NCIt definition : A radioimmunoconjugate composed of atezolizumab, a humanized, Fc-optimized, monoclonal
antibody directed against programmed cell death-1 ligand 1 (PD-L1) and labeled with
the radioisotope zirconium Zr 89, with potential use for assessing PD-L1-expressing
tumor cells using positron emission tomography (PET). Upon administration of zirconium
Zr 89-labeled atezolizumab, the antibody moiety targets and binds to PD-L1. Following
tumor cell uptake, the radioisotope moiety can be visualized using PET. This may result
in the quantification of PD-L1-expressing tumor cells, an assessment of the expected
response to treatment with atezolizumab as well as selection of patients that would
respond to atezolizumab. PD-L1 is overexpressed on many human cancer cell types; PD-L1
binding to programmed cell death 1 (PD-1) on T-cells suppresses the immune system
and results in increased immune evasion.;