Real-World Treatment Patterns and Outcomes Among Patients with Secondary Hemophagocytic Lymphohistiocytosis Treated with Emapalumab in the United States: The Real-HLH Study

Background: Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening, hyperinflammatory syndrome caused by the overproduction of proinflammatory cytokines, such as interferon gamma (IFNγ). Secondary HLH (sHLH) occurs in the context of an underlying disease (malignancy, rheumatologic, or metabolic disease) and/or an infection. Emapalumab is a fully human anti-IFNγ monoclonal antibody approved by the FDA in 2018 for refractory, recurrent, or progressive primary HLH (pHLH), or intolerance with conventional therapy. Since its approval, there are limited data on emapalumab use in a real-world setting. The REAL-HLH study assessed real-world treatment patterns and outcomes among patients with HLH treated with emapalumab.