DDRE-03. THERAPEUTIC TARGETING OF THE ERK AND CDK PATHWAYS IN PRECLINICAL MODELS OF BRAIN METASTASES

Abstract

Abstract Brain metastases (BM) are the most common neoplasm to affect the adult central nervous system. BM develop in 40-50% of advanced lung adenocarcinoma (LUAD), but the lack of durable response to chemotherapy, immunotherapy, or targeted therapy results in death within a year of BM diagnosis. Several advances have been made in identifying genetic drivers of primary cancers. The cell cycle, RAS and ERK pathways have all been implicated in as critical oncogenic regulators, with aberrations linked to driving the progression and metastasis of LUAD. Abemaciclib is a targeted CDK4/6 inhibitor, and LY3214996 is selective ERK1/2 inhibitor, and have shown efficacy in preclinical tumor models as well as in clinical trials. Furthermore, both therapeutics can interfere with the cell cycle, abemaciclib through targeting CDK4/6 and LY3214996 through cyclinD1. Here we present data assessing abemaciclib and LY3214996, as single and combined agents, in cell lines across different KRAS and CDKN2A mutational backgrounds. Seven days post-intracranial inoculation of NSCLC and NSCLC-BM line, mice received either abemaciclib, LY3214996, or a combination P.O. daily for 21 days, and were monitored pre- and post-treatment for tumor growth with bioluminescent imaging. In vitro we demonstrated a dose-dependent reduction in cell growth with each treatment, as well as cell arrest in G1 phase. In vivo, whereas cell lines with a combined KRAS mutation and CDKN2A mutation/deletion had no significant reduction in BM growth, cell lines with a CDKN2A del or BRAF mutation had significant BM reduction, with single agents and combined treatment. Further research is necessary to elucidate under what genetic contexts abemaciclib, LY3214996 or the combination are most effective. Nonetheless, this work highlights that abemaciclib and LY3214996 should be further explored for CDKN2A or BRAF mutant BM.