- The European Medicines Agency last week recommended an experimental gene therapy from GlaxoSmithKline for the treatment of an ultra-rare immune disorder which compromises the ability of affected children to fight off diseases. Infants born with the disorder, known as ADA-SCID, have almost no immunity against everyday infections.
- ADA-SCID is caused by a faulty gene inherited from both parents which prevents the body from producing a critical enzyme. Without this enzyme, toxins build up and destroy infection-fighting cells called lympochytes. GSK's therapy, marketed as Strimvelis, helps restore the body's immune system.
- Although no price has been released, GSK's rare disease head Martin Andrews told the Financial Times that GSK would permit staggered payments for the therapy. Another gene therapy called Glybera, conditionally approved in the E.U. in 2012, costs roughly $1 million per patient.
Strimvelis will fill a critical unmet medical need if it receives final marketing approval from the European Commission. ADA-SCID, or adenosine-deaminase-deficient severe combined immunodeficiency, normally proves fatal within the first two years of an infant's life unless immune function is restored.
Current treatment options are limited to stem cell transplantations from the bone marrow of a healthy donor or enzyme replacement therapy. Transplantations between genetically-matched siblings have been successful, but other nonmatched transplants have lead to graft versus host disease. Enzyme replacements, on the other hand, must be done weekly and have shown diminishing efficacy over time. They are administered under compassionate use in the E.U.
Glaxo's therapy is developed from the patient's own bone marrow cells, which are extracted and then inserted with the missing enzyme. After being reintroduced into the patient's body, the edited cells are able to develop into blood and immune cells key for fighting infection. By using the patient's own cells, the risk of graft versus host disease is dramatically reduced and less chemotherapy is needed prior to treatment. The gene therapy also sidesteps the hurdle of finding an appropriate donor for a bone marrow transplant.
All 12 people participating in a pivotal clinical trial of Strimvelis are still alive, with an average follow-up time of seven years. The first patient received the gene therapy more than 13 years ago.
Reports indicating GSK would permit staggered payments could help address the likely significant cost of Strimvelis. The personalized and intensive nature of the treatment, as well as the small patient population, would probably increase the price GSK would have to charge. Adding to pricing decision complexity, Strimvelis is administered only once rather than as a series of treatments.
The EMA recommended Strimvelis for patients for whom no gene-matched stem cell donor was available. Strimvelis' application will now go to the European Commission for final marketing approval.