Abstract 1268: Anti-PD-1 monotherapy outperforms multiple immunotherapy combination strategies in an oral cancer prevention mouse model
Authors: Novaes Jose Augusto Monteiro de Oliveira , Pisegna Marlese A. , Poteete Alissa , Zhang Fahao , Heymach John V. , William William N. 
Published: August 2018

Abstract
Oral premalignant lesion (OPL) expression of PD-L1 is associated with increased cancer risk. These data suggest that immune evasion is already present at the OPL stage and warrant an evaluation of immune modulatory therapies for cancer prevention. We conducted this preclinical study in a carcinogen-induced mouse model of oral cancer to evaluate the efficacy of multiple immunomodulatory strategies, given at a time point when only OPLs are present, to reduce the incidence of oral squamous cell carcinoma (OSCC).
We treated C57BL/6 mice with the carcinogen 4-nitroquinoline 1-oxide (4-NQO) for 8 weeks in drinking water. Eight weeks after discontinuing 4-NQO treatment, a group of mice (N=6) was sacrificed for assessment of invasive and non-invasive tongue lesions. A second group of mice was treated with either anti-PD-1 (N=40), anti-CTLA-4 (N=20), anti-OX40 (N=20), anti-PD-1 + anti-CTLA-4 (N=20), anti-PD-1 + anti-OX40 (N=20) antibodies, or IgG (N=40) for a total of 3 doses every 3 days, initiating 8 weeks after the cessation of 4-NQO. Antibodies used in combination were given on the same day . Mice were sacrificed 56 days after the last dose of treatment. We assessed serial H&E-stained cross sections of the tongues harvested at that same time point for development of OPLs and cancer and measured the OSCC area of each tongue using aperio imagescope software. Mann-Whitney and Fisher's exact tests were used for statistical comparisons between groups.
Eight weeks after 4NQO cessation, 100% of mice developed tongue hyperplasia or dysplasia and invasive lesions were not identified, indicating this to be an ideal time point to initiate treatment strategies addressing OPLs. Tongues from mice treated with anti-PD-1 antibody displayed a decrease in the mean OSCC area when compared with mice treated with IgG (mean 3.53 mm2 versus 6.62 mm2, respectively; p= 0.018). At this time point, invasive oral cancers had developed in 75% versus 50% of IgG and anti-PD-1 treated mice, respectively (p=0.03). There were also non-significant decreases in the mean OSCC area in tongues from mice treated with anti-CTLA-4 (mean = 5.07 mm2), anti-OX40 (mean = 3.79 mm2) and anti-PD-1 + anti-CTLA-4 (mean = 3.86 mm2) antibodies when compared to mice treated with IgG (mean = 6.62 mm2) control. In the group treated with anti-PD-1 + anti-OX40 combination therapy, there was an increase in the mean OSCC area when compared to anti-PD-1 monotherapy (mean 3.53 mm2 versus 9.03 mm2), respectively (p= 0.01).
Short-term anti-PD-1 immune checkpoint inhibitor therapy in the context of OPLs led to a reduction in the incidence of oral cancer. When comparing the mean area of OSCC in each group, anti-PD-1 monotherapy was superior to IgG and all other treatment strategies. Paradoxically, combining anti-OX40 and anti-PD-1 antibodies created an antagonizing effect on the therapy and increased total tumor burden when compared with anti-PD-1 monotherapy.
Citation Format: Jose Augusto Monteiro de Oliveira Novaes, Marlese A. Pisegna, Alissa Poteete, Fahao Zhang, John V. Heymach, William N. William. Anti-PD-1 monotherapy outperforms multiple immunotherapy combination strategies in an oral cancer prevention mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1268.