[64Cu]Cu–DOTA–HAC–PD-1, in PD-L1–negative tumours or hPD-L1–positive tumours blocked by unlabelled HAC–PD-1, lacked uptake signals which indicated a high degree of specificity of [64Cu]Cu–DOTA–HAC–PD-1 for PD-L1 binding.320 By using multiple PD-L1 inhibitors approved for marketing by the FDA, researchers have subsequently developed new radiopharmaceuticals based on approved drugs that are already in the clinical stage. The gene discussed is PDCD1; the disease is neoplasm.