Discovery of Novel Indazoles as Potent and Selective PI3Kδ Inhibitors with High Efficacy for Treatment of Hepatocellular Carcinoma

PI3K delta inhibitors have been developed for treatment of B-cell malignancies and inflammatory and autoimmune diseases. However, their therapeutic role in solid tumors like hepatocellular carcinoma (HCC) is rarely reported. Thus, the development of potent and selective PI3K delta inhibitors with a new chemotype and therapy is highly desirable. Through the scaffold-hopping strategy, indazole was first described as the core structure of propeller-shaped PI3K delta inhibitors. A total of 26 indazole derivatives were designed and prepared to identify a novel compound 9x with good isoform selectivity, PK profile, and potency. Compared to Idelalisib and Sorafenib, the pharmacodynamic (PD) studies showed that 9x exhibits superior efficacy in HCC cell lines and xenograft models, and the mechanistic study showed that 9x robustly suppresses the downstream AKT pathway to induce subsequent apoptotic cell death in HCC models. Therefore, this work provides a new structural design of PI3K delta inhibitors for a novel and efficient therapeutic small molecule toward HCC.