Figure 2. [⁶⁴Cu]WL12 shows specificity to PD-L1 in vitro.

A, Competitive inhibition assay demonstrating the affinity of WL12 analogs for inhibiting PD-1:PD-L1 interaction; B, Flow cytometry histograms of cell lines used for in vitro studies show variable PD-L1 expression, BD-MIH1-PE is phycoerythryn conjugated anti human PD-L1 antibody; C, [⁶⁴Cu]W12 shows increased binding to cells with high PD-L1 expression which could be blocked by excess peptide (PEP). Significance is indicated by asterisks (*) and the comparative reference is uptake by cell line with low PD-L1 expression or uptake at the blocking dose. ***P < 0.001.