Dysregulation of lysine (K)-specific demethylase 1A (LSD1), also known as KDM1A, has been implicated in the development of various cancers, including leukemia. Here, we describe the antileukemic activity and mechanism of action of T-3775440, a novel irreversible LSD1 inhibitor. Cell growth analysis of leukemia cell lines revealed that acute erythroid leukemia (AEL) and acute megakaryoblastic leukemia cells (AMKL) were highly sensitive to this compound. T-3775440 treatment enforced transdifferentiation of erythroid/megakaryocytic lineages into granulomonocytic-like lineage cells. Mechanistically, T-3775440 disrupted the interaction between LSD1 and growth factor-independent 1B (GFI1B), a transcription factor critical for the differentiation processes of erythroid and megakaryocytic lineage cells. Knockdown of LSD1 and GFI1B recapitulated T-3775440-induced transdifferentiation and cell growth suppression, highlighting the significance of LSD1-GFI1B axis inhibition with regard to the anti-AML effects of T-3775440. Moreover, T-3775440 exhibited significant antitumor efficacy in AEL and AMKL xenograft models. Our findings provide a rationale for evaluating LSD1 inhibitors as potential treatments and indicate a novel mechanism of action against AML, particularly AEL and AMKL. Mol Cancer Ther; 16(2); 273-84. ©2016 AACR.

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The development of low μM inhibitors of the Mycobacterium tuberculosis phosphatase PtpA is reported. The most potent of these inhibitors (K i = 1.4 ± 0.3 μM) was found to be selective when tested against a panel of human tyrosine and dual-specificity phosphatases (11-fold vs the highly homologous HCPtpA, and >70-fold vs all others tested). Modeling the inhibitor-PtpA complexes explained the structure-activity relationships observed in vitro and revealed further possibilities for compound development. KeywordsMycobacterium tuberculosis; Phosphatase; Inhibitor; PtpA Tuberculosis (TB) is a chronic infectious disease caused by Mycobacterium tuberculosis (Mtb). Out of over 13 million active cases each year, TB causes nearly 2 million deaths. 1 Current treatment of drug-sensitive strains requires 6-9 months to fully eradicate the infection. New Mtb drugs that act on novel targets are needed to shorten treatment and address the emergence of antibiotic resistance.Mtb encodes two protein tyrosine phosphatases (PTPs), PtpA and PtpB, that are promising new targets for TB drug development. 2 These PTPs are secreted by Mtb 3 into the cytosol of infected macrophages, obviating the need for inhibitors to enter bacterial cells. 4 Although genetic deletion of PtpA or PtpB does not affect Mtb growth in culture, 4,5 these deletions severely attenuate growth in sensitive infected macrophages. 4 These data suggest that the Mtb PTPs act on macrophage signaling pathways to promote Mtb survival in the infected host. Although not classical drug targets because they are not essential in vitro, targeting the secreted PTPs in the host macrophage circumvents two central resistance mechanisms of Mtb; that is, poor drug permeability due to the Mtb cell wall, 6 and pump-mediated drug efflux. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptWe previously reported the development of low-molecular weight inhibitors of PtpB 8 using a substrate-based, fragment identification and optimization approach termed Substrate Activity Screening (SAS). 9 Here, we applied the same method to PtpA to prepare and evaluate a library of inhibitors selective for Mtb PtpA. These studies identified low-micromolar PtpA inhibitors with selectivity versus a panel of human phosphatases. Modeling our compounds bound in the active site of PtpA explained the observed structure-activity relationships (SAR) and highlighted further possibilities for compound development.A library of O-aryl phosphate substrate fragments was previously developed to target PtpB. 8 Using this library, we identified compounds for further optimization towards PtpA. Due to the ease of synthetic diversification of aryl difluoromethylphosphonic acid (DFMP) inhibitors, we varied DFMP analogs to establish SAR for PtpA inhibition. Although DFMP inhibitors have traditionally exhibited poor cell permeability due to the dianionic nature of this pharmacophore, DFMP inhibitors of the human phosphatase PTP1B, an enzyme involved in insulin signaling, have rece...

We incorporated various polar groups into previously described piperidine-4-carboxamide CCR5 antagonists to improve their metabolic stability in human hepatic microsomes. Introducing a carbamoyl group into the phenyl ring of the 4-benzylpiperidine moiety afforded the less lipophilic compound 5f, which possessed both high metabolic stability and good inhibitory activity of HIV-1 envelope-mediated membrane fusion (IC(50) = 5.8 nM). Further optimization to increase potency led to the discovery of 1-acetyl-N-{3-[4-(4-carbamoylbenzyl)piperidin-1-yl]propyl}-N-(3-chloro-4-methylphenyl)piperidine-4-carboxamide (5m, TAK-220), which showed high CCR5 binding affinity (IC(50) = 3.5 nM) and potent inhibition of membrane fusion (IC(50) = 0.42 nM), as well as good metabolic stability. Compound 5m strongly inhibited the replication of CCR5-using HIV-1 clinical isolates in human peripheral blood mononuclear cells (mean EC(50) = 1.1 nM, EC(90) = 13 nM) and exhibited a good pharmacokinetic profile in monkeys (BA = 29%). This compound has been chosen as a clinical candidate for further development.