Company: PRME
Filing Date: 2025-07-02
Form Type: PRE 14A
Source: 0001193125-25-155000
Chunk: 5

Company: Prime Medicine, Inc.
Filing Date: 2025-07-02
Form: PRE 14A
Chunk 5
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 of stockholders entitled to vote at the Special Meeting will be available for inspection at the headquarters of the Company, 60 First Street, Cambridge, MA 02141, during ordinary business hours, by any stockholder for any purpose germane to the Special Meeting, for a period of ten (10) days prior to the Special Meeting. Voting Shares That You Hold in Your Name If you are a stockholder of record and your shares are registered directly in your name, you may vote:

| • |     | BY PHONE – Use a touch-tone phone by calling 1-800-690-6903 (toll-free from the U.S., U.S. territories and Canada) to transmit your voting instructions up until 11:59 p.m., Eastern Time, on July 31, 2025. 
 Have your proxy card in hand when you access the phone number. Follow the steps outlined on the phone line.                                                                                                  |

| • |     | VOTE DURING THE VIRTUAL MEETING – See “Attending the Special Meeting,” below. |

If the Special Meeting is adjourned or postponed, the deadlines above may be extended. 2

Virtual Meeting The Special Meeting will be a virtual meeting, which will be conducted via live webcast. To participate in the Special Meeting virtually via the Internet, please visit www.virtualshareholdermeeting.com/PRME2025SM. You will need the 16-digitcontrol number included on your proxy card or the instructions that accompanied your proxy materials. If you are a beneficial owner of shares held in “street name” by your bank, brokerage firm or other nominee, you should have received a voting instruction form provided by your bank, brokerage firm or other nominee rather than from us. If you do not have your 16-digitcontrol number and attend the meeting online, you will be able to listen to the meeting only — you will not be able to vote or submit questions during the meeting. Attending the Special Meeting The Special Meeting will be held entirely online at www.virtualshareholdermeeting.com/PRME2025SM. A summary of the information you need to attend the Special Meeting online is provided below:

| • |     | Instructions on how to attend and participate via the Internet, including how to demonstrate proof of common 
 stock ownership, are posted at www.proxyvote.com.                                                            |

| • |     | Please have your 16-digit control number to enter the Special Meeting. |

| • |     | Stockholders may submit questions while attending the Special Meeting via