FDA

Gamifant approved for macrophage activation syndrome in Still’s disease

July 2, 2025

FDA approved Gamifant (emapalumab-lzsg), an interferon gamma neutralizing antibody, for the treatment of adult and pediatric (newborn and older) patients with hemophagocytic lymphohistiocytosis (HLH)/macrophage activation syndrome (MAS) in known or suspected Still’s disease, including systemic juvenile idiopathic arthritis (sJIA), with an inadequate response or intolerance to glucocorticoids, or with recurrent MAS.

Gamifant had previously been approved for the treatment of adult and pediatric patients with primary HLH with refractory, recurrent or progressive disease or intolerance with conventional HLH therapy.

Efficacy

Approval was based on pooled data from 2 open-label, single arm trials: the phase 2 NI-0501-06 study (NCT03311854) and the phase 3 EMERALD trial (NCT05001737). Both studies evaluated emapalumab in children and adults (range, 0.9 to 64 years) with HLH/MAS in Still’s disease, including sJIA, with an inadequate response to high-dose glucocorticoid treatment. Results showed that 53.8% (21/39) of patients had a complete response at week 8, and 82.1% (32/39) achieved clinical MAS remission (VAS ≤1 cm) at week 8.

Safety

In patients with HLH/MAS in Still’s disease, the most common adverse events (≥20%) were viral infections, including CMV infection or reactivation, and rash.

Sources:

Gamifant (emapalumab-lzsg) [package insert]. Food and Drug Administration. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/761107s018lbl.pdf Revised June 2025. Accessed July 1, 2025.

FDA approves Gamifant® (emapalumab-lzsg) as first-ever treatment for adults and children with macrophage activation syndrome in Still’s disease. [News release]. 2025. https://www.sobi.com/en/press-releases/fda-approves-gamifantr-emapalumab-lzsg-first-ever-treatment-adults-and-children-macrophage-activation-syndrome-stills-disease-2342991