CAMBRIDGE, Mass., June 18, 2026
Prime Medicine, Inc. announced that New Zealand’s Medicines and Medical Devices Safety Authority (Medsafe) has cleared the Clinical Trial Application (CTA) for PM577a, an investigational in vivo Prime Editing therapy for Wilson disease. The clearance marks the first-ever clinical authorization for an in vivo Prime Editing therapy from Prime Medicine and enables the initiation of a global Phase 1/2 clinical trial expected to begin in the second half of 2026. Initial clinical data are anticipated in 2027, representing a significant milestone for the company’s gene-editing platform aimed at delivering one-time curative genetic therapies.
First Clinical Authorization Advances Prime Editing Into Human Trials
PM577a is designed to precisely correct the H1069Q mutation in the ATP7B gene, the most common disease-causing mutation responsible for Wilson disease in North America and Europe, accounting for approximately 30–50% of disease-associated variants. The investigational therapy uses lipid nanoparticle (LNP) delivery to transport Prime Editing components directly to liver cells through a single intravenous infusion, with the goal of correcting the underlying genetic defect rather than managing symptoms. Prime Medicine also plans to expand the platform with additional candidates, including a preclinical program targeting the R778L mutation, the most prevalent ATP7B mutation among East Asian populations, highlighting the modular potential of its gene-editing technology.
Global Phase 1/2 Study to Evaluate Safety and Biological Activity
The open-label, first-in-human Phase 1/2 clinical trial will evaluate the safety, tolerability, biological activity, and efficacy of ascending doses of PM577a in adults and adolescents with Wilson disease. The study will initially enroll clinically stable adult patients receiving standard-of-care treatment before expanding to broader patient populations. Key biological and efficacy endpoints include copper transport measured by 64Cu PET imaging, serum ceruloplasmin, non-ceruloplasmin-bound copper, 24-hour urinary copper excretion, and liver copper levels determined through biopsy. The incorporation of 64Cu PET imaging provides a novel, non-invasive method for assessing restoration of ATP7B function and will play a central role in evaluating proof-of-concept during the study.
Prime Editing Targets the Root Cause of Wilson Disease
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Wilson disease is a rare inherited disorder caused by mutations in the ATP7B gene, resulting in impaired copper metabolism and progressive accumulation of copper in the liver, brain, kidneys, and other organs. Current therapies, including copper chelators and zinc salts, require lifelong treatment, are associated with adherence challenges and adverse effects, while liver transplantation remains the only curative option. Prime Medicine believes PM577a has the potential to become a one-time genomic therapy that directly corrects the disease-causing mutation, offering a transformative treatment approach for patients with Wilson disease. The successful CTA clearance represents an important regulatory milestone as the company advances its broader pipeline of Prime Editing therapies targeting liver, lung, immunology, and oncology indications.
Source: Prime Medicine press release
