For those too young to remember, David Vetter, the original ‘Bubble Boy,’ was born in 1971 and almost immediately became the darling of the media. David had severe combined immunodeficiency (SCID), which left him defenseless against common infections that typically are controlled by a normal immune system but that could have proven fatal to him. David lived in a specially designed, sealed, plastic bubble until age 12 when he died of cancer, 4 months after receiving a bone marrow transplant from his sister.
Dr. Donald Kohn, a renowned stem cell researcher at the University of California Los Angeles, has been working with adenosine deaminase (ADA)‒deficient SCID for more than 30 years. He and his team have developed a gene therapy that in clinical trials has repaired and restored the immune system in children with ADA-SCID by using the child’s own stem cells, thus avoiding graft-versus-host and other autoimmune rejection problems that result in therapeutic failure.
Of all children with SCID, approximately 15% are deficient in ADA, an enzyme required for normal function and proliferation of infection-fighting lymphocytes. The only currently available therapies are twice-weekly ADA injections for life, which are expensive and often inadequate, and bone marrow transplants from siblings, matches for which are rare and can result in rejection. Using a virus delivery system developed in his laboratory in the 1990s, Kohn and his team developed a technique for removing the bone marrow of patients with ADA-SCID and replacing the defective ADA gene with a corrected gene. The corrected gene enables ADA protein production and, when transplanted to the patient, enables restoration of the immune system, including healthy T-cell, B-cell, and antibody production.
Kohn and his team continued refining their protocol, and through the course of 2 clinical trials since 2009 that included 18 patients, all have been cured. The team’s next step is filing for FDA approval of their gene therapy technique. They also plan to adapt their technique to sickle cell disease. Clinical trials in patients with sickle cell disease are already scheduled for later this year.
Contributed by William Yarnall, RPh, CCP
Medical Writer, Connexion Healthcare