The concept of gene therapy is almost thirty years old. However, the approach has so far mostly been used to treat very rare diseases. In comparison, sickle cell disease affects 100,000 people in the United States alone. If the treatment is successful in larger trials, it could bring gene therapy into widespread use. Deborah Gill at the University of Oxford stated, “It could be a game changer. The fact the team has a patient with real clinical benefit, and biological markers to prove it, is a very big deal.”
Individuals with sickle cell disease produce abnormal versions of haemoglobin, the blood protein that carries oxygen around the body. This can be caused by mutations in the gene that makes a subunit of haemoglobin, called beta-globin. The mutations cause haemoglobin to clump together, distorting red blood cells into a sickle-shape that can get stuck in blood vessels around the body. Patients are given blood transfusions to clear these painful blockages and prevent new ones from occurring. Bone marrow transplants can treat the disease, but matching donors can only be found for around 10% of people with the disorder.
Now a team in France seems to have developed a treatment that would work for everyone with the condition. First, the team took bone marrow stem cells from a 13 year old boy and gave him extra, mutated versions of the gene that codes for beta-globin. These were designed to make beta-globin that would interfere with the boy’s faulty proteins, stopping them from clumping together. The scientists then put these stem cells back into the boy’s body. After around three months, he began producing large quantities of haemoglobin that behaves normally.
Marina Cavazzana at the Necker Children’s Hospital in Paris, who led the team stated, “The patient is now 15 years old and free of all previous medication. He has been free of pain from blood vessel blockages, and has given up taking opioid painkillers.” Cavazzana is confident these benefits will last. “All the tests we performed on his blood show that he’s been cured, but more certainty can only come from long-term follow-up.” She says her team has treated seven other patients, who are showing “promising” progress.