Rethymic FDA-Approved for Congenital Athymia

Prior to October 8, 2021, there were no FDA-approved treatment options for pediatric patients with congenital athymia, an ultra-rare immune disorder. However, this all changed when the FDA approved Rethymic for this patient group. According to a news release, the treatment, developed by Enzyvant Therapeutics, Inc. (“Enzyvant”) is the first approved processed thymus tissue treatment within the country. This innovative product promotes the idea that additional treatment options can be created to improve patient outcomes and prevent early mortality. 

Congenital Athymia

According to Athymia Insights, pediatric congenital athymia is:

an ultra-rare immune disorder in which a child is born without a thymus [which] affects about 17 to 24 infants out of every 4 million born each year in the United States alone.

While the thymus does not operate for your entire life, it does provide benefits when it is working (up until puberty). The thymus regulates immune response and protects against autoimmune attacks. It also helps to produce T-lymphocytes (T cells), which help protect the body against viruses or infections, and a hormone called thymosin.

When children are born without a thymus, their bodies do not produce enough T cells. As a result, patients may experience severe, frequent, and life-threatening infections. Historically, this has caused many pediatric patients with congenital athymia to die before age 2. Additional symptoms may include hypoparathyroidism, heart defects, hypocalcemia, high levels of blood phosphorus, seizures, laryngomalacia, noisy breathing, and feeding difficulties.


Thus, treatments like Rethymic have the opportunity to significantly improve patient outcomes and quality of life. This processed allogeneic thymus tissue product is surgically implanted into pediatric patients. Through this, the product works to heighten immune function and prevent against the life-threatening infections. According to Enzyvant:

The recommended dose range is 5,000 to 22,000 mm2 of RETHYMIC/m2 recipient body surface area (BSA).

Because the product is made of human tissue, it is possible to pass along infectious diseases or other issues. However, Enzyvant believes that the risk of this happening is small (albeit not non-existent). Rethymic was shown to be both safe and efficacious within a clinical trial evaluating the treatment in 105 pediatric patients (aged 1 month-16 years). In addition to improving the survival rate, Rethymic treatment also lowered the risk of infections and prevented severe infections from occurring.

Altogether, Rethymic takes around 6+ months to improve immune function. While the treatment is safe, some side effects may occur, including thrombocytopenia (low platelet count), graft-versus-host disease (GvHD), low magnesium levels, rashes, and high blood pressure.

Jessica Lynn

Jessica Lynn

Jessica Lynn has an educational background in writing and marketing. She firmly believes in the power of writing in amplifying voices, and looks forward to doing so for the rare disease community.

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