Abstract 346: Potential role for R191, potent and selective IRAK4 kinase inhibitor, in treatment of hematologic malignancies

Proceedings: AACR 107th Annual Meeting 2016; April 16-20, 2016; New Orleans, LA Recent advances in genome sequencing and tumor proteome and transcriptome analysis uncovered a key role for MyD88-dependent Toll-Like Receptor (TLR) and Interleukin-1 Receptor (IL-1R)-mediated signaling pathways in multiple hematologic malignancies. A third of activated B-cell-like diffuse large B-cell lymphoma (ABC DLBCL) and nearly 100% of Waldenstrom macroglobulinemia (WD) patients carry an activating Myd88 L265P mutation. Overexpression of multiple TLR pathway components, associated with deregulation of innate immune system and subsequent induction of proinflammatory bone marrow environment, are prominent features of myelodysplastic syndrome (MDS) and acute myelogenous leukemia (AML). IRAK4 kinase is a crucial enzyme in all MyD88-dependent signaling pathways, potentially making it an ideal target for disease modification with small molecule inhibitors. Through cell-based screening, we identified a potent small molecule IRAK1/4 kinase inhibitor, R191. R191 blocks TLR- and IL-1R-induced cytokine production in primary cells with potencies below 50nM while sparing unrelated pathways with at least 20-fold window. R191 is extremely potent in vitro against IRAK4 kinase (3 nM), yet exhibits good selectivity against a broad panel of kinases. In vivo, it decreases serum IL-6 in an acute mouse model of IL-1β-induced cytokine release and blocks joint inflammation in the collagen-induce arthritis model. R191 exhibited strong synergy with Bcl2 and BCR pathway inhibitors against a number of DLBCL lines in vitro. In multiple AML lines, R191 potently inhibited expression of PD-L1, potentially promoting recognition of AML blasts by the immune system. Based on the potential critical role of IRAK kinases in MDS, AML and Myd88 L265P lymphomas, R191 could provide a novel therapeutic modality in the management of multiple inflammation-driven hematologic malignancies. Citation Format: Vadim V. Markovtsov, Chrystelle Lamagna, Meagan Chan, Sothy Yi, Chi Young, Roy Frances, Stacey Siu, Sylvia Braselmann, Hui Li, Rajinder Singh, Gary Park, Esteban Masuda, Vanessa Taylor, Donald G. Payan. Potential role for R191, potent and selective IRAK4 kinase inhibitor, in treatment of hematologic malignancies. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 346.