The clinical activity of ipilimumab, for instance, correlated well with high baseline expression of FoxP3 and indoleamine 2,3-dioxygenase (IDO), an immunoregulatory enzyme that suppresses T-cell responses, and high numbers of tumor-infiltrating lymphocytes in a prospective phase II clinical trial and these markers may thus be of use in patient selection [232]. This evidence concerns the gene IDO1 and neoplasm.