Abstract 4598: Discovery of novel MTA-cooperative PRMT5 inhibitors as targeted therapeutics for MTAP-deleted cancers

Abstract Homozygous deletions of the p16/CDKN2a (cyclin dependent kinase inhibitor 2A) locus, which is responsible for regulating the cell cycle, are commonly found in cancer and often involve the deletion of adjacent genes. One such adjacent gene is methylthioadenosine phosphorylase (MTAP), involved in metabolism, located on chromosome 9p21 in close proximity to the p16/CDKN2A tumor-suppressor locus. Co-deletion of MTAP is observed in approximately 80-90% of tumors with homozygous deletion of CDKN2A, representing 10-15% of all human tumors. These tumor types, including non-small cell lung cancer, pancreatic adenocarcinoma, glioblastoma, and mesothelioma, have a poor prognosis, highlighting the significant unmet medical need in this area. Deletion of MTAP leads to a significant accumulation of methylthioadenosine (MTA) in cells. MTA, at high concentrations, selectively inhibits the PRMT5 methyltransferase enzyme, competing with the substrate S-adenosylmethionine (SAM) required for methylation reactions. As a result, the overall level of symmetric arginine dimethylation throughout the proteome is reduced. This heightened sensitivity to modulation of methylosome activity makes cells with MTAP deletion more susceptible to therapeutic targeting of PRMT5. Hence, selective targeting of PRMT5 in cancers with homozygous MTAP deletion represents a promising strategy for specifically eliminating cancer cells with this genetic alteration. Ryvu has developed MTA-cooperative PRMT5 inhibitors characterized by good drug-like physicochemical properties and inhibition of methyltransferase activity with IC50 values in the low nanomolar range. A structure-based lead optimization delivered compounds coming from two independent series with high selective potency in MTAP-deleted cell lines and DMPK profiles allowing an oral administration. The antitumor activities were compared in vitro and in vivo to MRTX1719 and AMG193 in MTAP null tumors such as HCT116 MTAP KO, DoHH-2 and Lu99. The correlation between compound exposure and on-target effect was confirmed in PK/PD and efficacy studies. Taken together, these studies confirm that MTA cooperative PRMT5 inhibitors exert strong synthetic lethal phenotype in MTAP deleted cancers and offer an exciting therapeutic opportunity for a large patient population. Citation Format: Adam Radzimierski, Aneta Bobowska, Agata Stachowicz, Kamil Kuś, Kamila Kozłowska-Tomczyk, Agnieszka Ludwig-Słomczyńska, Paulina Podkalicka-Gołda, Aniela Gołas, Monika Żukowska, Pavlo Lebed, Przemysław Wyrębek, Daria Szukiel, Matylda Stefaniak, Oleksandr Popika, Julia Krzywik, Sujit Sasmal, Paulina Niedziejko-Ćwiertnia, Klara Korta-Piątek, Karolina Fijołkowska, Aleksandra Więckowska, Marta Olszak-Płachta, Swapnil Nipunge, Mateusz Świrski, Marek Wronowski, Henryk Pawlik, Quỳnh Vũ, Katarzyna Łagosz-Ćwik, Mateusz Stoszko, Szymon Woroszyło, Igor Tomczyk, Ewelina Gabor-Worwa, Nilesh Gaud, Anna Kowal-Chwast, Dawid Gogola, Magdalena Miodek, Róża Starczak, Agata Dudek, Jacek Faber, Bożena Winnik, Sanja Novak-Ratajczak, Agnieszka Świrska, Karolina Gluza, Paweł Guzik, Katarzyna Banaszak, Nicolas Boutard, Grzegorz Ćwiertnia, Krzysztof Brzózka, Mateusz Nowak, Anna Bartosik, Didier Pez. Discovery of novel MTA-cooperative PRMT5 inhibitors as targeted therapeutics for MTAP-deleted cancers abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4598.