Identification of dual-targeting PROTACs for ataxia telangiectasia and RAD3-related and aurora kinase A as chemo-sensitizers for leukemia cells.

The ataxia telangiectasia and RAD3-related (ATR) kinase is a central regulator of DNA damage responses. Its pharmacological degradation by proteolysis-targeting chimeras (PROTACs) represents a promising strategy to sensitize cancer cells to DNA-damaging chemotherapy. It is currently unknown if ATR PROTACs can be pharmacologically designed to target a second cancer-relevant kinase. In this study, we report the design, synthesis, and biological evaluation of novel cereblon (CRBN)-based PROTACs for ATR. Structure-guided design and chemical synthesis enabled the development of a focused library of degraders based on selective ATR inhibitors and optimized CRBN ligands. Among the synthesized compounds, Abd141 turns out as the most promising degrader, showing potent ATR degradation in human leukemia cells, without affecting ATM, WEE1 or DNA-PKcs. Consistently, the developed PROTACs prove activity in an in vitro ATR/ATRIP binding assay. Abd141 exhibits high chemical, microsomal, and plasma stability, and no cytotoxicity in non-cancerous HEK293 cells. Proteomic studies and immunoblot experiments identify aurora kinase A (AURKA) as additional target of CRBN-induced proteasomal degradation by Abd141. Dose-degradation studies of Abd141 in the MOLT-4 cell line yielded a DC50 of 97.7 nM for ATR and 6.7 nM for AURKA. These findings disclose Abd141 as effective dual ATR/AURKA degrader and innovative chemo-sensitizer that encourages preclinical development.