Prime Medicine Announces The New England Journal of Medicine Publication of PM359 Clinical Data for the Treatment of Chronic Granulomatous Disease

CAMBRIDGE, Mass., Dec. 07, 2025 (GLOBE NEWSWIRE) -- Prime Medicine, Inc. (Nasdaq: PRME), a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies, today announced the publication of Phase 1/2 clinical data with PM359, the Company’s investigational autologous hematopoietic stem cell product for p47^phox chronic granulomatous disease (CGD) in the New England Journal of Medicine (NEJM). The data will also be presented in a poster session at the 67^th American Society of Hematology (ASH) Annual Meeting, December 6-9, 2025 in Orlando, Florida.

The publication, titled “Prime Editing for p47-phox Chronic Granulomatous Disease,” reports initial data for two patients treated in the Phase 1/2 trial of PM359, which was designed to assess safety, biological activity and preliminary efficacy in adult and pediatric study participants. Both patients experienced rapid neutrophil and platelet engraftment, as well as durable restoration of NADPH oxidase activity and early clinical benefit, without any safety concerns. Together, these results provide the first-in-human demonstration of the safety and efficacy of Prime Editing, and support the potential for PM359 as a precise therapeutic strategy for CGD:

• Both patients enrolled in the study had a history of prior CGD-defining complications, including CGD-associated colitis (CAC), and skin and soft tissue infections, and both were maintained on long-term prophylactic therapy.
• Both patients experienced rapid neutrophil engraftment, achieving 69% and 83% dihydrorhodamine-positive (DHR+) neutrophils by Day 30, respectively, far in excess of the 20% projected minimum threshold for clinical benefit. DHR activity remained stable over time in both patients, suggesting that gene correction occurred in the long-term repopulating hematopoietic stem cells (HSCs) of the bone marrow.
• Both patients remain free of new CGD-related complications or significant intercurrent illnesses post-infusion; additionally, Patient 1 stopped his mesalamine treatment and has not experienced a flare of CAC, and Patient 2’s levels of fecal calprotectin have decreased substantially, and his chronic CAC symptoms have abated.
• No clinically significant adverse events attributable to PM359 occurred in either patient, and all observed toxicities were consistent with busulfan-based conditioning.

“Publication of these first-in-human data highlights Prime Editing’s promise as a next-generation therapeutic platform, which is capable of delivering meaningful benefits to patients and which can be manufactured and delivered at clinical scale,” said Mohammed Asmal, M.D., Ph.D., Chief Medical Officer of Prime Medicine. “Beyond demonstrating early clinical efficacy, these results offer important insights into Prime Editing’s safety profile and potential advantages over other gene editing technologies. As described in the NEJM publication, we observed high recovery rates of viable corrected cells after a single mobilization cycle, as well as the rapid reconstitution of the hematopoietic system after infusion. Both support our belief that the mechanism of Prime Editing, which does not induce double-strand breaks, may be better tolerated by HSCs and other cell types – and therefore safer for patients – than other approaches.”