Distinct CD8⁺ T cell dynamics associate with response to neoadjuvant cancer immunotherapies

We leverage a clinical trial (NCT04080804) that compared neoadjuvant anti-PD-1, anti-PD-1+CTLA-4, and anti-PD-1+LAG-3 therapies in head and neck squamous cell carcinoma patients. Combination therapies promote higher pathologic response rates versus monotherapy, and major pathologic response is associated with better survival. To address whether successful immune checkpoint inhibitor (ICI) regimens act through similar or distinct pathways, we robustly and longitudinally characterize transcriptional and proteomic dynamics of CD8⁺ tumor-infiltrating lymphocytes (TILs) in a clonal manner. Anti-PD-1+LAG-3 reprograms CD8⁺ TIL with type-I interferon response and exhaustion gene programs into effector memory and resident memory (T_EM/T_RM). In contrast, anti-PD-1+CTLA-4 activates and expands pre-existing T_EM/T_RM CD8⁺ TIL, but does not rejuvenate exhausted phenotypes into T effector cells. Anti-PD-1+LAG-3, but not anti-PD-1+CTLA-4, induces widespread TCR sharing among the different transcriptional states, as well as increased TCR diversity in responding patients. Our data suggest doublet regimen-specific transcriptional and clonal dynamics of tumor-reactive CD8⁺ T cells.