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

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

William J. McBride¹, Pat Zanzonico², Robert M. Sharkey³, Carl Norén¹, Habibe Karacay³, Edmund A. Rossi⁴, Michele J. Losman¹, Pierre-Yves Brard³, Chien-Hsing Chang¹^,4, Steven M. Larson⁵ and David M. Goldenberg¹^,3^,4

¹ Immunomedics, Inc., Morris Plains, New Jersey; ² Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York; ³ Center for Molecular Medicine and Immunology, Belleville, New Jersey; ⁴ IBC Pharmaceuticals, Inc., Morris Plains, New Jersey; and ⁵ Nuclear Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York

View larger version (21K):

[in a new window]

FIGURE 1. RP-HPLC illustrates final radiolabeled products obtained under different radioiodination conditions. (A and C) ¹²⁴I-Labeled products obtained using Na¹²⁴I with (C) or without (A) addition of carrier-added iodide. Addition of carrier improved yields, with formation of both mono- and diiododinated forms. (B and D) ¹³¹I-Labeled products prepared using IODO-GEN–coated vials vs. microparticulate IODO-GEN. UnB = unbound radioiodine.

View larger version (49K):

[in a new window]

FIGURE 2. Whole-body ${gamma}$ -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.

View larger version (35K):

[in a new window]

FIGURE 3. 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.

View larger version (32K):

[in a new window]

FIGURE 4. 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.

View larger version (63K):

[in a new window]

FIGURE 5. Focus 120 microPET images of animals bearing LS174T human colorectal cancer xenografts 1.7 h after ¹⁸F-FDG. All images were taken at same maximum intensity and background set to 0.0. (A) Photographs of 3 tumor-bearing animals. (B) Coronal slice (0.82-mm thick) taken to highlight uptake in tumor (arrows), as well as in bone marrow (BM) of shoulder and in hind quarters. Heart (H) and brain can also be seen in some images. Bars represent planes used for transverse and sagittal sections. (C) Transverse sections that highlight tumor or heart wall uptake. Sagittal sections illustrate the side view of tumor (D) and a plane that highlights heart, bone marrow, and urinary bladder (UB) activity (E). Tumor weights were 0.425, 0.321, and 0.153 g, respectively.