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.

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BI 224436 is an HIV-1 integrase inhibitor with effective antiviral activity that acts through a mechanism that is distinct from that of integrase strand transfer inhibitors (INSTIs). This 3-quinolineacetic acid derivative series was identified using an enzymatic integrase long terminal repeat (LTR) DNA 3=-processing assay. A combination of medicinal chemistry, parallel synthesis, and structure-guided drug design led to the identification of BI 224436 as a candidate for preclinical profiling. It has antiviral 50% effective concentrations (

CARM1 is an arginine methyltransferase with diverse histone and non-histone substrates implicated in the regulation of cellular processes including transcriptional co-activation and RNA processing. CARM1 overexpression has been reported in multiple cancer types and has been shown to modulate oncogenic pathways in in vitro studies. Detailed understanding of the mechanism of action of CARM1 in oncogenesis has been limited by a lack of selective tool compounds, particularly for in vivo studies. We describe the identification and characterization of, to our knowledge, the first potent and selective inhibitor of CARM1 that exhibits anti-proliferative effects both in vitro and in vivo and, to our knowledge, the first demonstration of a role for CARM1 in multiple myeloma (MM). EZM2302 (GSK3359088) is an inhibitor of CARM1 enzymatic activity in biochemical assays (IC50 = 6 nM) with broad selectivity against other histone methyltransferases. Treatment of MM cell lines with EZM2302 leads to inhibition of PABP1 and SMB methylation and cell stasis with IC50 values in the nanomolar range. Oral dosing of EZM2302 demonstrates dose-dependent in vivo CARM1 inhibition and anti-tumor activity in an MM xenograft model. EZM2302 is a validated chemical probe suitable for further understanding the biological role CARM1 plays in cancer and other diseases.

ABSTRACT:The recent publication of a potent and selective inhibitor of protein methyltransferase 5 (PRMT5) provides the scientific community with in vivo-active tool compound EPZ015666 (GSK3235025) to probe the underlying pharmacology of this key enzyme. Herein, we report the design and optimization strategies employed on an initial hit compound with poor in vitro clearance to yield in vivo tool compound EPZ015666 and an additional potent in vitro tool molecule EPZ015866 (GSK3203591). KEYWORDS:Methyltransferase, PRMT5, property based optimization, structure guided design T he mammalian protein arginine methyltransferases are a group of nine enzymes that perform N G -mono methylation-, asymmetric-, or symmetric dimethylation of arginine residues on a range of nuclear and cytoplasmic protein substrates.1 One member of this group, PRMT5, is capable of performing methylation of up to two methyl groups and is currently believed to be the predominant enzyme for symmetric dimethylation. PRMT5 may play an important role in tumorigenesis and is upregulated in several human malignancies.2−8 The mechanism behind the cell-transforming capabilities of PRMT5 has been postulated to have roles in cell death, cell-cycle progression and cell growth, and proliferation and is still under investigation.9 Whether PRMT5 drives tumorigenesis by direct signal transduction, regulating gene expression, or by some other mechanism is generally unknown, although recent studies highlight a dependency on PRMT5 as part of the spliceosomal machinery with Sm proteins, particularly for MYC-driven tumors. 10EPZ015666 has recently been characterized as a potent inhibitor and in vivo tool compound of PRMT5.11 This compound is the first inhibitor to be described with a well characterized correlation between inhibition of PRMT5 enzyme and reduction of known substrate products including symmetric-dimethylated SmD3, coupled with a corresponding effect on tumor growth inhibition. In addition, structural biology studies highlighted a unique cation−π binding mode involving the tetrahydroisoquinoline (THIQ) containing chemical series as exemplified in the EPZ015666:PRMT5:-MEP50 cocrystal complex (PDB Codes: 4X60, 4X61). Herein we describe the medicinal chemistry optimization (Figure 1) in the development of tool compound EPZ015666.Compound 1 was recently described 11 as a hit identified from a 370 K member diversity high throughput screening (HTS) campaign, with modest inhibitory activity against PRMT5. Scheme 1 shows the synthetic route employed for the optimization of 1, as it enabled identification of SAR around the THIQ group at the penultimate step. Retaining the cyclopentylamino motif, a range of amines were used to open epoxide intermediate 5, providing the amino alcohol derivatives shown after boc-deprotection. No increase in activity was observed from this set, however, in comparison with the original hit compound (Scheme 1B). The contribution of the THIQ mediated cation−π interaction is apparent from this early data set with a number of non-THIQ co...