Selective inhibition of IDO1, D-1-methyl-tryptophan (D-1MT), effectively increased EpCAM/CD3-bispecific BiTE antibody MT110 efficacy against IDO1breast cancer via enhancing immune cells activity.

MuS110 and MT110 are BiTE antibodies bispecific for CD3 and EpCAM, which is the most frequently and highly expressed tumor-associated antigen on breast cancer. And pronounced expression of IDO1 has also been reported in breast cancer. Our study aimed to investigate whether IDO1 inhibitor D-1MT combing with MuS110/MT110 had synergistic antitumor effects on IDO expressing EpCAM-positive breast cancer cells in vitro and in vivo.