A new gene therapy technique has been used to successfully reverse sickle cell disease for the first time ever. Although this is just one case study involving a single French teenager, the early signs are encouraging, and the therapy could eventually lead to an effective treatment for the millions of people with this crippling disease worldwide.
The teenager was prior to the treatment on a monthly blood transfusion to dilute his defective blood but at age 13, doctors at Necker Children’s Hospital in Paris decided to alter the genetic instructions in his bone marrow.
This was done through the injection of a virus (which corrected the defect he had) into his bone marrow. The altered bone marrow was then put back into the patient.
After 15 months of therapy, the patient is off medication, and while it’s far too early to say he’s been functionally cured, it’s a case of ‘so far so good’ for this pioneering kind of treatment.
Speaking to BBC, a professor of medicine at the University of Paris, said:
“So far the patient has no sign of the disease, no pain, no hospitalisation. He no longer requires a transfusion so we are quite pleased with that.
“But of course we need to perform the same therapy in many patients to feel confident that it is robust enough to propose it as a mainstream therapy.”
Sickle cell disease causes a condition called ischemia – an interruption of the flow of oxygen to parts of the body that causes pain, organ damage, and in some cases, eventually death. It results from a point mutation at amino acid position 6 in the beta globin gene that causes polymerization of the protein and sickling of the erythrocytes that contain it, under low-oxygen conditions, obstructing microcirculation and damaging organs.
The only existing long-term treatment is a bone marrow transplant, a high-risk and difficult operation that not everyone is eligible for.
But because sickle cell disease involves a mutation of just a small part of the body’s genetic code – producing an abnormal beta-globin protein known as haemoglobin S – it’s a prime candidate for genetic therapy treatments that could reverse the mutation.
Haemoglobin A (HbA) is the normal subunit; HbS is the one altered by the sickle cell mutation.
Hydroxyurea, which stimulates fetal haemoglobin production, is the only disease-modifying therapy for Sickle cell Disease; allogeneic haematopoietic stem cell transplant is curative.
Fewer than 18% of people with severe Sickle Cell find transplant matches. For them, autologous transplant with a corrected beta globin gene — gene therapy — is a tantalizing chance at a possibly one-time treatment.