Millions of people around the world, including around 100,000 in the United States, suffer from sickle cell disease, a brutally painful inherited blood disorder. Most of them are of African descent. Over time, the disease worsens and can cause infections, organ damage, blindness, stroke, and early death.
“I can’t think of a more miserable disease than sickle cell,” James Taylor, director of the Howard University Center for Sickle Cell Disease in Washington, D.C., tells OneZero.
In the United States, sickle cell patients have long endured poor care and discrimination because of deep-rooted inequities in health care. A cure for the disease currently exists but is out of reach for many patients. A recent boom in sickle cell research, however, could make a cure available to many more people. New results from two experimental genetic treatments show promise for eliminating the disease.
Sickle cell arises from a mutation in a gene that makes a critical blood protein called hemoglobin. People who inherit this mutation from both parents have an abnormal form of hemoglobin that produces sickle-shaped red blood cells instead of healthy round ones. These sickled blood cells clump together in the bloodstream and cause painful episodes lasting hours or days. People with sickle cell frequently end up in the hospital because of these bouts of pain, and many need regular blood transfusions to provide normal blood cells to the body.
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“These patients could die during any one of those hospitalizations, and they live with that sword hanging over their head,” Samarth Kulkarni, CEO of CRISPR Therapeutics, tells OneZero. “After having our treatment there have been no hospitalizations to date.”
In a pioneering clinical trial run by CRISPR Therapeutics and Vertex Pharmaceuticals, a single infusion of genetically modified cells has eliminated severe symptoms of sickle cell in one woman with the disorder. The cells were modified by using the gene-editing tool CRISPR to switch on a gene in the patients’ blood stem cells so that they could make healthy hemoglobin. To do this, doctors first remove these cells from the body then send them off to a manufacturing facility to be edited with CRISPR. After that, scientists perform several safety tests on the cells, freeze them, then transport them back to the hospital. Once thawed, the cells are infused back into the person, where they can grow into healthy new blood cells.
Victoria Gray, whose story has been documented by NPR, has had no pain crises for nine months since her treatment. Gray had been hospitalized several times because of sickle cell complications the year before she received the gene-edited cells. CRISPR Therapeutics and Vertex Pharmaceuticals, which have since treated a second patient, presented the results at a virtual scientific meeting on June 12.
Biotech company Bluebird Bio is working on a different treatment for sickle cell. In a study of 25 people, the gene therapy seems to have eliminated major pain episodes and the need for blood transfusions in 18 people who have been followed for at least six months. The company announced the results on June 12.
That therapy also involves removing a patient’s blood stem cells and genetically modifying them. But instead of editing the cells, scientists use a technique that’s older than CRISPR. It involves infecting cells with viruses that are engineered to carry a working version of the malfunctioning gene. These cells are then infused back into the patient, where they should grow into healthy new blood cells. The approach has shown to be safe, although one person in the trial died suddenly more than a year after receiving the treatment. An independent study committee concluded that the death was due to cardiovascular problems and unlikely to be related to the gene therapy.
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