FIGURE 2.

cIAP1/2 antagonism synergizes with checkpoint blockade in immunogenic PDAC. (A) KPC.1 cells (150,000) were inoculated s.c. into C57BL/6 mice that were treated with LCL-161 (75 mg/kg) or vehicle by oral gavage every 3 d starting on day 5 postinoculation. (B) Cured mice from (A) were rechallenged with 300,000 KPC.1 cells. n = 4. (C) Spleen cells of n = 4 rechallenged mice were restimulated with KPC.1 cells or a different PDAC cell line (Panc02) and analyzed by IFN-γ ELISPOT. (D) KPC.1 cells were suspended in Matrigel and implanted orthotopically in the pancreas of C57BL/6 mice and treated with LCL-161 and the indicated checkpoint blockade Abs (200 μg/mouse, twice weekly). Tumors were analyzed at day 21. Results are representative of two independent experiments. (E) Photograph of tumors from (D). An “X” indicates no tumor was detected. (F) KPC.1 cells were irradiated and injected s.c. into C57BL/6 mice that were also inoculated orthotopically with 50,000 live KPC.1 cells suspended in Matrigel. Mice were dosed with vehicle or LCL-161 (75 mg/kg) by oral gavage every 3 d starting on day 4. Tumors were harvested at day 21. Results are representative of three independent experiments. (G) Orthotopic tumors from mice treated as in (D) were digested and analyzed by flow cytometry for CD8 T cell infiltrates. Values are out of total CD45⁺ cells. Results are representative of five independent experiments. (H) C57BL/6 mice were inoculated orthotopically with 50,000 KPC.1 cells in Matrigel and treated with vehicle or LCL-161 (75 mg/kg) by oral gavage every 3 d starting on day 4. Mice were also treated with depleting Abs to CD4, CD8, both CD4 and CD8, or isotype control (150 μg/mouse) twice weekly starting on the day of tumor inoculation. Tumors were harvested at day 18. Error bars are SEM throughout. A Mann–Whitney t test was used for statistical analysis.