Prime to seek FDA approval for gene-editing treatment using two-patient trial

Prime Medicine will seek accelerated FDA approval of its ex vivo prime edited autologous hematopoietic stem cell product, PM359, using proof-of-concept data from the first two patients treated in its phase 1/2 study.

“Prime Medicine continues to engage with the U.S. FDA to explore ways to make PM359 available to patients with chronic granulomatous disease (CGD),” the company stated in its 2025 financial report. Based on recent interactions with the agency, Prime says it believes the two-person clinical data generated to-date may be sufficient to support an accelerated approval and that the company is working towards final alignment with the FDA to submit a BLA.

Prime announced positive initial data from the first patient dosed with PM359 in CGD last May. Shortly after, the company cut a quarter of its workforce and revealed a pipeline reprioritization which involved exploring options for the continued clinical development of PM359 external to the company and ceasing further efforts in X-linked CGD.

Despite that, the company now sees a path to approval for PM359 in CGD, a rare inherited disease that leads to recurrent, debilitating and often life-threatening infections.

The FDA has promised a more flexible approach to overseeing chemistry, manufacturing and control (CMC) requirements for cell and gene therapies, with the goal of expediting product development. The agency recently published draft guidance for personalized therapies, outlining the use of its plausible mechanism framework. Yet, recent decisions, such as recommending that uniQure conduct a sham surgery-controlled study for its Huntington’s gene therapy, have given the industry pause.