The U.S. Food and Drug Administration has accepted Sobi's supplemental Biologics License Application (sBLA) for Gamifant® (emapalumab-lzsg), granting it Priority Review status for treating hemophagocytic lymphohistiocytosis (HLH)/macrophage activation syndrome (MAS) in Still's disease. The regulatory decision is expected by June 27, 2025.
Clinical Need and Disease Impact
HLH/MAS represents a severe hyperinflammatory complication predominantly affecting patients with Still's disease, including both systemic juvenile idiopathic arthritis (sJIA) and adult-onset Still's disease (AOSD). The condition manifests through persistent high fever, elevated ferritin levels, blood cell abnormalities, coagulation disorders, and enlarged liver and spleen. Without proper treatment, patients may face life-threatening complications including multiple organ failure.
"HLH/MAS in Still's disease is a serious and potentially fatal complication where patients can experience intense hyperinflammation and even multiple organ failure," explains Dr. Lydia Abad-Franch, Head of R&D and Chief Medical Officer at Sobi. "There is no approved therapy for HLH/MAS today."
Promising Clinical Trial Results
The sBLA submission is supported by pooled data from two clinical studies - EMERALD (NCT05001737) and NI-0501-06 (NCT03311854) - involving 39 patients. The trials yielded encouraging results:
- 53% of patients achieved complete response by Week 8
- 85% of patients demonstrated complete response at some point during the studies
- Glucocorticoid doses were reduced by 70.1% after just two weeks of treatment
Therapeutic Mechanism and Current Approval Status
Gamifant functions as a monoclonal antibody that specifically targets and neutralizes interferon gamma (IFN-γ), a key driver of hyperinflammation. The drug received FDA approval in 2018 for treating primary HLH in both adult and pediatric patients who show refractory, recurrent, or progressive disease, or intolerance to conventional HLH therapy.
Dr. Abad-Franch notes that if approved for this new indication, Gamifant may help reduce the need for high-dose glucocorticoids in HLH/MAS patients, offering a potentially crucial treatment option for this serious condition.
Treatment Administration
When used in its currently approved indication, Gamifant is administered through intravenous infusion over one hour, twice weekly, until patients undergo hematopoietic stem cell transplantation (HSCT). This established administration protocol provides a framework for its potential use in HLH/MAS patients, should the sBLA receive approval.
