In this report, avelumab, a therapeutic anti-PD-L1 monoclonal immunoglobulin G (IgG) antibody (PD-L1 mAb) was labeled with the longer-lived radionuclide, zirconium-89 (t1/2= 78.4 hours) and evaluated in vitro and in vivo in PD-L1 expressing human tumor cells and mouse xenograft models, respectively. The gene discussed is CD274; the disease is neoplasm.