A Functional Cure
A CRISPR-based gene therapy called exa-cel has achieved what researchers are cautiously calling a functional cure for sickle cell disease. All 42 patients enrolled in a phase 3 trial have been free of the severe pain crises caused by the disease, with the longest-followed patient now five years post-treatment with no recurrence.
How It Works
Sickle cell disease is caused by a mutation in the HBB gene that distorts red blood cells into a rigid crescent shape. Exa-cel uses CRISPR to reactivate a foetal haemoglobin gene that is normally switched off after birth, effectively replacing the defective haemoglobin with a functional form.
- Patients receive a single treatment — there are no ongoing injections or drugs.
- The therapy takes approximately 6 months from cell collection to infusion.
- Current cost: approximately $2.2 million per patient.
"Forty-two for forty-two. We have never seen anything like this in sickle cell disease. Five years of follow-up and not a single crisis. These people have their lives back," said the trial's principal investigator.
