Editorial: Targeting Indoleamine 2,3-dioxygenases and Tryptophan Dioxygenase for Cancer Immunotherapy.

Competing Interests: LB has participated in an advisory board to Incyte Inc. on epacadostat in melanoma and was invited to give a MSL seminar to Incyte Inc. on IDO (2017). GP declares a conflict of interest due to his role as a co-inventor in the discovery and development of IDO/TDO inhibitor technologies patented by the Lankenau Institute for Medical Research and licensed to Duet Therapeutics, Inc., a private company for which he serves presently as a scientific advisor. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.