Abstract 3365: Transcriptomics-based stratification of response to MAPK inhibition in vitro better predicts sensitivity to single agent and combination treatment than MAPK genomic alteration status alone
Authors: Brothwood Jessica , Biondo Andrea , Dao Kim-Hien , Hearn Keisha , Hindley Chris , Kandola Navrohit , Keer Harold , Lyons John , Nakatsuru Yoko , O'Reilly Marc , Wallis Nicola , Saini Harpreet 
Published: June 2022

Abstract
Overactivation of mitogen-activated protein kinase (MAPK) signaling is a frequently observed driver of many cancers. Targeted MAPK pathway inhibitors have been approved as therapies in patient populations with genomic alterations to MAPK pathway genes (e.g. dabrafenib in BRAF-mutant melanoma), with multiple other MAPK-targeted therapies in development. We have previously demonstrated that cell lines with MAPK pathway genomic alterations show increased sensitivity to ASTX029, our potent and selective dual-mechanism ERK inhibitor which is currently undergoing clinical development. However, MAPK oncogene status alone is not a universal indicator of sensitivity, nor is it clear that genomic markers of sensitivity to single agent inhibition represent the optimal approach to predicting response to MAPK targeted agents in the combination setting (e.g. sotorasib + trametinib). We therefore analysed MAPK pathway related transcriptional signatures to assess predictability for response to ASTX029 in combination with a SHP2 inhibitor.
We previously presented data from large-scale viability screens assessing the response to ASTX029 as a single agent treatment (437 cell lines), as well as in combination with an inhibitor of SHP2 (491 cell lines), an upstream adaptor protein in the MAPK pathway. Using these data, several published transcriptional signatures related to the MAPK pathway were assessed for their ability to stratify sensitive vs resistant cell lines when benchmarked against MAPK oncogene genomic status alone.
All assessed transcriptomics-based scores had a significant positive correlation with growth inhibition for ERK inhibitor single agent treatment as well as in combination with a SHP2 inhibitor. Transcriptomics-based scores were shown to be more sensitive than the use of mutant MAPK oncogene status alone based on assessment of binomial regression models. The significant increase in sensitivity enables the identification of additional cell lines responsive to MAPK pathway inhibition. The sensitivity was further increased when considering response to the combination of an ERK and SHP2 inhibitor compared to the ERK inhibitor as a single agent.
This analysis demonstrates the potential use of MAPK pathway-related transcriptomics-based scores for the stratification of MAPK pathway inhibitor response. ASTX029 is currently undergoing clinical development in advanced solid tumours (NCT03520075) and transcriptomics-based methods may provide utility in refining patient selection in the clinic for single agent or combination approaches.
Citation Format: Jessica Brothwood, Andrea Biondo, Kim-Hien Dao, Keisha Hearn, Chris Hindley, Navrohit Kandola, Harold Keer, John Lyons, Yoko Nakatsuru, Marc O'Reilly, Nicola Wallis, Harpreet Saini. Transcriptomics-based stratification of response to MAPK inhibition in vitro better predicts sensitivity to single agent and combination treatment than MAPK genomic alteration status alone [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 3365.