Development of [F]FPy-WL12 as a PD-L1 Specific PET Imaging Peptide.

Expression of programmed cell death ligand 1 (PD-L1) within tumors is an important biomarker for guiding immune checkpoint therapies; however, immunohistochemistry-based methods of detection fail to provide a comprehensive picture of PD-L1 levels in an entire patient. To facilitate quantification of PD-L1 in the whole body, we developed a peptide-based, high-affinity PD-L1 imaging agent labeled with [F]fluoride for positron emission tomography (PET) imaging. The parent peptide, WL12, and the nonradioactive analog of the radiotracer, FPy-WL12, inhibit PD-1/PD-L1 interaction at low nanomolar concentrations (half maximal inhibitory concentration [IC], 26-32 nM).

Peptide-Based Ga-PET Radiotracer for Imaging PD-L1 Expression in Cancer.

Tumors create and maintain an immunosuppressive microenvironment that promotes cancer cell escape from immune surveillance. The immune checkpoint protein programmed death-ligand 1 (PD-L1) is expressed in many cancers and is an important contributor to the maintenance of the immunosuppressive tumor microenvironment. PD-L1 is a prominent target for cancer immunotherapy.