A patient with anemia cured by gene therapy

The announcement Wednesday of the healing of a man suffering from a serious genetic blood disease, thalassemia, is a major event.

This is the first time people managed to overcome gene therapy of congenital disease that affects millions of people. Nearly 200,000 children born each year worldwide with this disease.

Three years after treatment, the patient, living in France and now 21 years old, no longer needs to receive blood transfusions. The results published today in the British journal Nature are the result of a collaboration between several French teams (CEA, Assistance Publique, Paris-Sud University, Paris Descartes and Paris Diderot), American universities of Pennsylvania, the company Bluebird, with the support of Telethon and the French Association against Muscular Dystrophy control.

"The young French, Vietnamese and Thai whose gene correction had been administered at the age of 18 years has a form of the disease - called beta-E/beta-0 - common in Southeast Asia," says Prof. Marina Cavazzana-Calvo (Necker Hospital, Paris). This genetic defect causes a deformation of red blood cells, leading to their early destruction, anemia, and various disorders caused by an overload of iron in the body resulting in repeated transfusions.

The team of Professor Philippe Leboulch (ECA) had made nearly ten years ago the first correction of anemia gene in mice by gene therapy. It still took many years to develop a protocol for humans. Basically, it was first necessary to develop a lentivirus containing the corrected gene and totally harmless to humans.

The patient initially underwent a bone marrow stem cells which have been extracted. These stem cells were cultured with the modified lentiviruses so that the new gene was inserted into the heart of stem cells. Finally, the patient received chemotherapy to destroy his own diseased bone marrow. And 48 hours later, the modified stem cells have been reinfused intravenously. "The patient has remained about one month in hospital," says Dr. Eliane Gluckman, pioneer in bone marrow (Hôpital Saint-Louis, Paris). After eleven months, he no longer needed transfusions, notes Prof. Marina Cavazzana-Calvo. It is a great step forward but must be confirmed with other patients. "

Hemoglobinopathies (sickle cell anemia and beta-thalassemia) are the most common hereditary diseases. They are due to defects in the gene controlling the production of beta-globin gene, an essential component of hemoglobin that carries oxygen in red blood cells. In severe cases, patients survive anemic transfusion and treatment to remove excess iron that accumulates due to repeated transfusions.

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