Company: PRME
Filing Date: 2025-05-19
Form Type: DEFA14A
Source: 0001193125-25-122158
Chunk: 7

Company: Prime Medicine, Inc.
Filing Date: 2025-05-19
Form: DEFA14A
Chunk 7
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 of the Board, as Executive Chair of the Board, in addition to his
service as a director, effective as of May 19, 2025.

Pipeline Prioritization

On May 19, 2025, the Company announced a strategic restructuring, including the deprioritization of its Chronic Granulomatous Disease (“CGD”)
programs, as well as a cost and workforce reduction to focus on its liver franchise and programs funded through external partnerships. The Company will focus its internal efforts on the development of in vivoprograms for the treatment of
Wilson’s Disease and Alpha-1 Antitrypsin Deficiency (“AATD”), two of the largest genetic liver diseases. The Company expects to file an investigational new drug (“IND”) and/or clinical
trial application (“CTA”) for its Wilson’s Disease program in the first half of 2026 and for its AATD program in mid-2026; initial clinical data from both programs are expected in 2027.

The Company will also continue its in vivoCystic Fibrosis program with support from the Cystic Fibrosis Foundation, and its efforts to develop Prime
Edited CAR-T products for hematology, immunology and oncology in partnership with Bristol Myers Squibb. The Company is exploring options for the continued clinical development of PM359 external to the Company
and ceasing further efforts in X-linked CGD. The Company believes PM359 has the potential to transform the care of p47phox CGD and is committed to working with urgency to identify an appropriate partner to
help ensure this important therapy is delivered to patients. In addition, the Company will continue to pursue additional business development opportunities to accelerate innovation, ensure the broadest application of Prime Editing, and further
bolster its financial resources.

CGD Data Update

On May 19, 2025, the Company announced positive initial data from the first patient dosed in its ongoing Phase 1/2 clinical study of PM359 in CGD.
Preliminary results from the first patient demonstrated that PM359 was well-tolerated, showed rapid engraftment and restored NADPH oxidase activity to well above the threshold for clinical benefit, as measured by the dihydrorhodamine
(“DHR”) assay. PM359 is being evaluated in a Phase 1/2, multinational, first-in-human trial designed to assess safety, biological activity and preliminary
efficacy in adult and pediatric study participants. Initial safety and efficacy data