Novel Oxindole Sulfonamides and Sulfamides: EPZ031686, the First Orally Bioavailable Small Molecule SMYD3 Inhibitor

Abstract

SMYD3 has been implicated in a range of cancers; however, until now no potent selective small molecule inhibitors have been available for target validation studies. A novel oxindole series of SMYD3 inhibitors was identified through screening of the Epizyme proprietary histone methyltransferase-biased library. Potency optimization afforded two tool compounds, sulfonamide EPZ031686 and sulfamide EPZ030456, with cellular potency at a level sufficient to probe the in vitro biology of SMYD3 inhibition. EPZ031686 shows good bioavailability following oral dosing in mice making it a suitable tool for potential in vivo target validation studies. KEYWORDS: SMYD3, oxindole, methyltransferase, KMT, oncology, tool compound S et and Mynd Domain containing 3 (SMYD3) is a lysine methyltransferase (KMT) expressed at high levels in a number of different cancer histologies and is associated with a poor clinical prognosis. 1−10 While no single mechanism has emerged to explain this correlation, a number of studies have implicated SMYD3 in the regulation of gene transcription and signal transduction pathways critical for cell survival in breast, liver, prostate, pancreatic, and lung cancer models. 4,7−9 In addition, considerable evidence has been reported in the literature showing that genetic knockdown of SMYD3 leads to a decrease in proliferation of a variety of cancer cell lines. 4,[7][8][9]11 Two studies, employing RNAi-based technologies, have shown that ablation of SMYD3 in hepatocellular carcinoma cell lines greatly reduces cell viability and that its pro-oncogenic role is dependent on its catalytic activity. 7,9 Moreover, SMYD3 has also been shown to be a critical mediator of transformation induced by a KRAS gain-of-function mutation in both pancreatic and lung adenocarcinoma mouse models; these models were likewise dependent on the catalytic activity of SMYD3. 11 The biological function of SMYD3 is still poorly understood. Early studies of SMYD3 suggested that its primary function is to methylate histones. Indeed, several reports have indicated that SMYD3 modifies histone H3 on lysine 4, 9,12 but have also identified a novel modification of histone H4 on lysine 5. 7 The results of these studies have not yet yielded a clear picture of how SMYD3 might be regulating chromatin, but a recent study has strongly implicated SMYD3 as a direct regulator of MAPK pathways in the cytoplasm and not as a regulator of transcription. MAP3K2 (MEKK2) was shown to be trimethylated at lysine 260 by SMYD3. Modification of this residue leads to enhanced downstream MAPK activation and appears to be critical for mutant KRAS driven oncogenesis. 11 SMYD3's role in cancer cell line proliferation, its effect on known oncogenic signal transduction pathways, and the association of SMYD3 mRNA expression with aggressive transformed phenotypes make SMYD3 an attractive target for therapeutic intervention. We report here the first potent and selective small molecule inhibitors suitable for target validation studies.Compound 1 was identified as a mi...

SMYD3: An Oncogenic Driver Targeting Epigenetic Regulation and Signaling Pathways

“…EPZ031686 is a noncompetitive inhibitor for SAM and the MAP3K2 substrate, while EPZ030456 showed mixed type inhibition with respect to SAM, and noncompetitive inhibition with respect to MAP3K2. EPZ031686 also displayed good bioavailability in mice, making it a suitable compound for in vivo studies [95].…”

Methyltransferase Inhibitors: Competing with, or Exploiting the Bound Cofactor

“…For example, the cocrystal structure of the substrate-competitive, SAM-uncompetitive SMYD2 inhibitor AZ505 in complex with SMYD2 and SAM, showed that the ketone oxygen of the benzooxazinone moiety is 2.8 Å away from the sulfonium methyl group, which can act as a hydrogen-bond donor [47,85]. Stabilizing amide-sulfonium interactions have also been reported for other SMYD-family inhibitors such as EPZ030456 and an AZ505-analog called A-893 [86,87].…”

Recent Advances in Chemical Tools for the Regulation and Study of Protein Lysine Methyltransferases

“…The SMYD (SET and MYND domain‐containing) family proteins are also histone methyltransferases, and one of them, SMYD3, is H3 K4 methyltransferase. EPZ031686 was reported as an inhibitor of SMYD3 . SMYD2 was reported to methylate H3 K4 and H3 K36 as well as other substrates, such as tumor suppressor proteins p53 and Rb (retinoblastoma protein) .…”