FDA Approves First Treatment for MAS in Still Disease

The FDA has approved the interferon gamma-blocking antibody emapalumab-lzsg (Gamifant) for the treatment of macrophage activation syndrome (MAS) in known or suspected Still disease.

This is the first FDA-approved treatment for MAS in the United States. The indication is specifically for adult and pediatric (newborn and older) patients with MAS in Still disease with an inadequate response or intolerance to glucocorticoids, or with recurrent MAS.

Emapalumab-lzsg was first approved in 2018 for adult and pediatric patients with primary hemophagocytic lymphohistiocytosis (HLH) with refractory, recurrent, or progressive disease or intolerance with conventional HLH therapy.

“With our expertise in primary hemophagocytic lymphohistiocytosis, we understand the urgency of managing MAS quickly to improve patient outcomes,” said Guido Oelkers, PhD, the CEO of the drug’s manufacturer, Sobi, in a press release. “Gamifant is already an established therapy making a meaningful difference for patients with primary HLH, and with this approval, we are excited about the opportunity to positively impact patients affected by MAS in Still’s disease.”

The approval for this indication was supported by pooled data from a phase 2 and a phase 3 clinical trial: More than half (54%) of participants had a complete response at week 8, and 82% achieved clinical MAS remission at week 8. 

“With Gamifant now as the first FDA-approved treatment for MAS, we have a new therapeutic option that helps control hyperinflammation and reduce our reliance on high-dose glucocorticoids,” added Alexei Grom, MD, professor of pediatrics and research director in the Division of Rheumatology at Cincinnati Children’s Hospital Medical Center, Ohio, in a press statement. 

Emapalumab-lzsg is administered via intravenous infusion and is available in 5-mg/mL and 25-mg/mL solutions in a single-dose vial. For this new indication, the most common side effects are viral infections, such as cytomegalovirus infection or reactivation, or rash.

Patients on emapalumab-lzsg should not receive live or live attenuated vaccines. Healthcare providers should consider prophylactic treatment for herpes zoster, Pneumocystis jirovecii, and fungal infections.