The phrase "functional cure" is used carefully in medicine — it describes an outcome in which a disease's effects are so effectively suppressed that the patient lives as though they do not have it, even if the underlying genetic cause remains. For sickle cell disease, a condition that has caused lifelong suffering, organ damage, and premature death for 100,000 Americans and millions globally, achieving a functional cure through gene editing is one of the most profound accomplishments medicine has produced in years.
The RUBY Trial, published in the New England Journal of Medicine on April 1, 2026, has delivered exactly that result. Of 28 patients with severe sickle cell disease who were treated with renizgamglogene autogedtemcel (reni-cel) — a CRISPR-Cas12a gene editing therapy that modifies patients' own blood-forming stem cells — 27 (96 percent) had no painful sickle cell crises for up to two years following treatment. Their average hemoglobin levels rose to near-normal levels, effectively restoring the oxygen-carrying capacity that sickle-shaped red blood cells cannot provide.
