Synthesis and Anti-Tumor Evaluation of Carboranyl BMS-202 Analogues—A Case of Carborane Not as Phenyl Ring Mimetic

Carborane is considered a three-dimensional mimetic of phenyl rings in medicinal chemistry. BMS-202 is a potent PD-L1 inhibitor that can block the PD-L1/PD-1 interaction and restore the immune response to cancer cells. Herein, we replaced the terminal phenyl group of BMS-202 with carborane and prepared its carboranyl BMS-202 analogues. The results showed a loss of PD-L1 binding affinity due to the bulky size of carborane, suggesting that carborane cannot serve as a phenyl ring mimetic in certain cases. Docking study demonstrated that the narrow binding pocket of PD-L1 could not hold the bulky carborane, resulting in loss of its activity. Compounds 1a and 1b exhibited anti-proliferative activities on a broad scope of cancer cell lines. Further studies indicate that compound 1a can induce cell apoptosis and lead to G1 cell cycle phase arrest. The boron biodistribution study of compound 1a revealed that the brain/blood uptake ratio was 0.60 ± 0.08, exhibiting a good blood-brain penetration capability.