Timing of PD-1 Blockade Is Critical to Effective Combination Immunotherapy with Anti-OX40

These results highlight the importance of timing for optimized therapeutic effect with combination immunotherapies and suggest the testing of sequencing in combination immunotherapy clinical trials. Clin Cancer Res; 23(20); 6165-77. ©2017 AACRSee related commentary by Colombo, p. 5999.

Antibodies specific for inhibitory checkpoints PD-1 and CTLA-4 have shown impressive

The concurrent addition of anti-PD-1 significantly attenuated the therapeutic effect of anti-OX40 alone. Combination-treated mice had considerable increases in type I and type II serum cytokines and significantly augmented expression of inhibitory receptors or exhaustion markers CTLA-4 and TIM-3 on T cells. Combination treatment increased intratumoral CD4+ T-cell proliferation at day 13, but at day 19, both CD4+ and CD8+ T-cell proliferation was significantly reduced compared with untreated mice. In two tumor models, sequential combination of anti-OX40 followed by anti-PD-1 (but not the reverse order) resulted in significant increases in therapeutic efficacy. Against MMTV-PyMT tumors, sequential combination was dependent on both CD4+ and CD8+ T cells and completely regressed tumors in approximately 30% of treated animals.Conclusions: These results highlight the importance of timing for optimized therapeutic effect with combination immunotherapies and suggest the testing of sequencing in combination immunotherapy clinical trials. Clin Cancer Res; 23(20); 6165-77. ©2017 AACRSee related commentary by Colombo, p. 5999.