Prime Medicine Doses First In Vivo Prime Editing Patient

The Tip Desk · November 13, 2026 · 3 min read

The company raised $143.7 million gross in November, lifting pro-forma cash to about $209.5 million and extending the runway through 2027.

Prime Medicine, Inc. (PRME), a biotechnology company developing one-time curative genetic therapies, dosed the first patient in October 2026 in a global Phase 1/2 trial of PM577a for Wilson disease, the first clinical study of an in vivo Prime Editing therapy from the company.

The trial (NCT07748403) is an open-label, first-in-human study of ascending doses of PM577a in adults and adolescents with Wilson disease who carry at least one p.H1069Q allele in the ATP7B gene. It is initially enrolling adults who are clinically stable on standard-of-care therapy. Initial clinical data are expected in 2027.

The dosing followed June and July 2026 clearances of an Investigational New Drug application in the United States and a Clinical Trial Application in New Zealand, which had established the global program with startup activities underway. In October the FDA also granted Rare Pediatric Disease designation to PM577 for Wilson disease. PM577a targets the ATP7B H1069Q mutation, which the company said is the most prevalent Wilson disease-causing allele in North America and Europe. A follow-on candidate, PM577b, targeting the R778L mutation, is in preclinical development.

In September 2026 the FDA cleared the company’s IND for PM647, an in vivo Prime Editor designed to correct the E342K (Pi*Z) mutation in the SERPINA1 gene, the most common cause of Alpha-1 Antitrypsin Deficiency. The clearance enabled PM647 to proceed to a planned global, single-arm, open-label Phase 1/2 study, initially in the United States, where the company said approximately 100,000 people carry the PiZZ genotype. The study will initially enroll adults with lung-only manifestations and, upon demonstration of tolerability, expand to a cohort with significant liver disease. Initial clinical data are also expected in 2027. The IND clearance followed a July 2026 arbitration resolution with Beam Therapeutics in which a tribunal declared PM647 within Prime Medicine’s field under the parties’ 2019 collaboration.

Chief Executive Officer Allan Reine said the company views Wilson disease and AATD as the foundation of a liver franchise built on a shared technology platform. He said the two wholly owned liver programs had moved into, or been cleared for, clinical development in months.

Prime Medicine reiterated a planned Biologics License Application for PM359 in chronic granulomatous disease in the first half of 2027, matching the prior-quarter target after Regenerative Medicine Advanced Therapy designation and continued FDA engagement. PM359 also holds Fast Track, Orphan Drug and Rare Pediatric Disease designations.

For the three months ended September 30, 2026, net loss was $39.0 million, or $0.22 a share, compared with $50.6 million, or $0.32 a share, a year earlier. Total revenue was $4.2 million, versus $1.2 million. Research and development expenses were $34.1 million, down from $44.0 million; the company said third-quarter 2025 R&D was higher due to restricted stock unit issuance and that lab equipment repair and maintenance facility costs decreased in the latest quarter. General and administrative expenses were $10.0 million, versus $11.2 million, primarily from lower corporate legal fees. Loss from operations was $39.9 million, and total operating expenses were $44.1 million.

Cash, cash equivalents, investments and restricted cash were $74.8 million as of September 30, 2026, versus $191.4 million as of December 31, 2025. In November 2026 the company completed an underwritten public offering, including full exercise of the underwriters’ option, raising $143.7 million gross and about $134.7 million net. Pro-forma cash, cash equivalents, investments and restricted cash were approximately $209.5 million. The company said that, together with those net proceeds, cash on hand is expected to fund operating expenses and capital expenditure through 2027.

The company is also advancing an in vivo cystic fibrosis program with support from the Cystic Fibrosis Foundation and Prime Edited ex vivo CAR-T products in partnership with Bristol Myers Squibb.