Recent advancements in cancer immunotherapy have improved patient outcomes, yet responses to immunotherapy remain moderate. Immunosenescence has been shown to contribute to the development and progression of various diseases; however, its specific role in solid tumors has not been fully delineated. Here we conducted a phase 2 clinical trial involving 51 patients with cancer undergoing neoadjuvant chemoimmunotherapy and applied single-cell RNA as well as TCR and BCR sequencing on tumor and blood samples to elucidate the immune cell perturbations. Our findings associate poor response with reduced levels of CCR7+ CD4+ naive T cells and CD27+ memory B cells, as well as higher expression of immunosenescence-related genes in T and B cell subsets. Using naturally aged mice and Ercc1-deficient mice (premature aging), we found that senolytics enhance the therapeutic efficacy of immunotherapy in multiple solid tumors by mitigating immunosenescence. Notably, we launched a phase 2 clinical trial (COIS-01) investigating the combination of senolytics with anti-PD-1 therapy. The results showed that the combination therapy achieved a 33.3% (95% confidence interval 16.6-54.7%) major pathological response rate with a low incidence of grade 3-4 adverse events (4.2%). These findings underscore the pivotal role of immunosenescence characteristics in influencing the effectiveness of immunotherapy and suggest a promising therapeutic efficacy along with a favorable safety for the combination of senolytics with anti-PD-1 therapy. ClinicalTrials.gov Identifier: OOC-001( NCT04718415 ) and COIS-01( NCT05724329 ).
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