The FDA has approved mepolizumab (Nucala, GlaxoSmithKline) for the treatment of patients aged 12 years and older with hypereosinophilic syndrome (HES). 

HES is a group of rare disorders associated with higher than normal levels of a type of disease-fighting white blood cell with evidence of organ damage. Symptoms of HES include rashes, itching, asthma, difficulty breathing, abdominal pain, vomiting, muscle inflammation, and congestive heart failure. 

Mepolizumab was evaluated in a randomized, double-blind, multicenter, placebo-controlled trial that included 108 patients with HES. Patients either received a placebo or mepolizumab by injection every 4 weeks for 32 weeks. Investigators defined an HES flare as worsening of clinical signs and symptoms or increasing eosinophils (disease-fighting white blood cells) on at least 2 occasions. 

Fifty-six percent of the placebo group had an HES flare-up, whereas 28% of patients in the mepolizumab group had a flare-up, according to the study. Additionally, the average time to the first HES flareup was later for the mepolizumab group than the placebo group, according to the study. 

“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,” Ann Farrell, MD, director of the Division of Nonmalignant Hematology in the FDA’s Center for Drug Evaluation and Research said in a press release. “FDA is committed to helping develop safe and effective treatment options for this group of rare and debilitating blood diseases and other rare conditions.”

Common adverse effects of mepolizumab included upper respiratory tract infection and pain in extremities. Additionally, herpes zoster occurred in some patients receiving mepolizumab. Health providers should consider vaccination if it is medically appropriate. 

Reference:
FDA Approves First Drug to Treat Group of Rare Blood Disorders in Nearly 14 Years [News Release] September 25, 2020; Silver Spring, MD. https://www.fda.gov/news-events/press-announcements/fda-approves-first-drug-treat-group-rare-blood-disorders-nearly-14-years?utm_medium=email&utm_source=govdelivery. Accessed September 28, 2020