Abstract 4712: Discovery of INCB059872, a novel FAD-directed LSD1 inhibitor that is effective in preclinical models of human and murine AML

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. Lysine specific demethylase 1 (LSD1) catalyzes the demethylation of lysine 4 and 9 of histone H3 through an FAD-dependent redox process. Aberrant LSD1 activity has been proposed to maintain oncogenic programs and prevent differentiation of multiple subtypes of AML. Here, we describe INCB059872, a potent, selective and orally bioavailable inhibitor of LSD1 that achieves inhibitory activity through the formation of covalent FAD-adducts. INCB059872 inhibited cellular proliferation and induced cellular differentiation as measured by induction of CD86 and CD11b myeloid differentiation markers in a panel of human AML cell lines and primary human AML cells ex vivo. In vivo, pharmacodynamic (PD) assays confirmed the sustained induction of CD86 in human AML xenograft models, consistent with the mechanism of FAD-directed inhibition of LSD1. Oral administration of INCB059872 significantly inhibited tumor growth of human AML xenograft models as a single agent at doses exhibiting significant PD effects in vivo. Efficacy was further evaluated in the murine retroviral MLL-AF9 disseminated leukemia model that recapitulates hallmarks of human AML. INCB059872 significantly prolonged the median survival of MLL-AF9 expressing leukemic mice compared with vehicle treated animals. Mechanistic studies demonstrated that INCB059872 induced cell differentiation of murine blast cells, reduced blast colonies, and normalized clinical hematological parameters to those of non-leukemic mice. Notably, in both human AML xenografts and the murine MLL-AF9 leukemic model, maximal efficacy could be achieved with both daily (QD) and alternative-day (QoD) dosing regimens of INCB059872, consistent with the prolonged PD effects observed. Collectively, these studies demonstrate the key role that LSD1 activity can play in preventing leukemic cell differentiation, and support the therapeutic potential of INCB059872 in the treatment of human AML. Citation Format: Sang Hyun Lee, Matthew Stubbs, Xuesong Mike Liu, Melody Diamond, Valerie Dostalik, Min Ye, Yvonne Lo, Margaret Favata, Gengjie Yang, Karen Gallagher, Lynn Leffet, Chunhong He, Liangxing Wu, Alexander Margulis, Maryanne Covington, Richard Wynn, Wenqing Yao, Gregory Hollis, Reid Huber, Bruce Ruggeri, Peggy Scherle. Discovery of INCB059872, a novel FAD-directed LSD1 inhibitor that is effective in preclinical models of human and murine AML. [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 4712.