Activation of memory/effector T cells and association between prognosis and OX40-positive T cells in advanced head and neck cancer patients treated with anti-programmed death-1 antibody.

35 Background: Anti-programmed death-1 (PD-1) monoclonal antibody, nivolumab, enhances anti-tumor activity by inhibiting the interaction of PD-1 and programmed death-1 ligand 1 and has shown efficacy for platinum-refractory recurrent or advanced head and neck cancer (HNC). However, subsets of immune cells predominantly activated during the period of anti-PD-1 therapy for HNC and specifically associated with the prognosis have not been clarified. Methods: Peripheral blood mononuclear cells of 15 HNC patients treated with nivolumab were prospectively obtained before the initial and second administrations of nivolumab, and at the time of progressive disease (PD). We performed comprehensive analysis of the proportion of immune cell subsets by flow cytometry, including the expression of coinhibitory and costimulatory molecules such as T-cell immunoglobulin and mucin domain 3 (TIM-3), lymphocyte-activation gene 3 (LAG-3), T-cell immunoreceptor with Ig and ITIM domains (TIGIT), B and T lymphocyte attenuator (BTLA), CD28, OX40, inducible T cell costimulator (ICOS). Association between changes in the proportion of the subsets and therapeutic effect were also analyzed. Results: Median progression free survival (PFS) of the whole patients was 96 days (95% CI 70–308). After a single course of nivolumab, patients showed a significant increase in activated central memory and effector subsets of CD4+/CD8+ T cells and activated helper T1 cells (p = 0.0039, 0.0078, 0.0273, 0.0391, 0.0391). A trend of increase of activated effector memory CD4+/CD8+ T cell was observed (p = 0.4961, 0.3594). At the time of PD, effector regulatory T cells, LAG3 positive CD4+/CD8+ T cells, TIM-3 positive CD4+/CD8 T cells and BTLA positive CD4+/CD8+ T cells significantly increased. Significant positive correlations were found between PFS and the proportion of OX40 positive CD4+/CD8+ T cells before nivolumab therapy (p = 0.0239, 0.0134). Conclusions: Nivolumab therapy enhances activation of central memory and effector subsets of CD4+/CD8+ T cells. The expression level of OX40 on T cells was correlated with efficacy of nivolumab therapy in HNC patients.