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Clinical Trials Okayed for Sickle Cell Gene Editing

Sickle cell illustration

Sickle cell illustration (National Heart, Lung, and Blood Institute)

16 May 2018. Two companies developing therapies for inherited blood disorders say the Food and Drug Administration approved their application to begin clinical trials of treatments for sickle cell disease with gene editing. Bioverativ, a division of drug maker Sanofi in Waltham, Massachusetts, and Sangamo Therapeutics in Richmond, California received approval from FDA for its investigational new drug application, allowing clinical trials to begin of their treatment for sickle cell disease code-named BIVV003.

Sickle cell disease is a genetic blood disorder affecting hemoglobin, a protein in blood that delivers oxygen to cells in the body. People with sickle cell disease have hemoglobin molecules that cause blood cells to form into an atypical crescent or sickle shape. That abnormal shape causes the blood cells to break down, lose flexibility, and accumulate in tiny capillaries, leading to anemia and periodic painful episodes. Sickle cell disease is prevalent worldwide, and affects 70,000 to 80,000 people in the U.S., including about 1 in 500 people of African descent.

Bioverativ is a developer of therapies for blood disorders, focusing initially on hemophilia. The company’s pipeline also has a treatment in late-stage clinical trials for cold agglutinin disease, a rare form of anemia where the immune system mistakenly attacks red blood cells. As reported by Science & Enterprise in January 2018, Sanofi acquired Bioverativ in a deal valued at $11.6 billion.

Sangamo develops gene therapies, including gene editing with a technology that predates Crispr, known as zinc-finger nucleases. In zinc-finger nucleases, synthetic enzymes modify DNA sequences, including corrections or insertions. These enzymes, with a hydrocarbon and zinc chemistry, branch out in finger-like protrusions that bind with DNA molecules. Sangamo says it engineers the proteins to predictably and consistently bind with longer DNA sequences.

BIVV003 is being developed as therapies for sickle cell disease and beta thalassemia, another inherited blood disorder. The treatments use gene editing to modify the BCL11A gene, which regulates the level of fetal hemoglobin, in a patient’s own blood-forming stem cells. The stem cells are isolated from the blood, then the BCL11A genes are edited with zinc-finger nucleases. After conditioning the patient’s bone marrow, where blood cells are produced, the edited stem cells are infused back into the patient, where they’re expected to produce healthy hemoglobin.

Bioverativ and Sangamo plan to test BIVV003 in a combined early- and intermediate-stage clinical trial. The companies recently began a similar study of a therapy code-named ST-400 using edited blood-forming stem cells to treat beta-thalassemia. That study is enrolling 6 patients to test the treatments’ safety, but also their effects on fetal hemoglobin levels.

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