CRISPR delivered a functional cure for severe sickle cell in 27 of 28 patients

Sickle cell disease turns red blood cells into rigid crescents that jam small vessels, causing episodes of extreme pain called vaso-occlusive crises. In a peer-reviewed trial published in the New England Journal of Medicine in April 2026, 27 of 28 patients with severe disease, 96%, had no such crises after a single CRISPR gene-editing treatment, and all had entered the trial with a history of recurrent severe crises.

How we know

The mechanism is elegant: the therapy edits a genetic switch so the body resumes making fetal haemoglobin, the form we produce before birth, which does not sickle. In treated patients, total haemoglobin rose to 13.8 grams per decilitre at six months, up from 9.8 at baseline, and fetal haemoglobin climbed to about 48% of the total. The trial was multi-centre, published in a top journal after peer review, with an effect size hard to misread, though median follow-up was under a year and one patient had not yet reached the follow-up needed to confirm engraftment at the data cutoff.

Why it matters

Patients still need harsh chemotherapy and a stem-cell transplant to receive the edited cells, which carry fertility and toxicity risks, and two serious adverse events were judged possibly related, though the paper reports them plainly, part of why it can be trusted. Functional cure is the right phrase, read precisely: freedom from crises at short follow-up, not yet a proven permanent fix. For a disease defined by pain and hospital visits, that absence of crises is close to the whole point, a stunning thing for a disease that has caused so much suffering for so long.