Epacadostat (previously INCB24360) is an investigational drug for cancer.

[1][2][3] Epacadostat inhibits IDO1 by competitively blocking it, without interfering with IDO2 or tryptophan 2,3-dioxygenase (TDO).

It has antitumor activity in some models, though is most effective when combined with other immunotherapy agents.

[4] As of 2017, the combination of epacadostat with pembrolizumab (Keytruda) was being investigated by Incyte and Merck & Co. in several cancers, as was the combination of epacadostat with nivolumab (Opdivo) by Incyte and Bristol Myers Squibb.

[5] In April 2018, Incyte announced they were halting the Phase III ECHO-301/KEYNOTE-252 (NCT02752074) trial of epacadostat with pembrolizumab for melanoma as the combination therapy missed the first primary endpoint of improving progression-free survival vs. pembrolizumab alone.