Systemic CD4 immunity: A powerful clinical biomarker for PD‐L1/PD‐1 immunotherapy

The search for non‐invasive systemic biomarkers of response to PD‐L1/PD‐1 blockade immunotherapy is currently a priority in oncoimmunology. In contrast to classical tumor biomarkers, the identification of clinically useful immunological biomarkers is certainly a challenge, as anti‐cancer immune responses depend on the coordinated action of many cell types. Studies on the dynamics of systemic CD8 T‐cell populations have provided indications that such biomarkers may have a place in clinical practice. However, the power of CD8 T‐cell subsets to discriminate clinical responses in immunotherapy has so far proven to be limited. The systemic evaluation of CD8 T‐cell regulators such as myeloid cells and CD4 T cells may provide the solution. Here we discuss the value of systemic quantification of CD4 T‐cell subsets for patient selection in light of the results obtained by Prof. Kagamu′s and our team. Our studies have independently demonstrated that the evaluation of the pre‐treatment status of systemic CD4 immunity is a critical factor for the clinical outcome of PD‐L1/PD‐1 blockade therapy with robust predictive capacities.