Despite hitting a clinical “milestone,” Prime Medicine is shelving its sole clinical-stage genetic medicine.
The Cambridge, Massachusetts-based biotech is also laying off staffers and CEO Keith Gottesdiener, M.D., is resigning, according to Securities and Exchange Commission (SEC) documents filed May 19. The biotech’s board appointed Prime Chief Financial Officer Allan Reine, M.D., to helm the company as he continues with his current responsibilities.
The workforce reduction will impact 25% of staffers, Reine told Fierce Biotech in an emailed statement.
In a separate May 19 release, Prime said its lead candidate—dubbed PM359 and made up of autologous hematopoietic stem cells modified ex vivo using “prime editors”—was well tolerated in the first patient dosed in a phase 1/2 trial for chronic granulomatous disease. The rare inherited disease causes recurrent and debilitating infections.
No serious adverse events related to one dose of the investigational medicine were reported in the preliminary results. The therapy was tied to restoration of NADPH oxidase activity in 66% of neutrophils by Day 30, "well above the threshold for clinical benefit," Prime explained in the release.
“We created prime editing five and a half years ago as a versatile, precise genome editing technology that in principle could correct almost all mutations known to cause genetic diseases,” David Liu, Ph.D., co-founder of Prime and director of the Merkin Institute of Transformative Technologies in Healthcare at the Broad Institute of MIT and Harvard, said in the release. “Today’s data represent a milestone in medicine, establishing that prime editing in a patient's cells can correct a pathogenic mutation and can change the course of a life-limiting disease.”
Despite this, the biotech is ending further internal development of the asset.
Prime is looking for external options that could yield further clinical development of PM359, which has snagged rare pediatric drug and orphan drug tags from the FDA.
The biotech will instead turn its focus toward its preclinical in vivo liver franchise, with the biotech anticipating an IND submission in program in the first half of 2026.
"While a number of the roles impacted in today’s announcement were related to PM359, it is important to underscore that other parts of the business were also affected in an effort to redefine Prime Medicine’s operating model," Reine told Fierce. "These included roles in R&D and CMC as well as in G&A and other parts of our business. In totality, our objective is to operate as a lean, nimble biotech driving towards key data readouts in Wilson’s Disease and Alpha-1 Antitrypsin Deficiency."
Since market open on Monday, Prime’s stock has dropped 19% to $1.28 per share.
The biotech will continue work on developing CAR-T products for hematology, immunology and oncology with Bristol Myers Squibb. The Big Pharma paid $110 million in cash last fall to partner up with Prime, offering the biotech the chance to make up to $3.5 billion in milestones off the deal.
Around the same time the pact was inked, the biotech “strategically focused” its portfolio and was looking to partner off assets that were deprioritized at the time, according to the SEC filings.
The biotech unveiled in 2021 with a hefty $315 million. By the end of last year, the biotech employed 214 full-time staffers, according to SEC documents. At that time, the biotech had $190 million on hand, a cash runway expected to fund operations into the first half of 2026.
Amid a long-lasting industry bear market, gene therapy has been hit especially hard, with numerous large players moving away from the area as of late.
Editor's note: This story was updated at 3:50 p.m. ET on May 19 to include comment from Prime.