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Cell & Gene Therapy Insights

Cell & Gene Therapy Insights

CRISPR gene editing shows promise in treating blood disorders

Interim data from two ongoing Phase 1/2 studies of CRISPR Therapeutics – Vertex research collaboration has yielded encouraging results for CTX001, an investigational ex vivo CRISPR gene-edited therapy developed for patients suffering from β-thalassemia and sickle cell disease.

CTX001 is an autologous stem cell therapy which leverages CRISPR editing to engineer a patient’s hematopoietic stem cells to produce high levels of oxygen carrying fetal hemoglobin (HbF). The therapy is being tested and is expected to treat sickle cell and β-thalassemia patients who are currently dependant on regular blood transfusions.

CTX001 is currently being tested in two Phase 1/2 studies, for treating patients with 1) transfusion-dependent beta thalassemia (TDT) and 2) sickle cell disease (SCD). Preliminary data obtained from one patient each from these trials has shown that the treatment is safe and effective.

In the two years ahead of starting the trial, the TDT patient needed an average of 16.5 blood transfusions per year and the SCD patient experienced seven vaso-occlusive crises per year—a common complication of SCD where blood cells stick together and block blood vessels, damaging tissues and organs.

The TDT patient received CTX001 in the first quarter of 2019 and nine months after receiving the treatment, the patient no longer needed transfusions and had near-normal hemoglobin levels. The SCD patient received CTX001 in mid-2019 and four months after administering the therapy, the patient was free of vaso-occlusive crises and had similar hemoglobin levels. Both patients also had high levels of red blood cells expressing fetal hemoglobin—more than 99% for the former and more than 94% for the latter—a sign that the CRISPR-edited treatment did what it was designed to do.

The treatment was safe and although serious adverse events occurred in both patients, none of them were related to CTX001.

Both trials (CLIMB-Thal-111 in TDT patients and CLIMB-SCD-121 for severe SCD patients) will enroll up to 45 patients and follow patients for approximately two years after infusion. Enrollment is ongoing at several clinical trial sites in the US, Canada and Europe.

CTX001 is being developed under a co-development and co-commercialization agreement between CRISPR Therapeutics and Vertex which was signed in 2015. Following the news, Vertex’s stock rose up 2.3% and that of CRISPR Therapeutics jumped 17%.

Dr Samarth Kulkarni, CEO of CRISPR Therapeutics commented: “We are very encouraged by these preliminary data, the first such data to be reported for patients with beta thalassemia and sickle cell disease treated with our CRISPR/Cas9 edited autologous hematopoietic stem cell candidate, CTX001. These data support our belief in the potential of our therapies to have meaningful benefit for patients following a one-time intervention. We continue to enroll these studies as we drive forward to develop CRISPR/Cas9 therapies as a new class of transformative medicines to treat serious diseases.”

Source: Vertex, CRISPR’s gene-editing treatment for blood disorders shows promise in early data; Website

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