Marine natural products and other derivatives as potent indoleamine 2,3-dioxygenase inhibitors.

Cancer cells are able to elaborate enzymatic mechanisms allowing tumors to resist or escape imune rejection. Among the enzymes involved, indoleamine 2,3-dioxygenase (IDO), an intracellular enzyme that initiates the first and rate-limiting step of tryptophan breakdown along the kynurenine pathway, has emerged as a promising molecular target for the development of new immunotherapeutic anticancer agents. This review summarizes the synthesis and IDO activities of the different classes of marine and other inhibitors reported so far.