A Study to Evaluate the Efficacy, Safety and Pharmacokinetics of Emapalumab in Adult Patients With HLH

Inclusion Criteria: * Male and female patients of age 18 and older at the time of HLH diagnosis * Fulfilment of 5 of the 8 HLH-2004 clinical criteria * Patients diagnosed with malignancy-associated HLH must be treatment naïve; patients diagnosed with HLH driven by any other etiology or idiopathic can be either treatment naïve or treatment experienced * Patients with non-malignancy-associated or idiopathic HLH who have already received conventional therapy for HLH must have failed prior treatment as per the treating physician's judgement * Informed consent signed by the patient or by the patient's legally authorized representative(s) (as required by local law) * Willing to use highly effective methods of contraception from study drug initiation to 6 months after the last dose of study drug, if female and of childbearing potential. Exclusion Criteria: * Primary HLH * Current or scheduled administration of therapies known to trigger the cytokine release syndrome (e.g. chimeric antigen receptor (CAR)-modified T cells, bispecific T cell-engaging antibodies) * Current or scheduled administration of PD-1/PD-L1/CTLA-4 inhibitors * Life-expectancy associated with the underlying disease (triggering HLH) \< 3 months * Ongoing participation in an investigational trial, or administration of any investigational treatment within 30 days * History of hypersensitivity or allergy to any components of emapalumab * Active mycobacteria, Histoplasma capsulatum, or Leishmania infections * Eviden…