Study summary

A CRISPR gene-editing treatment stopped pain crises in almost everyone

Exa-cel (Casgevy) trial · 44 treated, phase 3 · Published April 2024, New England Journal of Medicine; FDA approved December 2023, expanded to age 2 and up July 2026

97%free of pain crises for at least 12 months

What was tested

Exagamglogene autotemcel (Casgevy), in which a patient's own stem cells are edited with CRISPR to restart fetal hemoglobin production, given after high-dose chemotherapy, for severe sickle cell disease.

What they found

29 of 30 evaluable patients (97%) had no pain crises for at least 12 straight months.
All 30 were free of hospital stays for pain crises.
Requires myeloablative chemotherapy, with infertility and other risks.

What it means

A functional cure for many, but access is limited by cost, specialized centers and the intensity of the conditioning chemotherapy.

N Engl J Med, via PubMed ↗ ← Back to the outlook

Last reviewed 2026-11-14 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.