Combined therapy with DR5- targeting antibody-drug conjugate and CDK inhibitors as a novel strategy for advanced MSS and MSI-H colorectal cancer

Targeted therapies for advanced microsatellite stable (MSS) subtypes of colorectal cancer (CRC) continue to present significant clinical challenges. Death receptor 5 (DR5/TRAIL-R2) is an apoptotic receptor frequently overexpressed in various cancers. Evidence suggests that DR5-targeting antibody drug conjugates (ADC) show promising efficacy in several cancers. In this study, we demonstrated DR5 as a clinically significant target for CRC by analyzing tissue microarrays from advanced CRC cohorts (473 MSS cases and 36 MSI-H cases), as well as data from a TCGA cohort comprising 418 cases. Our novel clinical-stage DR5-targeting ADC, Oba01, designed to deliver the microtubule-disrupting agent MMAE, shows superior therapeutic efficacy across various CRC cell lines, patient-derived xenografts (PDXs), and corresponding organoids (PDXOs), regardless of their MSS or MSI-H status. Importantly, our functional RNAseq and proteomic analysis of the impact of Oba01 on global gene expression revealed that the cell cycle pathway and cyclin-dependent kinases (CDKs) are mechanistically synergistic targets of the drug's effects. Supporting this idea, we presented solid evidence to show Oba01 and abemaciclib, a FDA-approved CDK4/6 inhibitor for metastatic breast cancer, substantially synergize across various clinically relevant models derived from advanced CRC patients with both MSS and MSI-H status, in both in vitro and in vivo settings. The fact that this synergy spans multiple CDK inhibitors further highlights the potential of combining DR5-mediated delivery of MMAE with CDK inhibition as a novel therapeutic strategy for advanced CRC patients, especially those with the challenging to treat MSS subtype.