Anti-tumor activity of an anti-DR5 monoclonal antibody, TRA-8, in combination with taxane/platinum-based chemotherapy in an ovarian cancer model.

Objective: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) mediates apoptosis via binding to death receptors and enhances the anti-tumor effect of conventional cancer therapies. We evaluated the efficacy of TRA-8, an agonistic antibody to DR5, combined with docetaxel and carboplatin in vitro in an intraperitoneal (IP) ovarian cancer model.

Methods: Luciferase positive ES2 cells (ES2H) were treated in 96 well plates with TRA-8, carboplatin, docetaxel, and combination therapy. Cell viability was assessed using ATP-lite assay. Apoptosis was confirmed via Western blot analysis. ES2H cells were injected IP into female athymic nude mice. Animals were sorted based on bioluminescent signal with the following treatments: 1) untreated; 2) TRA-8 alone; 3) docetaxel+carboplatin; and 4) docetaxel+carboplatin+TRA-8. Animals receiving TRA-8 antibody were injected IP with 200 μg of TRA-8 twice weekly until death. Animals receiving docetaxel+carboplatin were injected IP with 5mg/kg and 15 mg/kg respectively every 3 weeks until death. Animals were assessed for tumor burden using bioluminescence imaging and overall survival.

Results: Combination therapy reduced viability of ES2H cells in vitro over single agent therapy. Tumor burden was lowest in the chemotherapy+TRA-8 group at days 23 (p<0.001) and 30 (p = 0.04). Mean survival was greatest in the chemotherapy+TRA-8 group (41 days) compared to the chemotherapy only group (34 days) and control group (27 days) as determined by Kaplan-Meier analysis (p<0.001).

Conclusion: Conventional chemotherapy combined with TRA-8 reduced cell-viability via activation of apoptotic pathways, reduced tumor burden and improved survival in this ovarian cancer model.