Ruxolitinib as First Line Treatment in Primary Haemophagocytic Lymphohistiocytosis (R-HLH)

Haemophagocytic lymphohistiocytosis (HLH) is a devastating inflammatory condition caused by uncontrolled proliferation of activated lymphocytes and macrophages secreting an excess of inflammatory cytokines. Treatment of HLH aims at decreasing inflammation and requires also treatment of the underlying trigger, if any. The principal goal of the induction therapy is to suppress the life-threatening inflammatory process. Once remission of HLH achieved, patients require allogeneic haematopoietic stem cell transplantation (HSCT), the only curative therapy to date. Despite significant treatment progress, mortality remains high. The study aims to implement a targeted treatment that is less aggressive than conventional approaches (Etoposide / ATG / Alemtuzumab). A better understanding of the pathophysiology of primary HLH has opened new avenues for targeted therapy. The central cytokine of the HLH process is IFNγ. IFNγ as well as most cytokines that are elevated in HLH, signal via Janus Kinase (JAK) and Signal Transducer and Activator of Transcription (STAT)-associated receptors. Ruxolitinib, a selective JAK1/2 inhibitor has shown its efficacy in mouse models of HLH, where it significantly reduced disease manifestations and enhanced survival. Notably, Ruxolitinib diminished CD8+ T-cell accumulation and cytokine production, while sparing degranulation and cytotoxicity. Recently, Ruxolitinib has also been used successfully in humans in isolated cases of refractory primary and secondary HLH. This is a National, phase II, non-comparative and non-randomized, study in France with 9 participating centers. The chosen experimental plan is a Simon's Optimal 2-Step Design.