ASH Report: Early Results from CTX001 Gene Editing Study

December 6, 2020 – CRISPR Therapeutics and Vertex Pharmaceuticals have announced early results from their CLIMB Thal-111 Study in which transfusion-dependent beta thalassemia patients are treated with a gene editing therapy called CTX001. CTX001 is a therapy that involves CRISPR/Cas9 gene editing of a patient’s own hematopoietic stem cells (HSCs) in order to reactivate fetal hemoglobin production. The results of the first seven patients treated in the CLIMB Thal-111 Study are now available:

All seven patients demonstrated increases in total hemoglobin and in fetal hemoglobin, and stopped receiving red blood cell transfusions soon after CTX001 infusion. The first thalassemia patient who received CTX001 has remained transfusion-free for 18 months as of this writing. Three of the seven patients who became transfusion independent had severe genotypes, including B0/B0.

The safety profile after CTX001 infusion was generally consistent with myeloablation using busulfan. One patient experienced several serious adverse events including headache, hemophagocytic lymphohistiocytosis (HLH), acute respiratory distress syndrome, and idiopathic pneumonia syndrome. All 4 of these adverse events occurred in the context of HLH and have resolved. No other CTX001-related serious adverse events were reported.

CLIMB Thal-111 is currently enrolling patients ages 12 to 35 with transfusion-dependent beta thalassemia – including those with homozygous β-thalassemia or hemoglobin E (HbE), with a history of ≥10 units/year of packed RBC transfusions in the prior 2 years. Patients may enroll in this study at one of the following 3 U.S. trial sites: (1) The Children’s Hospital at TriStar Centennial Medical Center/ Sarah Cannon Center for Blood Cancers in Nashville, TN; (2) Columbia University in NYC; and (3) Stanford University. Further information about the study is available at:

Further information about these early, positive trial findings is available in the press release at:

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