Optimization of a Screening Hit toward M2912, an Oral Tankyrase Inhibitor with Antitumor Activity in Colorectal Cancer Models

Abstract

Constitutive activation of the canonical Wnt signaling pathway, in most cases driven by inactivation of the tumor suppressor APC, is a hallmark of colorectal cancer. Tankyrases are druggable key regulators in these malignancies and are considered as attractive targets for therapeutic interventions, although no inhibitor has been progressed to clinical development yet. We continued our efforts to develop tankyrase inhibitors targeting the nicotinamide pocket with suitable drug-like properties for investigating effects of Wnt pathway inhibition on tumor growth. Herein, the identification of a screening hit series and its optimization through scaffold hopping and SAR exploration is described. The systematic assessment delivered M2912, a compound with an optimal balance between excellent TNKS potency, exquisite PARP selectivity, and a predicted human PK compatible with once daily oral dosing. Modulation of cellular Wnt pathway activity and significant tumor growth inhibition was demonstrated with this compound in colorectal xenograft models in vivo.

Small-Molecule Inhibitors of Tankyrases as Prospective Therapeutics for Cancer

“…136,137 Among the fragment hits thus generated were 2-(4methoxyphenyl)quinazolin-4(3H)-one ( 9) 136 and 6 7). 137 The former underwent two cycles of SAR investigation, with focus directed from branched substituents to azacyclic moieties at the C4′ position of the pendant phenyl. 136 Compound 11 was singled out for its well-balanced profile of drug-like properties including solubility, metabolic stability, potency, and selectivity (IC 50 s(TNKS1/TNKS2/PARP1/PARP2) = 0.007/0.009/ 0.782/ND μM) (Figure 7) and was the first quinazolin-4(3H)-one-based nicotinamide mimetic that demonstrated dose-dependent downregulation of the WNT/β-catenin pathway via inhibition of tankyrase activity in mouse xenografts derived from DLD-1 cells.…”

“…This scaffold hopping approach brought about 12 (M2912, previously known as MSC2504877, Figure 7), which displayed sub-nanomolar inhibitory activity against both tankyrases in ELISA assays (IC 50 s(TNKS1/TNKS2/PARP1/PARP2) = 0.0006/0.0009/0.928/ND μM 137 or earlier 0.0007/0.0008/ 0.540/ND μM 111 ) but was less potent in chemiluminescent assays performed at BPS Bioscience Inc. (IC 50 s(TNKS1/ TNKS2/PARP1/PARP2) = 0.0013/0.0014/0.14/0.20 μM). 137 The opposite was true for its potency toward PARP1 (vide supra). These variable data underscore that a comparison of IC 50 values should not be made unless they are acquired using identical assay conditions.…”

“…As expected, M2912 interacts with tankyrase 1 via hydrogen bonding to G1185 and S1221 and π−π stacking with Y1224 in their cocrystal structure (Figure 5D). 137 The 6-methyl group protrudes into a lipophilic cavity formed by three tyrosine residuesY1203, Y1213, and Y1224which was considered to be vital to the excellent biochemical and cellular potency of M2912. At the other end of the molecule, the 2-hydroxypropan-2-yl moiety lies at the exit of the nicotinamide-binding subsite, with the hydroxy group making no contacts with surrounding amino acids or water molecules.…”

“…A high-throughput in vitro screen, where a homogeneous biochemical assay using time-resolved fluorescence resonance energy transfer (FRET) technology was followed by an orthogonal, more sensitive enzyme-linked immunosorbent assay (ELISA), was deployed to funnel the Merck compound collection; both assays measured the physiological auto-PARylation activity of tankyrases. , Among the fragment hits thus generated were 2-(4-methoxyphenyl)­quinazolin-4­(3 H )-one ( 9 ) and 6-( p -tolyl)­imidazo­[1,2- a ]­pyrazin-8­(7 H )-one ( 10 ) (Figure ). The former underwent two cycles of SAR investigation, with focus directed from branched substituents to azacyclic moieties at the C4′ position of the pendant phenyl .…”

Adp-Ribosylation as Post-Translational Modification of Proteins: Use of Inhibitors in Cancer Control

“…In the first attempts to develop ART inhibitors, few chemical structures were shown to target PARPs and tankyrases: XAV939 is a promiscuous inhibitor of PARP1 and tankyrases, while PJ34 and UPF1069 are broad PARP/tankyrase inhibitors. In recent years, inhibitors were developed specifically for tankyrases: some of them bind to the nicotinamide subsite (NS) (such as XAV939, RK-582, LZZ-02, AZ1366), or to the adenosine subsite (AS) (IWR-1, OM-1700, OD366, G007-LK and K-756) [101][102][103][104][105][106][107][108][109][110]. Dual binders (DB), recognizing both nicotinamide and adenosine subsites, have been found among PARP1 inhibitors (olaparib): for TNKS, several inhibitors showed potential therapeutic use (CMP4, WIKI4, TNKS656) [31].…”