PM577a

October 5, 2026: Prime Medicine (NASDAQ: PRME) announced the first patient was dosed in a global Phase 1/2 first-in-human trial of PM577a, an in vivo prime editing therapy for Wilson disease in patients with at least one ATP7B p.H1069Q allele. The open-label dose-escalation study will assess safety, tolerability, and preliminary efficacy in adults and adolescents; it will start in clinically stable adults on standard-of-care therapy. Planned efficacy measures include copper efflux by 64Cu PET, serum ceruloplasmin, non-ceruloplasmin-bound copper, and 24-hour urinary copper excretion, and the trial will also evaluate discontinuation of baseline standard-of-care therapies. Trial ID: NCT07748403.

The company also said the FDA granted Rare Pediatric Disease designation to PM577 for Wilson disease.

PM577a is described as a one-time intravenous lipid nanoparticle-formulated therapy targeting the H1069Q mutation, the most prevalent Wilson disease-causing allele in North America and Europe. Initial clinical data are expected in 2027. Prime Medicine also noted a follow-on preclinical candidate targeting the ATP7B R778L mutation, common in East Asian populations.