Adjunctive ruxolitinib attenuates inflammation and enhances antiparasitic immunity in human volunteers experimentally infected with Plasmodium falciparum

Inhibiting the host inflammatory response to malaria represents a potential strategy to improve clinical outcomes and inhibit immunoregulatory pathways that underlie suboptimal development of antiparasitic immunity. Ruxolitinib is a JAK 1/2 inhibitor that reduces inflammatory biomarkers when used in myeloproliferative disorders, and inhibits type-1 interferons and enhances CD4+ T cell immunity when combined with anti-parasitic drugs in animal models. Here we report the results of a double-blind randomised placebo-controlled trial evaluating the ability of ruxolitinib to reduce inflammatory responses and boost anti-parasitic immunity in malaria-naive volunteers inoculated with blood-stage Plasmodium falciparum. Twenty participants were inoculated, and randomized on day 8 to receive artemether-lumefantrine with either ruxolitinib or placebo. Ninety days later, participants who remained eligible were re-inoculated with a second infection. Ruxolitinib was safe and well-tolerated, and attenuated the host inflammatory response to the initial infection, with reduced post-treatment increases in the inflammatory biomarker CRP, as well as markers of disease severity including angiopoietin-2 and ICAM-1. Further, ruxolitinib enhanced the immune memory response following a second inoculation, with increased plasma levels of HLA-DR and CXCL13, indicating enhanced immune activation and germinal centre responses, respectively. These data support the further evaluation of ruxolitinib as an adjunctive treatment to improve clinical outcomes and boost anti-parasitic immunity in clinical malaria.