Abstract 2912: CRISPR-Cas9: A tool for rapid target discovery and validation

Genetic perturbations mediated by CRISPR-Cas9 are transforming the drug discovery process. In the hunt for novel drug targets, researchers finally have a screening tool with sufficient penetrance and power to identify new interactions, followed by a rapid gene editing technology to streamline validation approaches. At Horizon Discovery, we have now initiated more than 250 CRISPR-Cas9 knockout (KO) screens, including a significant effort to identify novel synthetic lethal interactions in colon and lung cancer genotypes. These screens have identified a reassuring number of known essential interactions, such as MDM2 and PPMID in TP53 wild type cancer cell lines. These results provide confidence in the ability of these screens to also discover novel targets that should make it through the validation process. Indeed, we have discovered novel targets for selective ablation of TP53 mutant colon cancers, several of which are strongly supported by the literature. In FBXW7 mutant colon cancers, CRISPR-Cas9 KO screens identified a set of potential novel druggable targets in addition to MCL1 - a known substrate of FBXW7, which showed a strong dependency in FBXW7 mutant lines. An important step in triaging primary hits ahead of extensive validation work has been secondary screens that target functional domains with high density sgRNA tiling. They allow more targets to be examined than would be feasible by any arrayed approach. Data from such screens, which test tens to hundreds of guides in unison, not only increases hit calling power, but can also yield information regarding important domains and mechanism of action. This was evident in the FBXW7 secondary screen data, where guides targeting the key functional BH domains of MCL1 proved to be the most effective. This information can be used to prioritise individual targets for further validation, using techniques that include an inducible CRISPR-Cas9 system to assess the effect of individual guides in an arrayed format on cell proliferation and survival, and CRISPRi. These data exemplify how CRISPR-Cas9 can enable the discovery of a new, more robust generation of drug and antibody targets. Citation Format: Ceri M. Wiggins, David Walter, Paul Russell, Clare Sheridan, Chantelle Hudson, Joanne Yarker, Carlos le Sage, Nicola McCarthy, Jonathan D. Moore. CRISPR-Cas9: A tool for rapid target discovery and validation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2912.