Discovery of novel hydroxyamidine based indoleamine 2,3-dioxygenase 1 (IDO1) and thioredoxin reductase 1 (TrxR1) dual inhibitors.

In order to take advantage of both immunotherapeutic and metabolic antitumor agents, novel dual indoleamine 2,3- dioxygenase 1 (IDO1) and thioredoxin reductase 1 (TrxR1) inhibitors were designed. Thioredoxin reductase 1 (TrxR1) is a main ROS modulator within CRC cells. Indoleamine 2,3-dioxygenase (IDO1) is crucial controller for tryptophan (Trp) metabolism that is also important for CRC immunotherapy. Herein, ten compounds 12a-j containing hydroxyamidine scaffold were designed, synthesized and evaluated for inhibitory activities against IDO1/TrxR1 enzyme and CRC cells. Among these compounds, the most active compound 12d (ZC0109) showed excellent and balanced activity against both IDO1 (IC50 = 0.05 μM) and TrxR1 (IC50 = 3.00 ± 0.25 μM) were selected for further evaluation. Compound ZC0109 exhibited good dual inhibition against IDO1 and TrxR1 both in vitro and in vivo. Further mechanistic studies reveal that, through IDO1 and TrxR1 inhibition by ZC0109 treatment, accumulated ROS effectively induced apoptosis and G1/S cell cycle arrest in cancer cells. In vivo evaluation demonstrated excellent anti-tumor effect of ZC0109 with the notable ability of promoting ROS-induced apoptosis, reducing kynurenine level in plasma and restoring anti-tumor immune response. Thus, ZC0109 represents a potential CRC therapy agent for further development.