Abstract 4702: Combination of BET inhibitor INCB054329 and LSD1 inhibitor INCB059872 is synergistic for the treatment of AML in vitro and in vivo

Proceedings: AACR 107th Annual Meeting 2016; April 16-20, 2016; New Orleans, LA Acute myeloid leukemia (AML) is a disease characterized by the expansion of a hematopoietic stem cell like population caused in part by a block of myeloid differentiation. In AML an altered epigenetic landscape, often arising from genetic lesions in epigenetic regulators, enforces an oncogenic expression profile and suppresses myeloid differentiation. Indeed, a screen for essential genes in the murine MLL-AF9 retroviral model of leukemia identified the epigenetic regulators BRD4 and LSD1 as potential therapeutic targets. Furthermore, independent studies have demonstrated that inhibition of BRD4 or LSD1 by small molecules induced myeloid differentiation and suppressed leukemic stem cell phenotype in AML models. Recently it has been demonstrated that combinations of inhibitors that target distinct epigenetic regulators can exhibit synergistic effects on target gene transcription and cancer cell growth. Therefore we investigated the potential combinatorial effects of a novel FAD-directed LSD1 inhibitor, INCB059872, together with the BET inhibitor, INCB054329. The effects of single agent LSD1 and BET inhibitors or their combination were assessed using human AML models in vitro and in vivo. INCB054329 as monotherapy inhibited cell proliferation and induced apoptosis in human AML cell lines, while INCB059872 induced cellular differentiation in these cell lines as determined by the induction of myeloid differentiation markers, CD86 and CD11b. The combination of INCB054329 and INCB059872 enhanced myeloid differentiation and apoptosis in human AML cell lines compared with the single agents. Interestingly, c-myc expression was down-regulated to greater extent with the combination of both compounds compared to either agent alone. Enhanced anti-tumor efficacy with favorable tolerability was observed in human AML xenograft models when both agents were administered simultaneously or sequentially, with INCB059872 dosing regimens preceding INCB054329 administration demonstrating the greatest efficacy. These ongoing studies demonstrate that concurrent inhibition of two distinct families of epigenetic regulators, BET and LSD1, is active in preclinical AML models, and provide a rationale for the clinical evaluation of this novel, epigenetic doublet therapy in AML. Citation Format: Xuesong Liu, Matthew Stubbs, Min Ye, Roberts Collins, Margaret Favata, Gengjie Yang, Melody Diamond, Valerie Dostalik, Yvonne Lo, Chunhong He, Liangxing Wu, Andrew Combs, Wenqing Yao, Gregory Hollis, Reid Huber, Peggy Scherle, Bruce Ruggeri, Phillip Liu, Sang Hyun Lee. Combination of BET inhibitor INCB054329 and LSD1 inhibitor INCB059872 is synergistic for the treatment of AML in vitro and in vivo . [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 4702.