Initial data from the phase 1/2 RUBY trial support the efficacy and safety of EDIT-301 in patients with severe sickle cell disease (SCD).

“These promising clinical results from the RUBY trial suggest clinical proof of concept for EDIT-301 and support our belief that EDIT-301 can be a clinically differentiated, one-time, durable medicine that can provide life-changing clinical benefits to patients with severe sickle cell disease long term,” Baisong Mei, MD, PhD, senior vice president and chief medical officer of Editas Medicine, said in a news release.

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The first patient treated with EDIT-301 achieved neutrophil and platelet engraftment at 23 and 19 days postinfusion, respectively. At 5 months post-treatment, the patient’s total hemoglobin level was 16.4 g/dL and their fetal hemoglobin (HbF) level was 45.4%.

The increase in HbF was highly pancellular, revealing a steady increase in F cells to levels greater than 95% of red blood cells. Moreover, the patient presented with a mean corpuscular HbF level of 13.8 pg/red blood cell, a value above the threshold required to suppress red blood cell sickling (10.0 pg/red blood cell).

The second patient achieved neutrophil and platelet engraftment at 29 and 37 days after EDIT-301 infusion.

EDIT-301 was well tolerated, and neither patient reported any vaso-occlusive events since treatment with EDIT-301 after 5 months (patient 1) and 1.5 months (patient 2). Furthermore, no serious adverse events or treatment-related adverse events occurred. The safety profile of EDIT-301 was consistent with that of myeloablative conditioning with busulfan and autologous hematopoietic stem cell transplant.

EDIT-301 is an experimental cell therapy that uses a novel gene-editing nuclease aiming to increase the expression of HbF. It is under investigation for the treatment of severe SCD and transfusion-dependent beta thalassemia.


Editas Medicine announces positive safety and efficacy data from the first two patients treated in the RUBY trial of EDIT-301 for the treatment of severe sickle cell disease. News release. Editas Medicine, Inc; December 6, 2022.