Targeted inhibition of Bruton's Tyrosine Kinase (BTK) with ibrutinib and other agents has become important treatment options in chronic lymphocytic leukemia, Waldenström's Macroglobulinemia, Mantle cell lymphoma, and non-GCB DLBCL. Clinical trials combining small molecule inhibitors with monoclonal antibodies have been initiated at rapid pace, with the biological understanding between their synergistic interactions lagging behind. Here, we have evaluated the synergy between BTK inhibitors and monoclonal antibody therapy via macrophage mediated antibody dependent cellular phagocytosis (ADCP). Initially, we observed increased ADCP with ibrutinib, whilst second generation BTK inhibitors failed to synergistically interact with monoclonal antibody treatment. Kinase activity profiling under BTK inhibition identified significant loss of Janus Kinase 2 (JAK2) only under ibrutinib treatment. We validated this potential off-target effect via JAK inhibition in vitro as well as with CRISPR/Cas9 JAK2-/- experiments in vivo, showing increased ADCP and prolonged survival, respectively. This data supports inhibition of the JAK-STAT (Signal Transducers and Activators of Transcription) signaling pathway in B-cell malignancies in combination with monoclonal antibody therapy to increase macrophage-mediated immune responses.
Keywords: ADCP; B-cell lymphoma; Ibrutinib; JAK; macrophage; phagocytosis; ruxolitinib; therapeutic antibody.