Abstract 5648: Combined immune checkpoint targeting with anti-PD-1 plus anti-CD40 antibodies as the most effective approach to eradicate head and neck squamous cell carcinomas (HNSCCs) in mouse models

Introduction: Immunotherapy with single agent anti-PD-1 antibody confers modest overall survival benefits in patients with recurrent/metastatic HNSCCs. Combined immune checkpoint targeting has shown promising results for melanomas and other solid tumors. Thus, evaluation of combination immunotherapy in animal models specific to HNSCCs could inform prioritization and design of human clinical trials for this disease. We conducted this pre-clinical study to test the hypothesis that combining anti-PD-1 with either anti-CTLA-4 or co-stimulatory immune checkpoint agonist antibodies would be more effective than anti-PD-1 monotherapy in a mouse model of oral carcinoma. We also aimed at identifying the combination regimen with highest anti-tumor activity. Methods: C57BL/6 mice were subcutaneously grafted with 2x106 mouse oral cancer 1 (MOC1) cells derived from a carcinogen-induced tumor molecularly similar to human HNSCC. After 25 days, mice were randomized into one of 12 treatment groups (IgG, or antibodies targeting PD-1, CTLA-4, CD40, OX-40, GITR, 4-1BB, PD-1+CTLA-4, PD1+CD40, PD-1+OX-40, PD-1+GITR, or PD-1+4-1BB), N=8-9 mice/group. Antibodies were administered every 4 days for 3 doses. Tumors were measured twice per week. The primary endpoint was overall survival. Mice were sacrificed when tumor diameter was >2 cm or tumor ulceration was >5 mm. Survival curves were computed using the Kaplan-Meier method and compared using the log-rank (Mantel-Cox) test. Results: In analogy to human clinical trials, anti-PD-1 therapy led to a modest improvement in survival compared to IgG [HR=0.41; 95%CI 0.06-0.53; P=0.015], indicating that this model recapitulates, in part, the effects of immunotherapy in HNSCC patients; none of the animals survived long term. Monotherapy with anti-CTLA-4, anti-CD40, anti-OX-40, or anti-4-1BB also improved survival compared to IgG (P=0.0001, 0.003, 0.02, and 0.003, respectively), but were not more effective than anti-PD-1 alone (P=0.09, 0.12, 0.72, and 0.77, respectively). Combination therapy did not prolong survival compared to anti-PD-1 alone, with the exception of anti-PD-1+ anti-CTLA4 [HR=0.36; 95% CI 0.07-0.6; P=0.016], and anti-PD-1+ anti-CD40 [HR=0.125, 95% CI 0.02-0.24; P=0.0003]. Notably, 50% of mice receiving anti-PD-1+ anti-CD40 antibodies had complete tumor eradication and are alive and disease-free 120 days after tumor grafting. Conclusions: Single agent immunotherapy targeting PD-1, CTLA-4, CD40, OX-40 and 4-1BB modestly improved survival in a mouse model of oral cancer. Combination with anti-PD-1+ anti-CTLA4 and anti-PD-1+ anti-CD40 antibodies outperformed anti-PD-1 monotherapy. Complete responses were exclusively seen with PD-1+CD40 dual targeting. This regimen should be prioritized for evaluation in HNSCC clinical trials. Citation Format: Jose Augusto Monteiro de Oliveira Novaes, Alissa R. Poteete, Marlese A. Pisegna, Uma Giri, Fahao Zhang, Patrick Hwu, John V. Heymach, William N. William. Combined immune checkpoint targeting with anti-PD-1 plus anti-CD40 antibodies as the most effective approach to eradicate head and neck squamous cell carcinomas (HNSCCs) in mouse models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5648. doi:10.1158/1538-7445.AM2017-5648