FDA Approves First Ever Drug to Treat Hypereosinophilic Syndrome

"Today's approval marks the first time in over a decade that there is a new FDA-approved treatment option for patients with hypereosinophilic syndrome," said Ann Farrell, M.D., director of the Division of Nonmalignant Hematology in the FDA's Center for Drug Evaluation and Research. "FDA is committed to helping develop safe and effective treatment options for this group of rare and debilitating blood diseases and other rare conditions."

HES is a heterogeneous group of rare disorders associated with persistent eosinophilia (higher than normal levels of a type of disease-fighting white blood cell) with evidence of organ damage. Symptoms include skin rashes, itching, asthma, difficulty breathing, abdominal pain, vomiting, diarrhea, arthritis, muscle inflammation, congestive heart failure, deep venous thrombosis (blood clots in the veins) and anemia.

Nucala was evaluated in a randomized, double-blind, multicenter, placebo-controlled trial in 108 patients with HES. In the study, patients were randomly assigned to receive Nucala or placebo by injection every four weeks. The trial compared the proportion of subjects who experienced a HES flare during the 32-week treatment period. A HES flare was defined as worsening of clinical signs and symptoms of HES or increasing eosinophils (disease-fighting white blood cells) on at least two occasions. The trial compared the proportions of patients with at least one flare over a 32-week treatment period, as well as the time to the first flare. Fewer patients in the Nucala treatment group (28%) had HES flares compared to patients in the placebo group (56%), with a 50% relative reduction. In addition, the time to the first HES flare was later, on average, for patients treated with Nucala vs. placebo.

The most common side effects of Nucala in patients with HES include: upper respiratory tract infection and pain in extremities (such as the hands, legs and feet).

Nucala should not be administered to patients with a history of hypersensitivity to mepolizumab or one of its ingredients.

Herpes zoster (shingles) infections have occurred in patients receiving Nucala. Health care providers should consider vaccination if medically appropriate.

For the treatment of HES, Nucala received orphan drug designation, which provides incentives to assist and encourage drug development for rare diseases. Additionally, the application was granted fast track designation and priority review.

Nucala is also FDA-approved for patients aged 6 years and older with severe asthma with an eosinophilic phenotype and for adult patients with eosinophilic granulomatosis with polyangiitis, a rare autoimmune condition that causes blood vessel inflammation.