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Vertex, CRISPR strengthen case for pioneering gene-editing treatment

A gene editing medicine designed to treat two blood disorders has continued to perform strongly in clinical testing, with the latest results showing that, in the vast majority of treated patients, it alleviates the symptoms and burdens of both diseases.

Presented Saturday at a high-profile medical conference, the results represent another milestone for the therapy’s developers, Vertex Pharmaceuticals and CRISPR Therapeutics, which hope to ask for approval in the U.S., U.K. and Europe before the end of the year.

If approved, the therapy, now known as exa-cel, would become the first marketed medicine based on CRISPR, the landmark gene editing technology that won a Nobel Prize in 2020. It would also provide a new treatment option for patients with sickle cell disease or beta thalassemia.

While a small number of medications are cleared for use in these diseases, the only cure for them are stem cell transplants. The procedure is risky, though, and isn’t available to many patients. Exa-cel may serve as another, perhaps more attainable fix, especially if Vertex and CRISPR can keep generating supportive evidence.

So far, the companies have released data on 75 treated patients, almost all of whom are now living without the most serious and impactful effects of their illnesses.

In sickle cell, genetic mutations give rise to misshapen red blood cells, which cause painful and sometimes life-threatening blockages known as vaso-occlusive crises. Beta thalassemia, meanwhile, is also an inherited condition, but one that hinders production of an oxygen-carrying protein called hemoglobin. In severe cases, patients require regular blood transfusions to survive, which can lead to the toxic buildup of iron in their organs.

The trial data presented Saturday are from 31 patients with sickle cell and 44 with beta thalassemia who are dependent on blood transfusions. In the two years leading up to the study’s start, the sickle cell patients experienced about four severe vaso-occlusive crises annually, whereas those with beta thalassemia received, on average, 36 units of red blood cells.