Design, Synthesis, and Evaluation of Phenylpyrrole Derivatives as Small-Molecule Activators of BAX.

Small-molecule BAX activators can trigger intrinsic apoptosis directly and thus hold unique potential as a new class of anticancer therapy. Current arsenal of known BAX activators is very limited. In this work, we first identified an active hit with micromolar binding affinity to BAX through virtual screening, and then replaced the complex hexahydrocyclopenta[c]quinoline moiety in its structure through scaffold hopping. Multiple rounds of structural optimization led us to finally focus on the compounds with a phenylpyrrole core moiety. The optimal compound (27c) exhibited selective binding to BAX with submicromolar binding affinity (IC50 = 300 nmol/L). Functional assays validated that 27c activated BAX in living cells and consequently induced intrinsic apoptosis. Cell viability tests indicated that 27c was effective not only against hematologic cancers but also drug-resistant solid tumors when combined with a BCL-XL inhibitor. Although the in vivo PK properties of 27c revealed certain limitations such as relatively short half-life and rapid clearance, its novel structural scaffold and compelling in vitro potency position it as a promising starting point for future development.