Discovery of SIAIS178 as an Effective BCR-ABL Degrader by Recruiting Von Hippel-Lindau (VHL) E3 Ubiquitin Ligase

The oncogenic fusion protein Bcr-Abl is the driving force of leukemogenesis in chronic myeloid leukemia (CML). Despite great progress for CML treatment through application of tyrosine kinase inhibitors (TKIs) against Bcr-Abl, long-term drug administration and clinical resistance continue to be an issue. Herein, we described the design, synthesis, and evaluation of novel proteolysis-targeting chimeric (PROTAC) small molecules targeting Bcr-Abl which connect dasatinib and VHL E3 ubiquitin Ligase ligand by extensive optimization of linkers. Our efforts have yielded SIAIS178 (19), which induces proper interaction between Bcr-Abl and VHL Ligase leading to effective degradation of Bcr-Abl protein, achieves significant growth inhibition of Bcr-Abl⁺ leukemic cells in vitro, and induces substantial tumor regression against K562 xenograft tumors in vivo. In addition, SIAIS178 also degrades several clinically relevant resistance-conferring mutations. Our data indicate that SIAIS178 as efficacious Bcr-Abl degrader warrants extensive further investigation for the treatment of Bcr-Abl⁺ leukemia.