Swedish Orphan Biovitrum AB (Sobi®) has shared the news that Gamifant® (emapalumab-lzsg) has been granted approval by the U.S. Food and Drug Administration (FDA) for use in adult and pediatric patients with hemophagocytic lymphohistiocytosis (HLH) or macrophage activation syndrome (MAS) due to either known or suspected Still’s disease (including systemic Juvenile Idiopathic Arthritis (sJIA). The approval specifically targets patients who are unresponsive to glucocorticoids or have experienced relapses or intolerances to standard therapy.
The data supporting Gamifant’s expanded indication were based on a pooled analysis of two clinical trials, the Phase 3 EMERALD study and the NIH NI-0501-06 trial. In the analysis, 54% of patients achieved a complete response by the eighth week, and over 80% achieved clinical MAS remission. We found that the adverse events observed at the interim analysis were consistent with previously reported data, with relevant viral infections and skin rashes being the most frequently reported events.
“With our detailed knowledge of primary HLH, we understand the importance of timely intervention for MAS to avoid the risk of permanent damage,” said Guido Oelkers, Sobi CEO. “Gamifant has already transformed outcomes and renewed hope for primary HLH. With this success, we hope Gamifant can similarly provide that option for patients with MAS related to Still’s disease.”
HLH and MAS are rare but serious conditions that can result from runaway immune activation. MAS represents a severe hyperinflammatory manifestation of a rheumatic disease like Still’s disease in which the immune system is in an activated state, leading to overwhelming inflammation and sometimes organ failure. The presenting features of MAS include unremitting fever, elevated ferritin, cytopenias, coagulopathy, and/or splenomegaly or hepatomegaly. If not appropriately managed, MAS has a poor prognosis.
Dr. Alexei A. Grom, Professor and Research Director of Pediatrics at Cincinnati Children’s Hospital, says, “MAS associated with Still’s disease is a serious medical emergency, and is a hyperinflammatory response. There are limited options for treatment, and until very recently, treatment has depended on high-dose steroids with significant side effects. Now with the approval of Gamifant, a monoclonal antibody that targets this immune dysregulation directly, we can improve outcomes for children and adults.”
Gamifant is a monoclonal antibody that blocks interferon gamma (IFNγ), a molecule that is a cytokine involved in the inflammatory cascade associated with HLH and MAS. By blocking IFNγ, Gamifant directly interrupts the hyper-inflammatory state most effectively, addressing the disease process head-on rather than simply providing symptomatic treatment.
At present, Gamifant is the only FDA-approved treatment for primary HLH and now HLH/MAS with Still’s disease, confirming its strong place in the treatment of rare immune-mediated diseases. The utilization of Gamifant for HLH/MAS is to start with a single IV dose of 6 mg/kg on day 1, then 3mg/kg every 3 days until day 16, after which the patient would have the option to continue twice a week, or every 3rd day infusion into de-escalation and until the patient no longer needed treatment.
Sobi’s expanded use of Gamifant represents a significant step forward in addressing the serious unmet medical needs of patients experiencing life-threatening complications. As families and clinicians navigate the complex clinical landscape of MAS in Still’s disease, this immunotherapy could provide a ray of hope for improved survival and potentially improved quality of life.
Sobi is an international biotechnology company focused on rare diseases, committed to developing innovative therapies that improve patients’ lives in the context of hematology and immunology. With Gamifant’s expanded approval, Sobi will build on its mission to make meaningful differences for patients with limited treatment options.
References: Swedish Orphan Biovitrum AB. FDA approves Gamifant® (emapalumab-lzsg) as first-ever treatment for adults and children with macrophage activation syndrome in Still’s disease. PR Newswire. June 27, 2025. https://www.prnewswire.com/news-releases/fda-approves-gamifant-emapalumab-lzsg-as-first-ever-treatment-for-adults-and-children-with-macrophage-activation-syndrome-in-stills-disease-302493712.html
