GZMK expression within activated intratumoral T-cell subsets reflects differentiation efficiency and predicts response to cancer immunotherapy.

Neoadjuvant immunotherapies (NITs) have demonstrated clinical benefit in head and neck carcinoma and other cancers by enhancing T cell-mediated anti-tumor immunity. However, disease recurrence remains a major challenge in a significant proportion of patients. Characterization of T cell dynamics underlying NIT outcomes may lead to improved treatment strategies. Here, we identify baseline intratumoral T cell differentiation efficiency as a predictor of response to NIT. Clonal analysis of tumor-emergent T cells post-treatment revealed granzyme K (GZMK) expression within differentiated subsets as a marker of recent differentiation. Efficient pre-treatment differentiation of GZMK+ progenitor T cells toward activated effectors predicts increased treatment-induced tumor regression. Consistently, pre-treatment tumor-infiltrating T cell clones predominantly adopt either exhausted, tissue-resident memory-like, or peripherally enriched GZMK+ progenitor states, implicating impaired intratumoral differentiation in limited anti-tumor immunity at baseline. Together, our findings demonstrate that GZMK+ T cell profiles reflect baseline anti-tumor immunocompetence and offer a clinically actionable biomarker for predicting immunotherapy response. NCT04247282, ClinicalTrails.gov, registered 1/30/2020 and NCT03429036, ClinicalTrails.gov, registered 11/06/2020.