Near Infrared-Photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment 
that employs an antibody-photo-absorber conjugate (APC). Programmed cell death 
protein-1 ligand (PD-L1) is emerging as a molecular target. Here, we describe 
the efficacy of NIR-PIT, using fully human IgG1 anti-PD-L1 monoclonal antibody 
(mAb), avelumab, conjugated to the photo-absorber, IR700DX, in a PD-L1 
expressing H441 cell line, papillary adenocarcinoma of lung. Avelumab-IR700 
showed specific binding and cell-specific killing was observed after exposure of 
the cells to NIR in vitro. In the in vivo study, avelumab-IR700 showed high 
tumor accumulation and high tumor-background ratio. Tumor-bearing mice were 
separated into 4 groups: (1) no treatment; (2) 100 μg of avelumab-IR700 i.v.; 
(3) NIR light exposure only, NIR light was administered; (4) 100 μg of 
avelumab-IR700 i.v., NIR light was administered. Tumor growth was significantly 
inhibited by NIR-PIT treatment compared with the other groups (p < 0.001), and 
significantly prolonged survival was achieved (p < 0.01 vs other groups). In 
conclusion, the anti-PD-L1 antibody, avelumab, is suitable as an APC for 
NIR-PIT. Furthermore, NIR-PIT with avelumab-IR700 is a promising candidate of 
the treatment of PD-L1-expressing tumors that could be readily translated to 
humans.