Biodistribution and fit of displacement curve. (A) Biodistribution of 111In-labelled PP-F11 with increasing excess unlabelled peptide in nude mice (N = 5) with CCK2R-transfected A431 tumour xenografts at 2 h after injection, showing saturation of uptake in the CCK2R tumours and stomach. (B) Fit of displacement radioactivity curve to the CCK2R tumour xenograft data with log(ED50) = −9.30 × 0.19 (ED50 = 0.51 nmol (95% CI: 0.2 to 1.2), correlation R2 = 0.80). (C) Fit of displacement curve to stomach uptake data with log(ED50) = −10.54 × 0.38 (ED50 = 0.03 nmol (0.005 to 0.17), R2 = 0.85). Error bars indicate standard deviations of the mean values.