CD8A and neoplasm: It has been observed that due to IDO inhibition, apoptosis occurs in Treg cells and not in CD8 + T cells, which play a key role in tumor defense11.To date, several IDO inhibitors including 1-methyl-L or D-tryptophan, brasinin and its derivatives (Navoximod (NLG-919), Indoximod, BMS-986205 and Epacadostat (INCB024360) have been investigated in various studies12–14.