Abstract A169: Combination of TPC-144, a reversible LSD1 inhibitor, and a hypomethylating agent resulted in synergistic antitumor efficacy in preclinical models of AML

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Abstract Background: Lysine-specific demethylase 1A (LSD1/KDM1A) is a flavin adenine dinucleotide (FAD)-dependent histone demethylase that specifically modifies histone H3 lysine 4 and lysine 9. LSD1 activity is implicated in the pathogenesis of several human cancers, and recent studies indicated that the inhibition of LSD1 is a promising therapeutic strategy for acute myeloid leukemia (AML). Decitabine and azacitidine, FDA-approved agents for the treatment of AML and myelodysplastic syndrome, alter global DNA methylation by inhibiting DNA methyltransferases (DNMTs), resulting in apoptosis and differentiation. Since it is reported that LSD1 directly demethylates and stabilizes DNMT1 by protection from degradation, we hypothesized that an LSD1 inhibitor could augment anti-AML activity of DNMT inhibitors. Previously, we demonstrated that TPC-144, a novel reversible LSD1 inhibitor, was efficacious in preclinical models of AML. Here, we report the activity of TPC-144 in combination with decitabine in cell-based and in vivo studies. Material and Methods: In vitro studies on growth inhibition and apoptosis were conducted using AML cell lines by measuring cellular ATP content (Cell-Titer Glo, Promega) and sub-G1 population, respectively. For expression changes of surface markers, cells were stained with specific antibodies (BD Pharmingen) and analyzed by flow cytometry. mRNA levels of LSD1 target genes were quantitated by real-time PCR. LINE-1 methylation levels were evaluated in Global DNA Methylation-LINE-1 Kit (Active Motif). In vivo efficacy was evaluated in human AML xenograft models in SCID mice. TPC-144 and decitabine was administered orally or intraperitoneally, respectively. Results: The combination of TPC-144 and decitabine showed synergistic growth inhibition of human AML cells in vitro. TPC-144 enhanced apoptosis induction in combination with low-dose decitabine at the concentrations at which TPC-144 decreased DNMT1 protein levels and LINE-1 methylation levels. Combination treatment strongly increased expression of surface markers of differentiation such as CD86 and CD11b, compared with single-agent treatment. In AML xenograft models, the combination of TPC-144 and decitabine was tolerated without signs of hematopoietic toxicities, and demonstrated curative antitumor efficacy compared with each inhibitor alone in a decitabine-sensitive xenograft model. Importantly, the combination treatment of TPC-144 and decitabine exhibited strong antitumor efficacy even in a decitabine-insensitive AML model. Conclusions: TPC-144, a novel potent and selective reversible LSD1 inhibitor, demonstrated synergistic antitumor efficacy in combination with decitabine in human AML cell lines and xenograft models. This combination was well tolerated and showed strong efficacy not only in decitabine-sensitive but also in decitabine-insensitive AML models. Therefore, combination of TPC-144 and decitabine could enhance their therapeutic value for the treatment of AML patients. Citation Format: Akiko Osada, Aki Kawagishi, Ryo Hatanaka, Takumitsu Machida, Kenjiro Ito, Satoshi Yamashita, Takahiro Ogawa, Tadashi Imaoka, Kenichi Matsuo, Teruhiro Utsugi, Yoshikazu Iwasawa. Combination of TPC-144, a reversible LSD1 inhibitor, and a hypomethylating agent resulted in synergistic antitumor efficacy in preclinical models of AML [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A169.