FDA Approves First Treatment for Rare Disease Congenital Athymia

FDA recently approved Rethymic to treat pediatric patients with rare disease congenital athymia. 

Congenital athymia is a rare immune disorder in which a child is born without a thymus. The thymus is an organ that plays a critical role in helping the body learn to fight infections. 

Children impacted by this disease typically die within the first two years of life and may have repeated, life-threatening infections due to a lack of adequate working T cells. 

Rethymic is the first thymus tissue product approved in the US.

“Today’s action marks the first FDA approval of a therapy to treat this very rare and devastating disease in children,” Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research, said in the announcement.

“We remain committed to helping advance the development of safe and effective medical products for patients affected by rare diseases – an area of such critical need,” Marks continued.

FDA based its approval on the safety and efficacy of Rethymic in clinical studies, which evaluated 105 patients aged one month to 16 years. Each participant received a single administration of Rethymic from 1993 to 2020.

In the trials, Rethymic improved the survival of children with congenital athymia. Most children treated with the drug survived at least two years, and those who survived past the first year generally survived long-term.

The most common adverse reactions in patients that received Rethymic included high blood pressure, cytokine release syndrome, low blood magnesium levels, rash, low platelets, and graft versus host disease.

Rethymic is composed of donor-derived thymus tissue that is processed, cultured, and then implanted into patients to help improve immune function in athymic patients.

Because Rethymic is derived from human tissue, it carries a risk of transmitting infectious disease, an FDA spokesperson explained. The risk of infectious disease transmission is remote but not completely eliminated.

With this FDA approval, Enzyvant obtained a Priority Review Voucher (PRV) under the Rare Pediatric Disease Program.

“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, MD, PhD, principal investigator for Rethymic clinical trials and professor of pediatrics and immunology at the Duke University School of Medicine, said in an official 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,” Markert concluded.