Definition

A radiotracer composed of the programmed cell death-1 ligand 1 (PD-L1; cluster of differentiation 274; CD274)-binding peptide WL12 radiolabeled with the radionuclide gallium Ga 68, with potential PD-L1 imaging activity using positron emission tomography (PET). Upon administration of gallium Ga 68-WL12, the WL12 moiety targets and binds to PD-L1 expressed on certain tumor cells. Upon uptake and PET imaging, the radioisotope moiety can be visualized and the extent of PD-L1 expression can be assessed. This may be used to predict the therapeutic response to PD-L1-targeting agents.