value: $9,999,990
Shares: +3,030,300
Change %: +95%
Price: $3.30
Shares after: 6,230,300
Date: 01 Aug 2025
Ownership: By ARCH Venture Fund XII, L.P.
Footnotes: F5, F6

PRME holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 6,128,297
Date: 01 Aug 2025
Ownership: By ARCH Venture Fund X, L.P.
Footnotes: F1, F3, F4

PRME holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 6,128,297
Date: 01 Aug 2025
Ownership: By ARCH Venture Fund X Overage, L.P.
Footnotes: F2, F3, F4

PRME holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 16,080
Date: 01 Aug 2025
Ownership: See Footnote
Footnotes: F7

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 7 footnotes

Footnote F1

Represents shares held directly by ARCH Venture Fund X, L.P. ("ARCH X"). ARCH Venture Partners X, L.P. ("AVP X LP") is the sole general partner of ARCH X.

Footnote F2

Represents shares held directly by ARCH Venture Fund X Overage, L.P. ("ARCH X Overage"). ARCH Venture Partners X Overage, L.P. ("AVP X Overage LP") is the sole general partner of ARCH X Overage.

Footnote F3

ARCH Venture Partners X, LLC ("AVP X LLC") is the sole general partner of each of AVP X LP and AVP X Overage LP. In addition to the Reporting Person, Keith Crandell, Kristina Burow and Steve Gillis are also members of the investment committee of AVP X LLC (the "AVP X Investment Committee Members"). AVP X LP and AVP X Overage LP may be deemed to beneficially own the shares held by ARCH X and ARCH X Overage, respectively, AVP X LLC may be deemed to beneficially own the shares held by ARCH X and ARCH X Overage, and each of the AVP X Investment Committee Members may be deemed to share the power to direct the disposition and vote of the shares held by ARCH X and ARCH X Overage. AVP X LP, AVP X Overage LP, AVP X LLC, and the other AVP X Investment Committee Members have filed a separate Form 4 and disclaim beneficial ownership except to the extent of any pecuniary interest therein.

Footnote F4

The Reporting Person is also an AVP X Investment Committee Member and may be deemed to share the power to direct the disposition and vote of own the shares held by ARCH X and ARCH X Overage. The Reporting Person disclaims beneficial ownership of such shares except to the extent of any pecuniary interest therein, and this report shall not be deemed an admission that such shares are beneficially owned by him for Section 16 or any other purpose.

Footnote F5

Represents shares held directly by ARCH Venture Fund XII, L.P. ("ARCH XII"). ARCH Venture Partners XII, L.P. ("AVP XII LP") is the general partner of ARCH XII. ARCH Venture Partners XII, LLC (AVP XII LLC) is the general partner of AVP XII LP. In addition to the Reporting Person, Keith Crandell, Kristina Burow and Steven Gillis are also members of the investment committee of AVP XII LLC (the "AVP XII LLC Investment Committee Members"). Each of AVP XII LP and AVP XII LLC may be deemed to beneficially own the shares held by ARCH XII, and each of the AVP XII LLC Investment Committee Members may be deemed to share the power to direct the disposition and vote of the shares held by ARCH XII. Each of AVP XII LP, AVP XII LLC and the other AVP XII LLC Investment Committee Members have filed a separate Form 4 and disclaim beneficial ownership except to the extent of their pecuniary interest therein, if any.

Footnote F6

The Reporting Person is also an AVP XII Investment Committee Member and may be deemed to to share the power to direct the disposition and vote of the shares held by ARCH XII. The Reporting Person disclaims beneficial ownership of such shares except to the extent of any pecuniary interest therein, and this report shall not be deemed an admission that such shares are beneficially owned by him for Section 16 or any other purpose.

Footnote F7

Shares held by a trust for the benefit of family members of the Reporting Person.