• EPZ-5676 is a potent DOT1Linhibitor that causes tumor regressions in a rat xenograft model of MLL-rearranged leukemia.Rearrangements of the MLL gene define a genetically distinct subset of acute leukemias with poor prognosis. Current treatment options are of limited effectiveness; thus, there is a pressing need for new therapies for this disease. Genetic and small molecule inhibitor studies have demonstrated that the histone methyltransferase DOT1L is required for the development and maintenance of MLL-rearranged leukemia in model systems. Here we describe the characterization of EPZ-5676, a potent and selective aminonucleoside inhibitor of DOT1L histone methyltransferase activity. The compound has an inhibition constant value of 80 pM, and demonstrates 37 000-fold selectivity over all other methyltransferases tested. In cellular studies, EPZ-5676 inhibited H3K79 methylation and MLL-fusion target gene expression and demonstrated potent cell killing that was selective for acute leukemia lines bearing MLL translocations. Continuous IV infusion of EPZ-5676 in a rat xenograft model of MLL-rearranged leukemia caused complete tumor regressions that were sustained well beyond the compound infusion period with no significant weight loss or signs of toxicity. EPZ-5676 is therefore a potential treatment of MLL-rearranged leukemia and is under clinical investigation. (Blood. 2013;122(6):1017-1025 Introduction Rearrangements in the MLL gene at position 11q23 occur in 5% to 10% of acute leukemias of lymphoid, myeloid, or mixed/ indeterminant lineage and are especially common in infant acute leukemias and in secondary acute myeloid leukemias arising in patients following treatment of other malignancies with topoisomerase II inhibitors. [1][2][3][4] Acute leukemias bearing MLL rearrangements are aggressive diseases. Current treatment options are limited to chemotherapy and allogeneic hematopoietic stem cell transplantation; however, these have significant side effects and outcomes remain poor. As a result, there is intense interest in developing novel therapeutic strategies for this disease. The MLL gene encodes a large multidomain protein (MLL) that regulates transcription of developmental genes including the HOX genes. 1 The amino terminal portion of the protein contains regions that target MLL to DNA directly, whereas the carboxyl terminal portion of the protein contains a Su(Var)3-9, Enhancer of zeste and Trithorax domain with methyltransferase activity specific for lysine 4 of histone H3 (H3K4).5-9 MLL rearrangements result in the loss of the carboxyterminal methyltransferase domain and an in-frame fusion of the amino-terminal region of MLL to 1 of more than 60 potential fusion partners. [1][2][3] The vast majority of translocations result in oncogenic fusion proteins in which the native methyltransferase domain is replaced by sequences derived from AF4, AF9, AF10, and ENL, which interact with DOT1L directly or indirectly in complexes that promote transcriptional elongation.10-18 DOT1L is a histone methyltransferase enz...

Protein arginine methyltransferase-5 (PRMT5) is reported to have a role in diverse cellular processes, including tumorigenesis, and its overexpression is observed in cell lines and primary patient samples derived from lymphomas, particularly mantle cell lymphoma (MCL). Here we describe the identification and characterization of a potent and selective inhibitor of PRMT5 with antiproliferative effects in both in vitro and in vivo models of MCL. EPZ015666 (GSK3235025) is an orally available inhibitor of PRMT5 enzymatic activity in biochemical assays with a half-maximal inhibitory concentration (IC50) of 22 nM and broad selectivity against a panel of other histone methyltransferases. Treatment of MCL cell lines with EPZ015666 led to inhibition of SmD3 methylation and cell death, with IC50 values in the nanomolar range. Oral dosing with EPZ015666 demonstrated dose-dependent antitumor activity in multiple MCL xenograft models. EPZ015666 represents a validated chemical probe for further study of PRMT5 biology and arginine methylation in cancer and other diseases.

Mutations within the catalytic domain of the histone methyltransferase EZH2 have been identified in subsets of patients with non-Hodgkin lymphoma (NHL). These genetic alterations are hypothesized to confer an oncogenic dependency on EZH2 enzymatic activity in these cancers. We have previously reported the discovery of EPZ005678 and EPZ-6438, potent and selective S-adenosyl-methionine-competitive small molecule inhibitors of EZH2. Although both compounds are similar with respect to their mechanism of action and selectivity, EPZ-6438 possesses superior potency and drug-like properties, including good oral bioavailability in animals. Here, we characterize the activity of EPZ-6438 in preclinical models of NHL. EPZ-6438 selectively inhibits intracellular lysine 27 of histone H3 (H3K27) methylation in a concentration-and time-dependent manner in both EZH2 wild-type and mutant lymphoma cells. Inhibition of H3K27 trimethylation (H3K27Me3) leads to selective cell killing of human lymphoma cell lines bearing EZH2 catalytic domain point mutations. Treatment of EZH2-mutant NHL xenograft-bearing mice with EPZ-6438 causes dose-dependent tumor growth inhibition, including complete and sustained tumor regressions with correlative diminution of H3K27Me3 levels in tumors and selected normal tissues. Mice dosed orally with EPZ-6438 for 28 days remained tumor free for up to 63 days after stopping compound treatment in two EZH2-mutant xenograft models. These data confirm the dependency of EZH2-mutant NHL on EZH2 activity and portend the utility of EPZ-6438 as a potential treatment for these genetically defined cancers. Mol Cancer Ther; 13(4); 842-54. Ó2014 AACR.

