FDA Clears First Human Thymus Transplant Tissue for Kids with Congenital Athymia

Rethymic, a cultured human thymus tissue developed by Enzyvant, has won FDA approval as the first-ever thymus tissue transplant product approved in the U.S.

The approval is the first real hope for children born with congenital athymia — the absence of the thymus gland, also called DiGeorge Syndrome. Most die within the first two or three years of life from overwhelming infections. The condition is extremely rare, affecting no more than 24 infants born each year in the U.S.

Derived from processed, cultured donor thymus, Rethymic is surgically implanted into the anterior thigh muscle, which provides a rich blood supply for nutrition and oxygenation. The tissue engrafts and begins producing T-cells within a few months, although it takes a year or more to reach the full immune potential.

Rethymic has been evaluated in 105 children in 10 open-label studies beginning in 1993. Of these, 29 patients died, including 23 deaths in the first year after implantation. The longest follow-up time is now more than 25 years.