The U.S. Food and Drug Administration (FDA) has approved Rethymic (allogeneic processed thymus tissue-agdc) for the treatment of pediatric patients with congenital athymia. This is the first targeted therapy approved for this condition.

Congenital athymia is a rare immune disorder in which a child is born without a thymus. Children impacted by this disease typically die within the first two years of life and may have repeated, often life-threatening infections because they lack adequate working T cells.

Rethymic is composed of human allogeneic thymus tissue that is processed and cultured, and then implanted into patients to help reconstitute immunity in patients who are athymic. Dosing is patient customized, determined by the surface area of the Rethymic slices and the body surface area of the patient.

The approval of Rethymic is based on the results of 10 prospective clinical studies involving 105 patients, ranging in age from one month to 16 years, who received a single administration of Rethymic. Rethymic improved survival of children with congenital athymia, and most children treated with this product survived at least two years. Children treated with Rethymic who survive past the first year generally survive long-term. Rethymic also reduced the frequency and severity of infections over time.

The Kaplan-Meier estimated survival rates based on data from 95 patients from those clinical studies shows survival rates of 77% (0.670–0.841) at one year and 76% (0.658–0.832) at two years.

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

The approval also provides the developers of the orphan drug a Rare Pediatric Disease Priority Voucher. Such vouchers can be used by the company (Enzyvant Therapeutics) for future medications or sold to other companies. Recently, Eiger Biopharmaceuticals sold their voucher for $95 million.

To learn more about congenital athymia and other rare autoimmune disorders, visit