97 percent of treated patients remained permanently free from the life-threatening pain crises that made sickle cell disease incurable for decades. The discovery behind this result, a gene switch called BCL11A, has now earned its researchers the Breakthrough Prize: three million dollars for Stuart Orkin of Harvard Medical School and Swee Lay Thein of the US National Institutes of Health.
What Sickle Cell Disease Is
Sickle cell disease is a hereditary condition in which red blood cells take on a crescent shape, struggle to pass through narrow blood vessels and cause blockages. The consequences are recurring pain crises, organ damage, strokes and a significantly shortened life expectancy. Worldwide, 7.74 million people live with the disease; 515,000 newborns are born with it each year, 80 percent of them in sub-Saharan Africa. Beta-thalassemia, a related blood disorder, accounts for another 1.31 million severe cases globally.
For decades there was no cure. Blood transfusions, painkillers and the drug hydroxyurea helped manage symptoms but did nothing to address the underlying problem: defective hemoglobin inside blood cells.
The BCL11A Gene Switch
In 2007, Orkin and Thein independently discovered the same connection: the gene BCL11A acts as the master switch that shuts off fetal hemoglobin production after birth. Fetal hemoglobin is the healthy version of the protein every person produces as a fetus. In patients with sickle cell disease, continued production would compensate for the defective blood cells. BCL11A prevents that.
The insight was fundamental: blocking BCL11A prompts the body to resume producing fetal hemoglobin, and the sickle cells lose their dangerous shape. In mouse models, switching off BCL11A cured sickle cell disease entirely. Orkin and Thein had not just understood a mechanism; they had identified a direct therapeutic target.
Casgevy: The World's First CRISPR Therapy
On December 8, 2023, the US Food and Drug Administration approved Casgevy, developed by Vertex Pharmaceuticals and CRISPR Therapeutics. It is the first CRISPR/Cas9-based medicine ever approved for a genetic disease, indicated for both sickle cell disease and transfusion-dependent beta-thalassemia.
The procedure: stem cells are extracted from the patient's bone marrow and modified in the lab so that BCL11A is permanently suppressed in blood precursor cells. The modified cells are then reinfused. A single treatment is intended to last a lifetime.
In clinical trials, 44 patients were treated. Of the 30 patients with at least twelve months of follow-up, 29 remained completely free of severe pain crises, corresponding to 96.7 percent. In beta-thalassemia, 91 percent of patients achieved complete independence from blood transfusions.
Sixteen Years from Discovery to Therapy
Between the BCL11A discovery in 2007 and the FDA approval of Casgevy in 2023, sixteen years of research elapsed. By medical standards, that is comparatively fast: many foundational discoveries wait far longer for clinical translation, or never reach clinical practice at all.
The Breakthrough Prize is funded by technology entrepreneurs including Yuri Milner and Mark Zuckerberg and is considered one of the most generously endowed science prizes in the world. The award to Orkin and Thein in April 2026 highlights what is rarely so directly demonstrable: basic research without immediate application can transform millions of lives decades later.
The Central Problem: The Price
Casgevy costs $2.2 million per treatment in the United States. For the 80 percent of patients who live in sub-Saharan Africa, that is out of reach. Vertex and international health organizations are negotiating access programs for low-income countries; concrete outcomes remain pending.
In parallel, Orkin's team is working on small-molecule compounds that could block BCL11A orally or by injection, at far lower cost than the complex cell therapy. The team expects the first candidates to enter clinical testing within three to five years. Whether Casgevy becomes a blueprint for further CRISPR therapies depends in part on whether the technology becomes accessible to lower-income health systems.