Clinical experience with emapalumab treatment in a group of children with primary hemophagocytic lymphohistiocytosis

Primary hemophagocytic lymphohistiocytosis (pHLH) is a group of genetically determined disorders characterized by severe and fulminant systemic inflammation, cytopenia, and multiple organ involvement. A dexamethasone-and-etoposide–based HLH-2004 protocol is widely used to treat pHLH, yet often fails to produce the disease control required for the next treatment step: hematopoietic stem cell transplantation (HSCT). We report on the use of the interferon gamma inhibitor emapalumab in seven children aged 6–39 months with pHLH. Three patients received emapalumab at an average starting dose of 1.7 mg/kg and had no active HLH by median day 28. Four patients received emapalumab at an average starting dose of 7.2 mg/kg and had no active HLH by median day 14 (P = 0,0015). We suggest that the higher starting dose of emapalumab, as well as its combination with Janus kinase inhibitors, might increase the remission rate in pHLH and the success of subsequent HSCT.