Discovery of CTx-0391034 a novel potent and selective inhibitor of PRMT5 — ASN Events
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  3. Discovery of CTx-0391034 a novel potent and selective inhibitor of PRMT5

Discovery of CTx-0391034 a novel potent and selective inhibitor of PRMT5 (#151)

Ian Street 1 , Hendrik Falk 1 , Ylva E. Bergman 1 , Scott Walker 1 , Stefan E Sonderegger 1 , Elizabeth Allan 1 , Jonathan Baell 1 , Michelle A Camerino 1 , Loretta Cerruti 1 , Susan Charman 1 , Melanie de Silva 1 , Mark Devlin 1 , Olan Dolezal 1 , Richard Foitzik 1 , Danny Ganame 1 , Julian Grusovin 1 , Stefan Hermans 1 , Catherine Hemley 1 , Ian Holmes 1 , Wilhelmus Kersten 1 , Rachel Lagiakos 1 , Romina Lessene 1 , Kym Lowes 1 , Gill Lunniss 1 , Ben Morrow 1 , Anthony Natoli 1 , Michael Parker 1 , Tom Peat 1 , Jo-Anne Pinson 1 , Pat Pilling 1 , Sukhdeep Spall 1 , Alex Stupple 1 , Yan Tan 1 , Alison Thistlethwaite 1 , Emma Toulmin 1 , Karen White 1 , David Curtis 1 , Stephen Jane 1 , Brendon Monahan 1 , Paul Stupple 1
  1. Cancer Therapeutics CRC, Bundoora, VIC, Australia

Increased expression or dysregulation of protein arginine methyltransferase 5 (PRMT5) activity is associated with poor prognosis in many cancers. The aberrant activity of PRMT5 has been associated with pro-tumourigenic cellular changes including, increased protein synthesis, dysregulation of cell cycle, cellular adaptation to hypoxia, and suppression of normal cell death pathways.

We screened a library of 350,000 lead-like compounds with a biochemical assay measuring the methylation of a histone H4 peptide by the recombinant human PRMT5/MEP50 complex. Biochemical and biophysical profiling of the inhibitory compounds indicated that distinct binding modes were exhibited by different chemicals. Inhibitors displayed competitive, noncompetitive or uncompetitive interactions with respect to S-adenosyl methionine and the peptide substrate. Medicinal chemistry developed several classes of potent, highly selective inhibitors of PRMT5 methyltransferase activity from the hit set. The optimised tool compound, CTx-034, is a potent inhibitor of PRMT5 methyl transferase activity (KD = 2 nM), which is highly selective (>100-fold) versus a panel of 18 methyltransferases (including 6 PRMT family members), 11 lysine demethylases, and 15 safety related targets (GPCRs, ion channels, enzymes). Treatment of cancer cell lines with CTx-034 reduces cellular levels of symmetrically dimethylated H4 Arginine 3 (H4R3me2s), in a dose dependent manner (IC50=4 nM). Furthermore, within this chemical series the ability of compounds to reduce cellular levels of H4R3me2s closely correlates with PRMT5 inhibitory activity supporting PRMT5 as the cellular target of these compounds, and suggesting that PRMT5 is the major writer of this histone mark in many cancer cell lines. CTx-034 also inhibits the cellular sDMR of other PRMT5histone and non-histone substrates. Conversely, CTx-034 treatment does not reduce levels of H4R3 asymmetric dimethylation, a histone mark catalysed by PRMT1.

Finally, CTx-034 has good oral bioavailability and pharmacokinetic properties making it an excellent tool compound for cellular and in vivo proof of concept studies.