HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Griffiths, G. L. Articles by Goldenberg, D. M. Search for Related Content PubMed PubMed Citation Articles by Griffiths, G. L. Articles by Goldenberg, D. M.

Reagents and Methods for PET Using Bispecific Antibody Pretargeting and ⁶⁸Ga-Radiolabeled Bivalent Hapten-Peptide-Chelate Conjugates

¹ Immunomedics, Inc., Morris Plains, New Jersey; IBC Pharmaceuticals, Inc., Morris Plains, New Jersey
² Garden State Cancer Center, Belleville, New Jersey

The aim of this work was to develop reagents and methods potentially useful in PET, using ⁶⁸Ga in a 2-step pretargeting protocol. Methods: We prepared bispecific antibodies (bsAbs) for disease-specific targeting of carcinoembryonic antigen-positive cells and recognition of later-administered bivalent hapten-peptide conjugates. The secondary antibody arm (antibody 679) recognizes a histaminyl-succinyl-glycine (HSG) structural subunit. The bsAbs were prepared as Fab' x Fab' conjugates using chemical cross-linking methods and as bispecific diabodies using recombinant DNA technologies. A HSG-bivalent hapten conjugate bearing the macrocyclic ring chelating agent 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) was designed to be readily radiolabeled with ⁶⁸Ga taken directly from a ⁶⁸Ge/⁶⁸Ga generator system. Reagents were tested in vitro and, then, for their targeting properties in a preclinical animal model of human cancer. Results: A chemically cross-linked hMN-14 x 679 F(ab')₂ and a fully humanized bispecific diabody construct (BS1.5H), expressed in Escherichia coli, were prepared for this work. We synthesized the bivalent peptide termed IMP 241 [DOTA-Phe-Lys(HSG)-D-Tyr-Lys(HSG)-NH₂] and labeled it with ⁶⁸Ga and ⁶⁷Ga at temperatures from 45°C to 100°C, over times of 15 min to 1 h, establishing 15 min at 95°C as a useful condition for ⁶⁸Ga labeling. When we formulated the IMP 241 bivalent hapten-peptide with ammonium acetate buffer at pH 4–5 and eluted the ⁶⁸Ga from the generator directly into the peptide solution, we achieved an almost quantitative incorporation of the ⁶⁸Ga into IMP 241, as analyzed by size-exclusion high-performance liquid chromatography, after mixing the complex with the 679 antibody. For in vivo studies we used ⁶⁷Ga-IMP 241 as a surrogate for ⁶⁸Ga-IMP 241, in view of the short, 68-min half-life of the ⁶⁸Ga nuclide. The ⁶⁷Ga-IMP 241 was successfully pretargeted to human colon tumor xenografts in athymic mice with both the chemical and the diabody bispecific proteins. High tumor-to-normal tissue ratios for ⁶⁷Ga uptake were found for all tissues at 1 to 6 h after injection of ⁶⁷Ga-IMP 241. When using the BS1.5H diabody for pretargeting, tumor-to-blood, tumor-to-liver, and tumor-to-lung ratios of ⁶⁷Ga-IMP 241 at 1 and 3 h after injection were 41:1 and 137:1, 51:1 and 106:1, and 16:1 and 46:1, respectively. Conclusion: The general approach described, along with the new compositions and the labeling methods we have developed, may eventually allow for use of ⁶⁸Ga-labeled specific targeting agents in a routine clinical PET application.

Key Words: ⁶⁸Ga • ⁶⁷Ga • PET • bispecific antibodies • 2-step pretargeting

This article has been cited by other articles:

				G. A.M.S. van Dongen, G. W.M. Visser, M. N. Lub-de Hooge, E. G. de Vries, and L. R. Perk Immuno-PET: A Navigator in Monoclonal Antibody Development and Applications Oncologist, December 1, 2007; 12(12): 1379 - 1389. [Abstract] [Full Text] [PDF]

				R. M. Sharkey, H. Karacay, W. J. McBride, E. A. Rossi, C.-H. Chang, and D. M. Goldenberg Bispecific Antibody Pretargeting of Radionuclides for Immuno Single-Photon Emission Computed Tomography and Immuno Positron Emission Tomography Molecular Imaging: An Update Clin. Cancer Res., September 15, 2007; 13(18): 5577s - 5585s. [Abstract] [Full Text] [PDF]

				W. J. McBride, P. Zanzonico, R. M. Sharkey, C. Noren, H. Karacay, E. A. Rossi, M. J. Losman, P.-Y. Brard, C.-H. Chang, S. M. Larson, et al. Bispecific Antibody Pretargeting PET (ImmunoPET) with an 124I-Labeled Hapten-Peptide J. Nucl. Med., October 1, 2006; 47(10): 1678 - 1688. [Abstract] [Full Text] [PDF]

				D. M. Goldenberg, R. M. Sharkey, G. Paganelli, J. Barbet, and J.-F. Chatal Antibody Pretargeting Advances Cancer Radioimmunodetection and Radioimmunotherapy J. Clin. Oncol., February 10, 2006; 24(5): 823 - 834. [Abstract] [Full Text] [PDF]

				R. M. Sharkey, H. Karacay, T. M. Cardillo, C.-H. Chang, W. J. McBride, E. A. Rossi, I. D. Horak, and D. M. Goldenberg Improving the Delivery of Radionuclides for Imaging and Therapy of Cancer Using Pretargeting Methods Clin. Cancer Res., October 1, 2005; 11(19): 7109s - 7121s. [Abstract] [Full Text] [PDF]

				H. R. Maecke, M. Hofmann, and U. Haberkorn 68Ga-Labeled Peptides in Tumor Imaging J. Nucl. Med., January 1, 2005; 46(1_suppl): 172S - 178S. [Abstract] [Full Text] [PDF]