INCB024360 analogue is a potent and selective inhibitor of IDO1 with IC50 value of 67 nM. [1]
IDO (indoleamine-pyrrole 2, 3-dioxygenase) is an enzyme which is encoded by the IDO1 gene. IDO is the rate-limiting and first enzyme of tryptophan which is one amino acid of human catabolism through kynurenine pathway. The decrease of L-tryptophan can cause halted growth of T cells as well as microbes. IDO belongs to immunomodulatory enzyme. It is produced by some activated macrophages and immunoregulatory cells. IDO is overexpressed in a wide range of cancer cells such as lung, prostatic, pancreatic, colorectal cancer. It is indentified to help cancer cells to escape the immune system by reducing the level of L-tryptophan in the microenvironment of cells.[2]
In Hela cells, INCB024360 analogue selectively inhibited the activity of human IDO1 with IC50 value of 19 nM. On the other hand, INCB024360 analogue demonstrated little inhibition activity against TDO (tryptophan 2, 3-dioxygenase). In murine B16 cells, INCB024360 analogue inhibited IDO with IC50 value of 46 nM [1].
In naive C57BL/6 mice, 100 mg/kg INCB024360 analogue injected subcutaneously reduced kynurenine levels by >50% via inhibition of IDO activity. In C57BL/6 mice bearing GM-CSF- secreting B16 tumors, INCB024360 analogue (25, 50, and 75 mg/kg b.i.d.) injected subcutaneously for 14 days dose-dependently inhibited tumor growth [1].
References:
[1]. Yue EW1, Douty B, Wayland B, et al. Discovery of potent competitive inhibitors of indoleamine 2,3-dioxygenase with in vivo pharmacodynamic activity and efficacy in a mouse melanoma model. J Med Chem. 2009 Dec 10;52(23):7364-7.
[2]. Uyttenhove C, Pilotte L, Theate I, Stroobant V, Colau D, Parmentier N, Boon T, Van den Eynde BJ: Evidence for a tumoral immune resistance mechanism based on tryptophan degradation by indoleamine 2,3-dioxygenase. Nat Med 2003, 9(10):1269-1274.