27P - Single cell RNA sequencing (scRNAseq) analysis of peripheral immune cell populations from patients treated with anti-PD1 with recurrent and/or metastatic squamous cell carcinoma of the head and neck (R/M SCCHN)

Background

In R/M SCCHN, only 15-20% of patients experience sustained long-term benefit from PD-1 inhibitors. The PD-L1 combined positive score (CPS) from tumor biopsies alone is insufficient to accurately predict treatment response. Immune cell composition and gene expression profiles measured in peripheral blood mononuclear cells (PBMCs), can provide a less invasive and repeatable method to monitor the dynamics of treatment response over time.

Methods

We prospectively collected PBMCs from a cohort of 60 R/M SCCHN patients undergoing anti-PD-1 monotherapy. Patients were divided into two groups (responders and non-responders) based on their best treatment response (RECIST v1.1 criteria). PBMCs were collected before (baseline) and 8-12 weeks (on-treatment) after treatment initiation. Exploratory transcriptomic and proteomic analyses were performed on a limited number of patients using scRNAseq and CITEseq. Cells were processed using the 10x Genomics Chromium Next GEM Single Cell 3’ platform. This study aims to identify biomarkers predictive of response or resistance to anti-PD-1 therapy.

Results

A total of approximately 150,000 immune cells were annotated from 18 paired samples (baseline and on-treatment) from 5 responders and 4 non-responders. Our initial analysis focused on the CD8+ T cell population, within which seven distinct clusters were identified. An exhausted CD8+ T cell phenotype with a highly activated profile (PDCD1^hiTIGIT^hiGZMA^hiNKG7^hiGNLY^hi) was enriched in responders, in the baseline and on-treatment samples. In contrast, two distinct exhausted CD8+ T cell phenotypes were more prevalent in non-responders. One displayed sign of TGF-β signaling (SMAD7⁺) (in the baseline samples), while the other showed higher expression of various inhibitory checkpoints such as LAG3, TIM3, and CTLA4 compared to responders.

Conclusions

Analysis of peripheral immune cell populations may serve as a predictive biomarker for PD-1 inhibitor efficacy in R/M SCCHN. Additional samples are currently being analyzed, and flow cytometry panels will be established to confirm these findings in larger and independent cohorts.

Legal entity responsible for the study

The authors.

Funding

FNRS.

Disclosure

S. Carlier: Financial Interests, Personal, Other, travel expanse: Merck, Teva. S. Lucas: Financial Interests, Personal, Advisory Board, Consultancy fees for participation to 3 AbbVie Solid Tumor Advisory boards: AbbVie; Financial Interests, Personal, Stocks/Shares, Received stock options as consultant and collaborator of the biotech company Argenx (Ghent, Belgium): Argenx; Financial Interests, Institutional, Royalties, Co-inventor on a patent deposited by the UCLouvain and Argenx covering anti-GARP:TGFb1 antibody. Antibody was licensed to argenx and sublicensed to AbbVie, leading to royalty payments to the UCLouvain (Université Catholique de Louvain, Brussels, Belgium): Argenx; Financial Interests, Institutional, Local PI, Research Service Agreement funding work in my laboratory (UCLouvain - de Duve Institute): Argenx; Financial Interests, Institutional, Local PI, Sponsored Research agreement for translational research on patient-derived material from clinical trial testing livmoniplimab: AbbVie. J. Machiels: Financial Interests, Institutional, Advisory Board: Novartis, MSD, Pfizer, Roche, Debio, AstraZeneca, Innate, Nanobiotix, Bayer, Boehringer Ingelheim, BMS, Pfizer, Cue Pharma, Incyte, Janssen, Johnson & Johnson, ALX Oncology, F-star, Nektar, F-star, Seagen, Astellas, Genmab, Merus, GSK, CureVac; Financial Interests, Institutional, Advisory Board, Education: Merck-Serono; Financial Interests, Institutional, Other, Travel expense: Gilead, MSD, Sanofi; Financial Interests, Institutional, Steering Committee Member: AstraZeneca, MSD; Financial Interests, Institutional, Coordinating PI: MSD, iTeos, eTheRNA; Financial Interests, Institutional, Local PI: Pfizer, Celyad, MSD, Novartis, KURA, Roche, Lilly, Boehringer, Sanofi-Aventis, Incyte, Bayer, Merck - Serono, Janssen, Johnson & Johnson, Amgen, AbbVie, GSK; Non-Financial Interests, Personal, Leadership Role, Chair: EORTC head and neck group. All other authors have declared no conflicts of interest.