Dual immune checkpoint blockade induces analogous alterations in the dysfunctional CD8+ T cell and activated Treg compartment. Dual immune checkpoint blockade induces analogous alterations in the dysfunctional CD8+ T cell and activated Treg compartment

Immune checkpoint blockade has shown clinical activity in a range of cancer types. To dissect the effect of neoadjuvant PD-1 and CTLA4 blockade on intratumoral T cells in treatment-naïve head and neck squamous cell carcinoma, we analyzed immune infiltrates in tumor biopsies from responding and non-responding patients. At baseline, a higher ratio between active (4-1BB/OX-40+) and inactive regulatory CD4+ T cells was associated with response to therapy. Furthermore, upon therapy, this active Treg population showed a profound decrease in responding patients. In an analogous process, the intratumoral dysfunctional CD8+ T cell compartment displayed a decrease in the expression of activity and dysfunction-related genes in responding patients, while in clinically non-responding patients, NK cells showed an increased cytotoxic transcriptional profile early upon treatment. These data reveal the immunological changes in response to dual PD-1 and CTLA4 blockade, including a parallel remodeling of presumed tumor-reactive T cell compartments in responding patients, and indicate that the presence of an activated Treg compartment at baseline may be associated with response. Overall design: We performed single cell RNA and TCR sequencing (10x Genomics) on immune infiltrates (CD45+ cells) from 18 HNSCC patients enrolled in the IMCISION trial (Vos et al. 2021). Viable immune cells were isolated from pre-treatment and on-treatment primary tumor biopsies of 10 patients responding (1 partial pathological response and 9 major pathological responses) and 7 patients non-responding to anti-PD-1 and anti-CTLA4 combination immunotherapy. One patient treated with anti-PD-1 monotherapy (1 major pathological response) was included in the dataset. *** Raw sequencing data will be deposited on EGA. ***