Prime editing restored a missing enzyme in its first patients

Prime Medicine and collaborating hospitals tested a therapy for a rare immune disease, chronic granulomatous disease, in two patients whose own blood stem cells were edited outside the body to fix the exact genetic error causing their condition, then infused back in.

The therapy used prime editing, a precise gene-editing technique, to correct a two-letter deletion in the NCF1 gene that leaves patients unable to make a working immune enzyme. After the edited stem cells engrafted, both patients showed restored enzyme activity in their neutrophils within one month, holding for six and four months at last follow-up.

Chronic granulomatous disease leaves patients prone to severe, recurring infections because their immune cells cannot kill certain bacteria and fungi, and the only established cure was a bone marrow transplant from a matched donor, which not every patient has. With two patients and a few months of follow-up, it is too early to call the treatment a cure. Longer follow-up and more patients will decide whether the correction lasts.

An exact gene correction, given back to two patients.