Bispecific Antibody Pretargeting PET (ImmunoPET) with an ¹²⁴I-Labeled Hapten-Peptide

Whole-body γ-images of ¹³¹I-IMP-325 in animals given hBS14 bs-mAb 24 h earlier (+ bs-mAb) or animals given only peptide alone (− bs-mAb). Images on the right show pretargeting under the same conditions using ¹¹¹In-IMP-288. T = tumor; UB = urinary bladder. Arrows show tumor location on photographs of animals.

Focus 120 microPET images of ¹²⁴I-IMP-325 pretargeted with hBS14 (A, C, and D) or alone (not pretargeted; B). (A) From left to right, photograph of AN1, 2 transverse slices (0.82 mm) at level of tumor (arrows) and kidneys (K), taken ∼2 h after injection, and coronal slices obtained at ∼2, 6, and 24 h after injection. (B) From left to right, sagittal and coronal views obtained 1.9 h after injection. (C) From left to right, photograph of AN3 and coronal slices obtained at ∼2, 6, and 24 h after injection. (D) From left to right, coronal slices obtained at ∼2, 6, and 24 h after injection. All pretargeted images are adjusted to same intensity as 2-h image for each animal to illustrate retention and clearance of ¹²⁴I-IMP-325 over time. At 24-h necropsy, tumors were 0.448, 0.285, and 0.483 g in pretargeted animals and 0.472 g in animal given ¹²⁴I-IMP-325 alone. H = heart; S = stomach; Thy = thyroid; UB = urinary bladder.

Focus 120 microPET images of 3 animals injected with ¹²⁴I-hMN-14 Fab′. (A) Transverse slices (0.82-mm thick) in same plane to highlight tumor (arrows) localization at ∼2, 6, and 24 h, from top to bottom, respectively, for each animal. Six-hour images are taken at same intensity as 2-h images, but intensity was increased substantially for 24-h images. Coronal sections taken from 2-, 6-, and 24-h intervals (B, C, and D, respectively) illustrate elevated uptake of radiolabeled Fab′ initially in kidneys (K) and stomach (S). Uptake in these tissues was cleared over time, but there was persistent thyroid (Thy) uptake. Tumor weights at necropsy (24 h) were 0.596, 0.173, and 0.280 g, respectively.