IDO, also referred to indoleamine 2,3-dioxygenase, is an enzyme that plays a role in suppressing the immune system through catalyzing the oxidative cleavage of Tryptophan because T cells undergoing antigen-dependent activation require tryptophan for cell proliferation and survival. IDO inhibitors may help to promote an enhanced immune response against the tumor by blocking the IDO enzyme which reduces the depletion of tryptophan.
