Around 20 million people worldwide live with sickle cell disease or beta-thalassemia, two inherited blood disorders that had no reliable cure for decades. Research by Stuart Orkin and Swee Lay Thein changed that. Their discovery of the core mechanism controlling fetal hemoglobin production in the human body formed the scientific foundation for Casgevy, the world's first CRISPR/Cas9-based therapy to receive FDA approval. On April 18, 2026, Orkin and Thein received the Breakthrough Prize in Life Sciences in Los Angeles, $3 million in recognition of four decades of foundational research.
The Gene at the Center
The story begins in the 1980s. Swee Lay Thein, now a senior researcher at the National Heart, Lung and Blood Institute at the U.S. National Institutes of Health in Bethesda, observed that some adults retain unusually high levels of fetal hemoglobin. That observation mattered: fetal hemoglobin, produced by newborns in the first months of life, functions normally. The problem in sickle cell patients lies in adult hemoglobin, which forms an abnormal structure that creates rigid, sickle-shaped red blood cells. These block blood vessels, causing severe pain, organ damage and premature death.
Thein mapped the genetic cause of persistent fetal hemoglobin production to chromosome 2 and identified the gene BCL11A as the key factor. Stuart Orkin, a hematologist at Harvard Medical School, completed the picture: he showed how BCL11A acts as the master repressor, actively suppressing fetal hemoglobin production after birth. Switching off this repressor causes the body to resume producing fetal hemoglobin. The sickle-shaped cells are displaced and the disease's symptoms largely disappear.
How Casgevy Works
Casgevy was developed by Vertex Pharmaceuticals and CRISPR Therapeutics on the basis of this foundational research and received FDA approval in December 2023, making it the world's first CRISPR/Cas9-based medicine with regulatory clearance. Treatment proceeds in several steps: stem cells are extracted from the patient's bone marrow, edited in the laboratory to deactivate the BCL11A repressor, and then infused back into the body. Clinical trials showed that the large majority of treated patients became largely symptom-free. The FDA described the outcome as a functional cure.
The Breakthrough Prize, awarded annually in physics, mathematics and life sciences and among the most generously funded science awards in the world, honored not the therapy development itself but the decades of basic research that made it possible. Orkin and Thein were among several scientists recognized at the April 18 gala in Los Angeles.
The Limits of the Breakthrough
The constraints on access are significant. Casgevy costs around $2.2 million in the United States. Treatment takes up to a year and requires intensive chemotherapy to destroy existing bone marrow before the edited stem cells can be returned. Thein described the process as very demanding for patients.
The deeper problem is geographic. Sickle cell disease disproportionately affects people in sub-Saharan Africa, India, the Middle East and the Mediterranean region. In the areas with the highest disease burden, Casgevy is barely accessible. The cost and the medical infrastructure required exceed what most health systems in those regions can provide. In the United States, where the therapy is approved, around 100,000 people live with sickle cell disease, predominantly African Americans and Hispanic Americans.
What Comes Next
Long-term data from the first Casgevy treatments are expected over the course of 2026, showing how stable the curative effects remain over several years. Multiple research groups are working on cheaper CRISPR approaches that do not require bone marrow extraction, which would make treatment accessible in countries with limited medical infrastructure. The Breakthrough Prize for Orkin and Thein does more than honor the scientists: it brings four decades of foundational work, largely invisible to the public, the recognition it always deserved.