[Anti-PD-1 Antibody Drugs - Potential of Plasma PD-L1 Protein as a Biomarker].

Abstract The superior therapeutic effects of antibodies targeting immune checkpoints have been reported in the treatment of various cancers including non-small cell lung cancer(NSCLC)and malignant melanoma. However, the risk of reactivity against selfantigens and the high prices of these drugs are major concerns. Previously, PD-L1 protein expression and the number of infiltrating T cells in tumor tissues were investigated by immunohistochemical staining, as biomarkers for therapeutic anti-PD- 1 antibodies. However, further research into the clinical significance of PD-L1 expression in tumor tissues is still required. A promising and comprehensive gene mutation analysis of tumor tissues and T cell repertoire analysis has recently been undertaken. Liquid biopsy, which has the benefit of being minimally invasive, has also been investigated. We are currently, investigating the utility of plasma PD-L1 protein levels as a predictive biomarker of prognosis in NSCLC. Furthermore, it is important to explore useful biomarkers and develop reliable companion diagnostics for the individualized treatment with immune checkpoint drugs.