Prime Medicine Stock Jumps More Than 12% After Hours as FDA Clears PM647 for Human Testing

Prime Medicine (NASDAQ: PRME) shares jumped more than 12% in after-hours trading Thursday after the U.S. Food and Drug Administration cleared the company’s Investigational New Drug application for PM647, allowing the experimental gene-editing therapy to move into human testing. 

PM647 is being developed as a one-time in vivo Prime Editing treatment for Alpha-1 Antitrypsin Deficiency, or AATD. The therapy is designed to correct the E342K, or Pi*Z, mutation in the SERPINA1 gene, which is the most common genetic cause of the disorder.

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FDA Clearance Opens Phase 1/2 Trial 

The FDA decision enables Prime Medicine to begin clinical testing of PM647 in the United States. The company said approximately 100,000 people in the U.S. carry the PiZZ genotype targeted by the therapy. 

Prime Medicine plans a global Phase 1/2, single-arm, open-label study evaluating the safety, tolerability and preliminary efficacy of ascending doses of PM647. Participants will receive a one-time intravenous infusion. 

The trial will initially enroll adults with lung-only manifestations of AATD. If tolerability is established in those patients, Prime Medicine plans to add a separate cohort of adults with significant liver disease, including patients who may also have lung manifestations. The company expects initial clinical data in 2027. 

PM647 Extends Prime Medicine’s Liver Pipeline Into the Clinic

PM647 is designed to restore production of functional alpha-1 antitrypsin by correcting the underlying mutation rather than replacing the missing protein. AATD can cause progressive lung damage and liver disease, and Prime Medicine says there is currently no approved curative treatment addressing the genetic cause of both manifestations.

The program uses the same liver-directed lipid nanoparticle delivery system as PM577a, Prime Medicine’s investigational treatment for Wilson disease. PM577a previously received regulatory clearances in the U.S. and New Zealand for a global Phase 1/2 program, giving Prime Medicine two in vivo liver programs moving into clinical development.