Company: PRME
Filing Date: 2025-05-19
Form Type: DEFA14A
Source: 0001193125-25-122158
Chunk: 1

Company: Prime Medicine, Inc.
Filing Date: 2025-05-19
Form: DEFA14A
Chunk 1
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 pursuant to Rule 14a-12 under the Exchange Act (17 
 CFR 240.14a-12)                                                        |

| ☐ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) |

| ☐ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) |

Securities registered pursuant to Section 12(b) of the Act:

| Title of each class                        |     | Trading   
 Symbol(s) |     | Name of each exchange    
 on which registered      |
| Common stock, par value $0.00001 per share |     | PRME      |     | The Nasdaq Global Market |

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule12b-2of the Securities Exchange Act of 1934 (§250.12b-2of this chapter). Emerging growth company ☒ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

Departure of President, Chief Executive Officer and Principal Executive Officer

On May 19, 2025, Prime Medicine, Inc. (the “Company”) announced that Keith Gottesdiener, M.D. had resigned as President, Chief Executive Officer
and principal executive officer of the Company, and as a member of the Board of Directors of the Company (the “Board”), as well as from all other officer and director positions he held with the Company and any of its subsidiaries, in each
case effective as of the end of day on May 18, 2025 (the “Resignation”). Dr. Gottesdiener’s decision to resign from the Board was not the result of any disagreement with the Company on any matter relating to the operations,
policies or practices of the Company.

In connection with the Resignation, Dr. Gottesdiener and the Company entered into a Separation Agreement (the
“Separation Agreement”), pursuant