Company: PRME
Filing Date: 2025-05-19
Form Type: DEFA14A
Source: 0001193125-25-122158
Chunk: 0

Company: Prime Medicine, Inc.
Filing Date: 2025-05-19
Form: DEFA14A
Chunk 0
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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. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box:

| ☐ | Preliminary Proxy Statement |

| ☐ | Confidential, for Use of the Commission Only (as permitted by Rule 
 14a-6(e)(2))                                                       |

| ☐ | Definitive Proxy Statement |

| ☒ | Definitive Additional Materials |

| ☐ | Soliciting Material under §240.14a-12 |

PRIME MEDICINE, INC. (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):

| ☒ | No fee required. |

| ☐ | Fee paid previously with preliminary materials. |

| ☐ | Fee computed on table below in exhibit required by Item 25(b) Exchange Act Rules 
 14a-6(i)(14) and 0-11.                                                           |

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 May 16, 2025 Date of Report (Date of earliest event reported) Prime Medicine, Inc. (Exact name of registrant as specified in its charter)

| Delaware                                 
 (State or other jurisdiction of          
 incorporation)                           |     | 001-41536        
 (Commission File 
 Number)          |     |          84-3097762 
    (I.R.S. Employer 
 Identification No.) |
| 60 First Street                          
 Cambridge, MA                            |     |                  |     |               02141 |
| (Address of principal executive offices) |     |                  |     |           -Zip Code |

(617) 465-0013 (Registrant’s telephone number, including area code) Check the appropriate box below if the Form 8-Kfiling is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

| ☐ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) |

| ☐ | Soliciting material