Prime Medicine, Inc. announced positive initial data from the first patient in its Phase 1/2 clinical study of PM359 for Chronic Granulomatous Disease (CGD), marking the first-ever clinical data supporting the safety and efficacy of Prime Editing in humans. A single dose of PM359 led to 58% dihydrorhodamine (DHR) positivity by Day 15 and 66% by Day 30 in neutrophils, significantly exceeding the 20% threshold believed to be potentially curative. This demonstrates the ability of Prime Editing to correct a pathogenic mutation and change the course of a life-limiting disease.
The patient also experienced rapid engraftment of autologous transplant, with neutrophils confirmed on Day 14 and platelets on Day 19. This engraftment rate is nearly two times faster than reported for approved gene editing technologies. PM359 was generally well-tolerated, with adverse events consistent with myeloablative conditioning and no serious adverse events related to the drug reported.
Despite these positive results, Prime Medicine stated it does not plan to independently advance its efforts in CGD and is exploring options for external clinical development of PM359. The company will cease further efforts in X-linked CGD and will focus its resources on its in vivo liver franchise, including Wilson’s Disease and Alpha-1 Antitrypsin Deficiency, as well as its Cystic Fibrosis program and partnership with Bristol Myers Squibb.
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