Biopharmaceutical company Swedish Orphan Biovitrum AB (Sobi) (STO:SOBI) announced on Thursday that the US Food and Drug Administration (FDA) has accepted its supplemental Biologics License Application (sBLA) for Gamifant (emapalumab-lzsg) for treating hemophagocytic lymphohistiocytosis/macrophage activation syndrome (HLH/MAS) in Still's disease patients who have not responded to glucocorticoids or have recurrent MAS.

The FDA granted Priority Review, setting a Prescription Drug User Fee Act (PDUFA) target date of 27 June 2025.

HLH/MAS is a severe inflammatory complication linked to systemic juvenile idiopathic arthritis and adult-onset Still's disease, often presenting with high fever, cytopenias and hepatosplenomegaly. The sBLA is supported by pooled data from two clinical trials, EMERALD and NI-0501-06, which enrolled a total of 39 patients.

Results showed that 53% of patients achieved a complete response by Week 8, and 85% responded at some point during treatment. Additionally, glucocorticoid doses were reduced by 70.1% after two weeks.

Gamifant, a monoclonal antibody that neutralizes interferon gamma, was originally approved by the FDA in 2018 for primary HLH in patients with refractory, recurrent or progressive disease.