Novel and Highly Potent ATR Inhibitor M4344 Kills Cancer Cells With Replication Stress, and Enhances the Chemotherapeutic Activity of Widely Used DNA Damaging Agents

Abstract

Although several ATR inhibitors are in development, there are unresolved questions regarding their differential potency, molecular signatures of cancer patients for predicting activity and most effective therapeutic combinations. Here, we elucidate how to improve ATR-based chemotherapy with the newly developed ATR inhibitor, M4344 using in vitro and in vivo models. The potency of M4344 was compared with the clinically developed ATR inhibitors BAY1895344, berzosertib, and ceralasertib. The anticancer activity of M4344 was investigated as monotherapy and combination with clinical DNA damaging agents in multiple cancer cell lines, patient-derived tumor organoids and mouse xenograft models. We also elucidated the anticancer mechanisms and potential biomarkers for M4344. We demonstrate that M4344 is highly potent among the clinically developed ATR inhibitors. Replication stress (RepStress) and neuroendocrine (NE) gene expression signatures are significantly associated with a response to M4344 treatment. M4344 kills cancer cells by inducing cellular catastrophe and DNA damage. M4344 is highly synergistic with a broad range of DNA-targeting anticancer agents. It significantly synergizes with topotecan and irinotecan in patient-derived tumor organoids and xenograft models. Taken together, M4344 is a promising and highly potent ATR inhibitor. It enhances the activity of clinical DNA damaging agents commonly used in cancer treatment including topoisomerase inhibitors, gemcitabine, cisplatin and talazoparib. RepStress and NE gene expression signatures can be exploited as predictive markers for M4344.

Precision Oncology with Drugs Targeting the Replication Stress, ATR, and Schlafen 11

“…Enhancing replicative damage by blunting the RepStress response pathways with ATR inhibitors is discussed below [8,[63][64][65][66][67]. Synthetic lethality for the PARP inhibitors and platinum derivatives in HRD cancers is being applied for cancer treatment [68,69] and recent studies in animal models suggest such synthetic lethality for TOP1 inhibitors [10,58].…”

“…The RepStress gene signature is a weighted expression signature encompassing 18 genes-SRSF1, SUV39H1, GINS1, PRPS1, KPNA2, AURKB, TNPO2, ORC6, CCNA2, LIG3, MTF2, GADD45G, POLA1, POLD4, POLE4, RFC5, RMI1, RRM1-derived by leveraging established cellular characteristics that portend high RepStress including amplification of MYC and its paralogs (MYCN and MYCL), expression of phosphorylated CHK1 (p-CHK1), and sensitivity to the CHK1 and WEE1 cell cycle checkpoint inhibitors [100]. The RepStress gene signature was recently validated as a response predictor for ATR inhibitors across a set of 14 cell lines from different tissues of origin [64]. Figure 4 also shows its predictive value also for topotecan and gemcitabine in the Broad Institute database.…”

“…Three ATR inhibitors are in advanced clinical development: Berzosertib (M6620, alias VX-970), Ceralasertib (AZD6738), and Elimusertib (BAY1895344) [8,[65][66][67]108]. Additional drugs are in early development comprising M4344 and M1774 (EMD-Serono Merck, Darmstadt, Germany), ART0380 (Artios Pharma, New York, NY, USA) and RP-3500 (Repare Therapeutics, Quebec, QC, Canada) [64]. Currently, over 30 clinical trials are ongoing with ATR inhibitors alone or in combination with DNA damaging agents including nucleoside analogues, platinumbased agents, TOP and PARP inhibitors [5,6,63,64,66,[109][110][111].…”

“…Additional drugs are in early development comprising M4344 and M1774 (EMD-Serono Merck, Darmstadt, Germany), ART0380 (Artios Pharma, New York, NY, USA) and RP-3500 (Repare Therapeutics, Quebec, QC, Canada) [64]. Currently, over 30 clinical trials are ongoing with ATR inhibitors alone or in combination with DNA damaging agents including nucleoside analogues, platinumbased agents, TOP and PARP inhibitors [5,6,63,64,66,[109][110][111]. Broadly, these clinical trials aim to exploit: (i) the synthetic lethal interactions of the ATR-CHK1 pathway with the overexpression of oncogenes (RAS, APOBEC3A, and c-MYC), deficiency of ATM and ARID1A (AT-rich interaction domain 1A) and SLFN11 [6,63,65,85,92] using ATR inhibitor monotherapy or (ii) the dependence of high RepStress tumors on ATR, generally in combination with RepStress-inducing agents (described in Sections 3.4 and 3.5).…”

“…First, how do the ATR inhibitors differ from each other. Our recent preclinical studies showed a broad range of potency among the ATR inhibitors with M4344 being the most potent followed by Elimusertib (BAY1895344), Berzosertib (M6620), and Ceralasertib (AZD6738) [64]. Elimusertib and Ceralasertib are given orally while Berzosertib is given intravenously.…”