Selective and Potent PROTAC Degraders of c-Src Kinase

Abstract

Using dasatinib linked to E3 ligase ligands, we identified a potent and selective dual Csk/c-Src PROTAC degrader. We then replaced dasatinib, the c-Src-directed ligand, with a conformationselective analogue that stabilizes the αC-helix-out conformation of c-Src. Using the αC-helix-out ligand, we identified a PROTAC that is potent and selective for c-Src. We demonstrated a high degree of catalysis with our c-Src PROTACs. Using our c-Src PROTACs, we identified pharmacological advantages of c-Src degradation compared to inhibition with respect to cancer cell proliferation.

Discovery of a Covalent Inhibitor Selectively Targeting the Autophosphorylation Site of c-Src Kinase

“…This differentiation sets it apart from kinase inhibitors that occupy the ATP pocket and extend into the P-loop for enhanced selectivity. , Intriguingly, although ( R )-LW-Srci-8 effectively inhibited c-Src signaling in cells at low micromolar concentrations, a much higher concentration was required for its anticancer effects (Figure D–F). Such discrepancy may coincide with previous studies indicating loss of c-Src enzymatic activities failed to recapitulate the potent antiproliferation effect induced by c-Src knockdown, implying the key role of its nonenzymatic functions in sustaining cancer cell growth. , Indeed, a recently reported PROTAC degrader of c-Src demonstrated considerably improved antiproliferation effects compared with its enzymatic inhibitors . Therefore, the selective covalent c-Src inhibitor developed from the current study, along with the protein degraders, may serve as a valuable chemical toolkit in precisely defining the enzymatic versus nonenzymatic roles of c-Src in both physiological and pathological contexts …”

“…Such discrepancy may coincide with previous studies indicating loss of c-Src enzymatic activities failed to recapitulate the potent antiproliferation effect induced by c-Src knockdown, implying the key role of its nonenzymatic functions in sustaining cancer cell growth. , Indeed, a recently reported PROTAC degrader of c-Src demonstrated considerably improved antiproliferation effects compared with its enzymatic inhibitors . Therefore, the selective covalent c-Src inhibitor developed from the current study, along with the protein degraders, may serve as a valuable chemical toolkit in precisely defining the enzymatic versus nonenzymatic roles of c-Src in both physiological and pathological contexts …”