PM359 moves toward IND submission, pushing prime editing closer to human trials

Prime Medicine said on March 3 that PM359, its prime-edited cell therapy for chronic granulomatous disease, is back on a regulatory path after new talks with the Food and Drug Administration. (investors.primemedicine.com) (precisionmedicineonline.com) Prime editing is a gene-editing method meant to rewrite a misspelled DNA sequence rather than cut both strands and hope the cell repairs it correctly. PM359 uses that approach outside the body on a patient’s own blood-forming stem cells, then infuses the edited cells back after conditioning. (sciencedirect.com) (clinicaltrials.gov) The disease target is p47phox chronic granulomatous disease, a rare immune disorder caused here by mutations in the NCF1 gene. ClinicalTrials.gov says about 20% to 25% of people with chronic granulomatous disease carry the delGT mutation in both copies of NCF1, the defect PM359 is built to correct. (clinicaltrials.gov) PM359 is not just nearing human testing; it already cleared an investigational new drug application on April 29, 2024, and entered a first-in-human Phase 1/2 study in the United States. Prime called that clearance the first open IND for a prime-editing product candidate. (investors.primemedicine.com) The company then reported its first human readout on May 19, 2025. Prime said one patient reached 58% DHR positivity by day 15 and 66% by day 30 after a single infusion, with rapid neutrophil and platelet engraftment and no serious adverse events tied to PM359. (biospace.com) That result mattered because Prime had pulled back. In May 2025, the company said it would look for ways to continue PM359 development outside the company as it cut spending and shifted attention to liver programs. (biospace.com) (precisionmedicineonline.com) Now Prime says the opposite direction is possible. In its March 3, 2026 business update, the company said recent conversations with the FDA suggest data from the first two treated patients may support accelerated approval, and it plans to submit a biologics license application after final alignment. (investors.primemedicine.com) (precisionmedicineonline.com) The same update put dates on Prime’s next in vivo programs. PM577 for Wilson disease is on track for an investigational new drug application or clinical trial application in the first half of 2026, and PM647 for alpha-1 antitrypsin deficiency is targeted for mid-2026, with first clinical data for both expected in 2027. (investors.primemedicine.com) (sec.gov) ClinicalTrials.gov still lists the PM359 study as “enrolling by invitation,” with the latest update posted April 6, 2026. The trial starts in adults 18 and older before moving to adolescents and children if early safety and activity hold up. (clinicaltrials.gov) Prime reported $191 million in cash, cash equivalents, investments and restricted cash at year-end 2025, which it said funds operations into 2027. For a field that has spent years in preclinical work, PM359 is now being framed less as a technology demo and more as a possible registration test case. (investors.primemedicine.com)