Company: PRME
Filing Date: 2025-07-14
Form Type: DEF 14A
Source: 0001193125-25-158716
Chunk: 5

Company: Prime Medicine, Inc.
Filing Date: 2025-07-14
Form: DEF 14A
Chunk 5
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 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 the Internet. For instructions on 
 how to do so, see below.