FDA Approves First Therapy for Rare Immune Disorder

Rethmyic is a one-time regenerative tissue-based therapy for children born without a thymus gland.

The FDA has approved Enzyvant Therapeutics’ Rethymic (allogeneic processed thymus tissue-agdc), a one-time therapy for immune reconstitution in pediatric patients with congenital athymia. Rethymic is engineered human thymus tissue designed to regenerate the thymic function.

Pediatric congenital athymia is ultra-rare with an estimated incidence of about 17 to 24 live births each year in the United States. Children who have this condition are born without a thymus. The thymus is part of the lymphatic system and plays a central role in the immune system. Children born with this condition are immune deficient and have high susceptibility to potentially fatal infections.

The approval was based on 10 single-arm studies conducted from 1993 to 2020 in a total of 105 patients, who were implanted with Rethymic. Survival rates were 77% at one year and 76% at two years. The most common adverse reactions include high blood pressure, cytokine release syndrome, low blood magnesium levels, rash, low platelets and graft-versus-host disease.

“This therapy is the result of more than 25 years of research aimed at increasing survival for patients who previously had very little hope,” Louise Markert, M.D, Ph.D., principal investigator for Rethymic clinical trials and professor of pediatrics and immunology at the Duke University School of Medicine, said in a statement. “Our research program was inspired each and every day by the possibilities that exist for children who have congenital athymia with an FDA-approved treatment for this devastating condition.”

The FDA has granted the therapy multiple designations including regenerative medicine advanced therapy, breakthrough therapy, rare pediatric disease, and orphan drug.