IDO Inhibitor Development Shows Fresh Signs of Life Across Tumor Types

Figure. The Role of IDO1 in the Tumor Microenvironment¹⁷ (Click to Enlarge)

Leveraging an Essential Amino Acid

Tryptophan is the rarest of the essential amino acids—those that must be acquired through the diet—and, as such, its metabolism is tightly regulated.¹³ Several biochemical pathways are involved in tryptophan breakdown, but the kynurenine (KYN) pathway predominates, converting tryptophan into biologically active metabolites, including the eponymous KYN.^13-17