bioPROTACs establish RAS as a degradable target and provide novel RAS biology insights

Abstract

Mutations to RAS proteins (H-, N-, and K-RAS) are amongst the most common oncogenic drivers and tumors harboring these lesions are some of the most difficult to treat. Although the recently discovered covalent small molecules against the KRAS G12C mutant have shown promising efficacy against lung cancers, traditional barriers remain for drugging the more prevalent KRAS G12D and KRAS G12V mutants. Targeted degradation has emerged as an attractive alternative approach but for KRAS, identification of the required high-affinity ligands continues to be a challenge. Another significant hurdle is the discovery of a hybrid molecule that appends an E3 ligase-recruiting moiety in a manner that satisfies the precise geometries required for productive polyubiquitin transfer while maintaining favorable druglike properties. As a tool to gain insights into the advantages and feasibility of KRAS targeted-degradation, we applied the bioPROTAC approach. This workflow centers on the intracellular expression of a chimeric protein consisting of a high-affinity target-binding domain fused to an engineered E3 ligase adapter. We generated a series of anti-RAS bioPROTACs that span different RAS isoform/nucleotide-state specificities and leverage different E3 ligases. Overall, our results provide definitive evidence for the degradability of RAS proteins. We further elucidate the functional consequences of RAS degradation, the susceptibility and degradation kinetics of various mutant KRAS, and the prevalence of different nucleotide-states in WT and mutant KRAS. Finally, if delivery challenges can be addressed, anti-RAS bioPROTACs will be exciting candidates for clinical development.

Targeted degradation of PCNA outperforms stoichiometric inhibition to result in programed cell death

“…A central advantage of biodegraders is their relatively facile discovery as they can be constructed with small-biologic POI binders that can either pre-exist or be identified with a variety of methods such as yeast- and phage-display technologies. Indeed, this has allowed us to engineer a variety of active biodegraders to GFP-fusion proteins 12 , RAS 20,22 , and PCNA 12 .…”