Overall initial tumor uptake at 1.5 h p.i. was low (SUVmax < 2) for all compounds, with [64Cu]Cu-1 and [64Cu]Cu-4 showing the highest specific uptake (SUVmax = 1.6 and 1.8) and best contrast (152% and 135% higher uptake in PD-L1 vs. mock tumor). The gene discussed is CD274; the disease is neoplasm.