Abstract 1883: Large scale viability screening with PRISM underscores non-inhibitory properties of small molecules

Abstract

Abstract Oncology drug discovery has been dependent on phenotypic screening that lead to discovery of many drugs that remain essential cancer treatments to this day. Historically, logistical and technological limitations have hampered the scale of phenotypic small molecule screening across genomic diverse models. Until recently, large scale phenotypic screening across many cell lines, reflecting the somatic diversity in cancer, has not been possible. The PRISM technology does allow for a high-throughput approach to phenotypic viability screening by pooling cell lines and deconvoluting their response to small molecules using unique integrated DNA-barcodes. Here, we report on the results of a large phenotypic screening effort to identify novel small molecules and targets that can expand our knowledge on cancer vulnerabilities and can spur development of phenotypic drug discovery. A library of 18.000 compounds was assembled based on structural diversity and ability to induce gene-expression changes. Of these 18.000 compounds, around 3.500 were found to reduce cell viability of at least 5 cell lines in the PRISM assay. Of the cytotoxic compounds, we did not identify many small molecules that correlated strongly with CRISPR KO dependency data from project Achilles, and instead found that gene-expression correlations hold much more predictive value. By using additional approaches, we were able to identify the target of select novel cytotoxic small molecules and their respective mechanism-of-action. To our surprise, we have identified few compounds that act as canonical inhibitors of cancer drivers, and instead found compounds that act as molecular glues, prodrugs or inhibitors of more general cellular processes. These findings make a strong case for large scale phenotypic viability screening across genomically diverse models as a complementary approach to target identification next to target based drug discovery. Citation Format: Lucian de Waal, Kevin Larpenteur, Li Wang, Cong Zhu, Jordan Bryan, Mustafa Kocak, Corrie Aghia, Joshua Bittker, Victor Jones, Anita Vrcic, Edward McBride, Samantha Bender, Kalea Gore, Frank Li, Zhenghao Chen, Aviad Tsherniak, Aravind Subramanian, Daphne Koller, Jeffery Settleman, Chris C. Mader, David Stokoe, Ari Firestone, Jennifer A. Roth, Todd R. Golub. Large scale viability screening with PRISM underscores non-inhibitory properties of small molecules [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1883.