Gene Therapy Restores Immune Function

According to a study published in the New England Journal of Medicine last month, researchers have successfully treated children with a rare genetic immunodeficiency disorder called ADA-SCID using an investigational gene therapy. The results stem from three different Phase 1/2 trials—two in the US and one in the UK. 

ADA-SCID, or severe combined immunodeficiency due to adenosine deaminase deficiency, is a rare and life-threatening condition caused by mutations in the ADA gene that affect protein function, impairing immune function. Current treatment consists of enzyme replacement therapy, but this treatment does not lead to a fully functional immune system. Stem cell transplants can also offer relief, but many patients do not find donors.

The trials for the study used a lentiviral gene therapy—safer and more effective than previous gene therapies developed to treat ADA-SCID—to reintroduce a healthy copy of ADA into patients’ own hematopoietic stem cells, which are then infused back into the patient. The genetically modified stem cells then migrate to the bone marrow to produce new immune cells with healthy copies of ADA. 

The UK trial included 20 patients from four months to 16 years of age, while the US trials included 30 patients from four months to four years of age. Two to three years after being treated, 48 out of the 50 participants retained immune function and were able to cease enzyme replacement treatments.

 Despite mild to moderate side effects due to chemotherapy prior to transplant, overall, the treatment was found to be safe and another trial has begun at the Zayed Centre for Research into Rare Diseases in Children in London, UK. The gene therapy has not yet been approved by a regulatory authority.