Real-world use of emapalumab in hemophagocytic lymphohistiocytosis: a scoping review of published evidence.

Background: Emapalumab, an interferon-γ (interferon-gamma)-blocking monoclonal antibody, has emerged as a targeted therapy for refractory hemophagocytic lymphohistiocytosis (HLH). This scoping review summarizes real-world evidence of its clinical use across HLH subtypes. Methods: A comprehensive search of PubMed, Scopus, and Web of Science through September 2025 identified studies reporting emapalumab use outside clinical trials. Case reports, series, and observational studies describing clinical outcomes were included. Results: Thirty-one publications comprising 86 patients were analyzed. Disease contexts included familial/genetic HLH (n = 11), rheumatology-associated macrophage activation syndrome (MAS; n = 12), malignancy-associated HLH (n = 25), infection-associated HLH (n = 22), CAR-T/IEC-HS or cytokine-release-syndrome-related HLH (chimeric antigen receptor T-cell/immune effector cell-associated hemophagocytic syndrome; n = 11), and other secondary HLH (n = 5). Across all categories, emapalumab achieved rapid suppression of hyperinflammation, typically within 1-2 weeks. Clinical response rates were 100% in familial HLH, 91.7% in rheumatology-associated MAS, 72.7% in infection-associated HLH, 90.9% in CAR-T/IEC-HS-related HLH, and 80% in other secondary HLH. In contrast, only 6 of 25 patients with malignancy-associated HLH (24%) showed partial or complete responses, reflecting inferior outcomes due to underlying disease progression. Overall survival was highest in familial and infection-associated subgroups. The reported adverse events were generally infrequent and mild in the published cases, but causality cannot be reliably established given the complexity of the underlying disease and concurrent therapies. Conclusion: Real-world evidence demonstrates that emapalumab induces rapid and durable disease control across diverse HLH subtypes, with a favorable tolerability profile. However, outcomes remain markedly inferior in malignancy-associated HLH, where response rates are limited to approximately 24%, primarily due to the impact of underlying malignancy. Its role as rescue or bridging therapy to hematopoietic stem-cell transplantation (HSCT) is increasingly supported in both pediatric and adult populations.