Abstract ND09: M3913 induces the maladaptive unfolded protein response through a novel mechanism resulting in strong anti-tumor activity

Abstract Therapeutic strategies based on exacerbated stress signaling may represent novel and effective treatment paradigms in oncology. Here, we disclose for the first time the endoplasmic reticulum (ER) stress modulator (ERSM) M3913 that was discovered and developed following a phenotypic screening campaign. Mechanistically, M3913 engages an ER transmembrane protein not yet implicated in cancer biology to induce a Ca2+ shift from the ER towards the cytoplasm, resulting in an unfolded protein response and subsequent antitumor activity in sensitive preclinical models. We detected concurrent elevation of bona fide ER stress markers by several methods including qRT-PCR, Western Blotting analysis, and unbiased transcriptome analysis. Genetic removal of M3913’s putative ER transmembrane target abrogated the M3913-mediated, but not the Thapsigargin-mediated, ER stress response. PK/PD studies confirmed a dose- and time-dependent upregulation of ER stress markers in preclinical cancer models in vivo. As a monotherapy, M3913 induced full and partial tumor regression in preclinical models of multiple myeloma, non-small-cell lung cancer, triple-negative breast cancer, and other cancers. An in vitro combination screen indicated combination potential of M3913 with standard-of-care agents and novel candidate drugs. IND-enabling toxicology and additional mechanism-of-action studies in rat and minipig uncovered specific target organs for M3913 in line with expression of the target in human tissues. This presentation details mechanistic profiling data from M3913, reveals its putative ER-resident target and discusses forward translation studies that support M3913 as a novel therapeutic option for hard-to-treat subtypes of a variety of cancers. Citation Format: Frank Czauderna, Richard Schneider, Shivapriya Ramaswamy, Susanne Brandstetter, Elise Drouin, Olga Bogatyrova, Johanna Mazur, Qing Sun, Catherine Jorand-Lebrun, Eva Sherbetjian, Jonny Nachtigall, Carolyn Wing, Christian Hildebrand, Peter Ellinghaus, Isabelle Lemoine, Mac Johnson, Russell Hoover, Michael Clark, Ralph Lindemann. M3913 induces the maladaptive unfolded protein response through a novel mechanism resulting in strong anti-tumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr ND09.