IDO-blockade synergizes with chemo-radiation therapy. Orthotopic GL261 glioblastoma tumors were implanted stereotactically into the right frontal lobes of syngeneic C57BL/6 host mice. Kaplan-Meier survival plots are shown, comparing mice treated with: A, temozolomide plus radiation (TMZ + RT) and with or without IDO-blockade using DL-1MT; B, TMZ + RT and with or without IDO-blockade using NLG919 or D-1MT; C, cyclophosphamide plus RT (CPM + RT) and with or without DL-1MT; or D, with CPM + RT plus either D-1MT or DL-1MT. IDO-blocking drugs (DL-1MT, 4 mg/mL; NLG919, 6 mg/mL; or D-1MT, 4 mg/mL) were supplied in drinking water continuously starting at day 7 after tumor implantation; chemotherapy (TMZ, 100 mg/kg, i.p.; or CPM, 100 mg/kg, i.p.) was given on day 9, and RT (500 cGy) was given on day 10. For reference, each survival plot contains a cohort of untreated mice, and mice treated with IDO-blockade using DL-1MT alone are shown in A. Cohort sizes (n) are indicated for each treatment group and represent pooled data from multiple experiments containing 1–3 mice from each group per experiment. n.s., not significant [vs. untreated mice (A); or DL-1MT vs. D-1MT (D)]; *, P < 0.001 (vs. untreated mice); **, P < 0.002 (vs. mice treated with chemo-radiation alone), by log-rank test.