The US Food and Drug Administration today approved Gamifant (emapalumab) for the treatment of pediatric (newborn and above) and adult patients with primary hemophagocytic lymphohistiocytosis (HLH) who have refractory, recurrent or progressive disease or intolerance with conventional HLH therapy. This FDA approval is the first for a drug specifically for HLH.

“Primary HLH is a rare and life-threatening condition typically affecting children and this approval fills an unmet medical need for these patients,” said Richard Pazdur, MD, director of the FDA’s Oncology Center of Excellence and acting director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research. “We are committed to continuing to expedite the development and review of therapies that offer meaningful treatment options for patients with rare conditions.”

HLH is a condition in which the body’s immune cells do not work properly. The cells become overactive releasing molecules, which leads to inflammation. The immune cells start to damage the body’s own organs, including the liver, brain and bone marrow. It can be inherited, which is known as primary or “familial” HLH. It can also have non-inherited causes. People with primary HLH usually develop symptoms within the first months or years of life. Symptoms may include fever, enlarged liver or spleen and decreased number of blood cells.

The efficacy of Gamifant was studied in a clinical trial of 27 pediatric patients with suspected or confirmed primary HLH with either refractory, recurrent or progressive disease during conventional HLH therapy or who were intolerant of conventional HLH therapy. The median age of the patients in the trial was 1 year old. The study showed that 63% of patients experienced a response and 70% were able to proceed to stem cell transplant.

Common side effects reported by patients receiving Gamifant in clinical trials included infections, hypertension, infusion-related reactions, low potassium and fever. Patients receiving Gamifant should not receive any live vaccines and should be tested for latent tuberculosis. Patients should be closely monitored and treated promptly for infections while receiving Gamifant.

The FDA granted this application Priority Review and Breakthrough Therapy designation. Gamifant also received Orphan Drug designation, which provides incentives to assist and encourage the development of drugs for rare diseases.