Prime Medicine, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934 (Amendment No. )

Check the appropriate box:

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

NOTICE OF 2026 ANNUAL MEETING OF STOCKHOLDERS

To Be Held On June 5, 2026

We are pleased to notify you that we will hold the 2026 annual meeting of our stockholders, or the Annual Meeting, on June 5, 2026, at 2:00 p.m., Eastern Time, in a virtual meeting format, which will be conducted via live webcast. You may attend the Annual Meeting online, vote your shares electronically and submit questions by visitingwww.virtualshareholdermeeting.com/PRME2026.

The Annual Meeting will be held for the following purposes:

1. To elect Michael Kelly and David Schenkein, M.D. as Class I Directors, each to serve until the 2029 annual meeting of our stockholders, and until his respective successor shall have been duly elected and qualified, or until his earlier death, resignation or removal;

2. To ratify the appointment of PricewaterhouseCoopers LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2026; and

3. To transact such other business as may properly come before the Annual Meeting or any continuations, adjournments, and postponements thereof.

Our Board of Directors has established the close of business on April 9, 2026 as the “record date” for the Annual Meeting. This means that you are entitled to notice of, and to vote at, the Annual Meeting or any continuations, adjournments, and postponements thereof if our stock records show that you owned our common stock at that time.

Under the Securities and Exchange Commission rules that allow companies to furnish their proxy materials to stockholders over the Internet under the “notice and access” approach, we have elected to make our proxy materials available to our stockholders over the Internet. As a result, we are mailing to our stockholders a Notice of Internet Availability of Proxy Materials, or the Notice, instead of a paper copy of the accompanying proxy statement for the Annual Meeting and our annual report to our stockholders for the fiscal year ended December 31, 2025, or the 2025 Annual Report. This method allows us to provide our stockholders with the information they need on a more timely basis, while at the same time conserving natural resources and lowering the costs of printing and delivering our proxy materials. On or about April 23, 2026, we will commence sending to our stockholders the Notice, containing instructions on how to access our proxy statement for the Annual Meeting and our 2025 Annual Report online. The Notice also provides instructions on how to vote online or vote by phone and includes instructions on how to receive a paper copy of the proxy materials by mail if desired.

Whether you plan to attend the Annual Meeting or not, it is important that your shares be represented. You may vote over the Internet, via telephone or by mail. You are urged to vote in accordance with the instructions set forth in this proxy statement. We encourage you to vote by proxy so that your shares will be represented and voted at the Annual Meeting, whether or not you can attend. You will need the 16-digit control number included with the Notice, on your proxy card or the instructions that accompany your proxy materials to attend the Annual Meeting virtually via the Internet. Submitting your vote via the Internet or by telephone or proxy card will not affect your right to vote online during the Annual Meeting.

Thank you for your continued support of Prime Medicine, Inc.

By Order of the Board of Directors,

/s/ Allan Reine

Allan Reine

Chief Executive Officer and Director

April 23, 2026

Cambridge, Massachusetts

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