Compositions and methods relating to detection, inhibition, and imaging of indoleamine 2,3-dioxygenase 1 (IDO1)

A heterobiligand comprising a first ligand having affinity for an epitope on indoleamine 2,3-dioxygenase 1 (IDO1), a linker, and a second ligand, wherein the second ligand comprises a small molecule inhibitor of IDO1, wherein the linker links the first ligand and the second ligand, wherein the heterobiligand specifically binds and inhibits IDO1, wherein IDO1 comprises an active site, and wherein the small molecule inhibitor of IDO1 binds the IDO1 active site, wherein the first ligand comprises an amino acid sequence selected from the group consisting of wyvay (SEQ ID NO:2), wyaay (SEQ ID NO:

• 8), (F-Phe)n(Me-Trp)(Me-Trp)w (SEQ ID NO:5), (F-Phe)rhl(Me-Trp) (SEQ ID NO:
• 9), (F-Phe)t(Me-Trp)y(Me-Trp) (SEQ ID NO:10), G(F-Phe)nwk (SEQ ID NO:11), (Me-Trp)ffkf (SEQ ID NO:12), ndn(Me-Trp)w (SEQ ID NO:13), npv(F-Phe)w (SEQ ID NO:
• 14), ntk(Me-Trp)p (SEQ ID NO:15), n(Me-Trp)p(Me-Trp)f (SEQ ID NO:16), pp(Me-Trp)s(Me-Trp) (SEQ ID NO:17), yyy(Me-Trp)t (SEQ ID NO:18), and yfn(Me-Trp)(Me-Trp) (SEQ ID NO:19);
• and
• wherein the small molecule inhibitor of IDO1 is
• wherein X is S, O, or NH, wherein R1 is —CH2—R2—, —(CH2)n—R2—, absent, —(CH2—CH2—O)m—CH2—CH2—R2—, or —CH2—CH2—NH—SO2—R2—, wherein R2 is —CO— or —NH—, wherein n is an integer from 2 to 10, wherein m is an integer from 1 to 6.