ABSTRACT:We present herein a compilation and trend analysis of human i.v. pharmacokinetic data on 670 drugs representing, to our knowledge, the largest publicly available set of human clinical pharmacokinetic data. This data set provides the drug metabolism scientist with a robust and accurate resource suitable for a number of applications, including in silico modeling, in vitro-in vivo scaling, and physiologically based pharmacokinetic approaches. Clearance, volume of distribution at steady state, mean residence time, and terminal phase half-life were obtained or derived from original references exclusively from studies utilizing i.v. administration. Plasma protein binding data were collected from other sources to supplement these pharmacokinetic data. These parameters were analyzed concurrently with a range of simple physicochemical descriptors, and resultant trends and patterns within the data are presented. Our findings with this much expanded data set were consistent with earlier described notions of trends between physicochemical properties and pharmacokinetic behavior. These observations and analyses, along with the large database of human pharmacokinetic data, should enable future efforts aimed toward developing quantitative structure-pharmacokinetic relationships and improving our understanding of the relationship between fundamental chemical characteristics and drug disposition.The prediction of human pharmacokinetics for new compounds has become an important process in drug research. Previous reports have focused on prediction methods that utilize animal pharmacokinetic data (Caldwell et al

Pinometostat (EPZ-5676) is a first-in-class small-molecule inhibitor of the histone methyltransferase disrupter of telomeric silencing 1-like (DOT1L). In this phase 1 study, pinometostat was evaluated for safety and efficacy in adult patients with advanced acute leukemias, particularly those involving mixed lineage leukemia () gene rearrangements () resulting from 11q23 translocations. Fifty-one patients were enrolled into 6 dose-escalation cohorts (n = 26) and 2 expansion cohorts (n = 25) at pinometostat doses of 54 and 90 mg/m per day by continuous intravenous infusion in 28-day cycles. Because a maximum tolerated dose was not established in the dose-escalation phase, the expansion doses were selected based on safety and clinical response data combined with pharmacodynamic evidence of reduction in H3K79 methylation during dose escalation. Across all dose levels, plasma pinometostat concentrations increased in an approximately dose-proportional fashion, reaching an apparent steady-state by 4-8 hours after infusion, and rapidly decreased following treatment cessation. The most common adverse events, of any cause, were fatigue (39%), nausea (39%), constipation (35%), and febrile neutropenia (35%). Overall, 2 patients, both with t(11;19), experienced complete remission at 54 mg/m per day by continuous intravenous infusion, demonstrating proof of concept for delivering clinically meaningful responses through targeting DOT1L using the single agent pinometostat in leukemia patients. Administration of pinometostat was generally safe, with the maximum tolerated dose not being reached, although efficacy as a single agent was modest. This study demonstrates the therapeutic potential for targeting DOT1L in leukemia and lays the groundwork for future combination approaches in this patient population. This clinical trial is registered at www.clinicaltrials.gov as NCT01684150.

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We present here a novel integrative metabonomic approach to probe toxic effects of drugs in experimental animals using alpha-naphthylisothiocyanate (ANIT) as a model hepatotoxicant. Male Han-Wistar rats were dosed with ANIT (150 mg/kg, n = 25), and plasma and liver samples were collected for NMR and magic-angle spinning (MAS) NMR spectroscopy at 3, 7, 24, 31, and 168 h postdosing. Urine was collected continuously for 3 days prior to dosing and up to 168 h postdose. Histopathology and plasma clinical chemistry was also performed at all time points. Liver samples were analyzed either intact by 600 MHz 1H MAS NMR techniques or using high resolution (liquid state) 1H NMR of water-acetonitrile extracts. These data were related to sequential 1H NMR measurements in urine and plasma using pattern recognition methods. 1D 1H NMR spectra were data-reduced and analyzed using principal components analysis (PCA) to show the time-dependent biochemical variations induced by ANIT toxicity. From the eigenvector loadings of the PCA, those regions of the 1H NMR spectra and hence the combinations of endogenous metabolites marking the main phase of the toxic episode were identified. The ANIT-induced biochemical manifestations included a hepatic lipidosis associated with hyperlipidaemia; hyperglycaemia and glycosuria; increased urinary excretion of taurine and creatine; a shift in energy metabolism characterized by increased plasma ketone bodies with reduced urinary excretion of tricarboxylic acid cycle intermediates and raised hepatic bile acids leading to bile aciduria. The integration of metabolic data derived from several sources gives a holistic approach to the study of time-related toxic effects in the intact system and enables the characterization of key metabolic effects during the development and recovery from a toxic lesion.