CLDN4 and neoplasm: As expected, tracer clearance from blood was fast, resulting in good tumor-to-blood ratios in PSN-1 xenograft–bearing mice at 90 min after injection of the tracer, all significantly higher than for the claudin-4–negative controls except for [111In]In-cCPES307A+N309A+S313A ([111In]In-cCPE194–319: 1.7 ± 0.3 vs. 0.3 ± 0.1, P < 0.01; [111In]In-cCPES313A: 1.7 ± 0.8 vs. 0.3 ± 0.1, P < 0.01; [111In]In-cCPES307A+N309A+S313A: 1.4 ± 0.2 vs. 0.7 ± 0.7, P > 0.05; [111In]In-cCPED284A: 4.3 ± 0.2 vs. 0.6 ± 0.2, P < 0.001; [111In]In-cCPEL254F+K257D: 2.2 ± 0.2 vs. 0.5 ± 0.1, P < 0.001).