Project 3: Determining biomarkers for responsiveness to immunotherapy targeting LAG3/PD1 in HNSCC

PROJECT SUMMARY – PROJECT 3 Although great strides have been made with immunotherapy for head and neck squamous cell carcinoma (HNSCC), there is a strong imperative to [i] gain a better understanding of the mechanism(s) of action for current standard-of-care (SOC) immunotherapies (e.g. anti-PD1) and novel immunotherapeutic treatments in clinical trials (e.g. anti-LAG3); [ii] determine biomarkers of responsiveness that could predict patient outcomes to immunotherapy; and [iii] determine if there are mechanisms of resistance that can be overcome. Tumor- specific inhibitory mechanisms, such as inhibitory receptors (IRs), represent major obstacles to effective anti- tumor immunity, highlighting the importance of understanding their cell intrinsic and extrinsic mechanisms and optimal combinations to improve immunotherapies. Although LAG3 is the third ‘checkpoint’ to be targeted with >10 agents in clinical trials, we still know very little about how LAG3 blockade, alone or with anti-PD1, impacts the immune response to HNSCC. Our over-arching hypothesis is that LAG3/PD1 dual blockade synergizes to promote CD8+ T cell function in the tumor and peripheral blood (PBL) of HNSCC patients, and a LAG3- dominant IR module in peripheral CD8+ T cells downregulates T cell function, and ultimately, patient response to PD1-targeted therapy. We ask two major questions in this area. What is the mechanism of anti-PD1 (nivo) and anti-LAG3 (rela) on the anti-tumor function of CD8+ T cells? We are accruing to a novel neoadjuvant window trial which randomizes treatment-naïve locally advanced HNSCC patients to two arms relevant to this Aim: [i] nivo monotherapy, or [ii] nivo plus rela, followed by surgery after initiation of treatment. We hypothesize that T cell activation and proliferation pathways are differentially regulated by anti-PD1 vs. anti-LAG3 in CD8+ T cells, and that unique synergistic molecular programs will be revealed by this immunotherapeutic combination in treatment-naïve patients with HNSCC. Secondly, we ask whether cytokines drive a LAG3-dominant IR module in peripheral, naive CD8+ T cells and does it predict responsiveness to immunotherapy? We recently made a series of novel findings regarding IR expression in peripheral CD8+ T cells implying a novel mechanism of immune resistance. We hypothesize that cytokine-driven systemic immune dysfunction and subsequent resistance to anti-PD1 therapy is driven by a LAG3-dominant IR module, and that this dysfunction can be ameliorated by anti-LAG3+PD1 blockade. This project will [i] define biomarkers of response and resistance to nivo and nivo/rela, [ii] potentially identify a patient population that will optimally benefit from LAG3-based therapies, and [iii] lead to the development novel combinatorial immunotherapy trials of increased efficacy in HNSCC.