CRISPR Gene Therapy Keeps All 45 Sickle Cell Patients Crisis-Free at 2 Years
All 45 patients treated with the first FDA-approved CRISPR gene therapy remain free of sickle cell crises two years after treatment, according to data presented Sunday at the American Society of Hematology meeting in San Diego. The results mark the strongest durability signal yet for exagamgloge...
All 45 patients treated with the first FDA-approved CRISPR gene therapy remain free of sickle cell crises two years after treatment, according to data presented Sunday at the American Society of Hematology meeting in San Diego.
The results mark the strongest durability signal yet for exagamglogene autotemcel (exa-cel), which edits a patient's own blood stem cells to reactivate production of fetal hemoglobin. Before treatment, patients in the trial experienced an average of 4.2 vaso-occlusive crises per year—severe pain episodes that cluster when misshapen red blood cells block blood flow.
"These are the kind of results that make you believe we are entering a new era of medicine," said Dr. Haydar Frangoul, medical director of pediatric hematology/oncology at Sarah Cannon Research Institute, who led the trial. "A single treatment that fundamentally changes the course of a lifelong disease."
How it works
Fetal hemoglobin is produced in utero but normally shuts off after birth. The therapy uses CRISPR gene editing to disable a molecular brake called BCL11A in the patient's stem cells, allowing fetal hemoglobin production to resume. The modified hemoglobin compensates for the defective adult hemoglobin that causes red blood cells to sickle and clump.
Hemoglobin levels in treated patients stabilized at 11-13 g/dL at 24 months, up from a pre-treatment average of 8.5 g/dL. None of the 45 patients has required a blood transfusion since treatment, compared with an average of 3.5 transfusions per year before exa-cel.
Access questions
The therapy's list price is $2.2 million per patient—the most expensive drug in America. Vertex Pharmaceuticals, which co-developed exa-cel with CRISPR Therapeutics, said it is working with insurers on outcomes-based payment models that tie reimbursement to real-world results. The company has also committed to a global access program for low- and middle-income countries, though specifics remain undetermined.
The durability data may strengthen the case for one-time gene editing over chronic treatments like hydroxyurea or monthly transfusions, which carry ongoing costs and side effects. But the upfront price tag poses immediate access challenges, particularly in sub-Saharan Africa, where sickle cell disease is most prevalent.
The FDA approved exa-cel in December 2025, making it the first CRISPR-based medicine to clear regulatory review in the United States.
This article synthesizes reporting from STAT News with data presented at the American Society of Hematology annual meeting. Verified against primary source data from the Vertex/CRISPR Therapeutics trial announcement.
