Discovery of Hydroxyamidine Derivatives as Highly Potent, Selective Indoleamine-2,3-dioxygenase 1 Inhibitors.

In this study, a series of novel hydroxyamidine derivatives were identified as potent and selective IDO1 inhibitors by structure-based drug design. Among them, compounds 13-15 and 18 exhibited favorable enzymatic and cellular activities. Compound 18 showed improved bioavailability in mouse, rat, and dog (F% = 44%, 58.8%, 102.1%, respectively). With reasonable in vivo pharmacokinetic properties, compound 18 was further evaluated in a transgenic MC38 xenograft mouse model. The combination of compound 18 with PD-1 monoclonal antibody showed a synergistic antitumor effect. These data indicated that compound 18 as a potential cancer immunotherapy agent should warrant further investigation.