The U.S. Food and Drug Administration announced the approval of the first treatment for hypereosinophilic syndrome (HES) in more than a decade.
HES is defined by the Mayo Clinic as “a group of blood disorders that occur when you have high numbers of eosinophils — white blood cells that play an important role in your immune system. Over time, the excess eosinophils enter various tissues, eventually damaging your organs. The most common targets are the skin, lungs, digestive tract, heart, blood, and nervous system. Untreated, HES can become life-threatening.”
The newly approved drug, Nucala (mepolizumab), is approved for patients 12 years and older with HES for at least six months without another identifiable non-blood-related cause of the disease.
Approval was based on data from a phase 3 double-blind, multicenter, placebo-controlled trial of 108 patients with HES. In addition to standard-of-care treatment, patients were randomly assigned to Nucala 300 mg or placebo injections every four weeks for 32 weeks. HES flares, defined as at least two instances of worsening of clinical signs and symptoms of HES or increasing eosinophils, occurred in 28 percent of patients randomly assigned to Nucala versus 56 percent in the placebo group — a 50 percent relative reduction. Patients randomly assigned to Nucala also had a later time to first HES flare, on average, compared with those randomly assigned to placebo.
The most commonly reported side effects of Nucala included upper respiratory tract infection and extremity pain. Injection site reactions occurred in 7 percent of patients treated with Nucala versus 4 percent treated with placebo. The drug is contraindicated in patients with a history of hypersensitivity to mepolizumab. The FDA notes that herpes zoster infections have also occurred with Nucala, and health care providers should suggest patients be vaccinated if appropriate.
This recent approval of Nucala is in addition to its approval for severe asthma with an eosinophilic phenotype and for eosinophilic granulomatosis with polyangiitis in adults. Approval was granted to GlaxoSmithKline.