The purpose of this research was to optimize chemical parameters to radiolabel antibody fragments and other biologics with Tc-99m for scintigraphic detection of tumors. Tc-99m is the optimal radionuclide used for scintigraphic imaging but Tc99m labeled biologics have not been actively used mainly because of complexity of Tc-99m chemistry. We have taken a bifunctional chelate approach which involved the synthesis of a bifunctional chelator (BFC), conjugation of the BFC to biologics and radiolabeling of the chelator moiety with Tc-99m. We have selected mercaptoacetyltriglycine (MAG3) as the BFC agent because it binds Tc-99m strongly forming a square pyramid structure used as a renal imaging agent. To use MAG3 as a BFC, we had to overcome two major obstacles. One was related to the chemistry of mercapto group. The mercapto group is known to be the best ligand for binding Tc-99m. However, it is also one of the most chemically reactive groups. As a result, we had to find a right protecting group which protects the mercapto group from undergoing chemical reactions during storage but is readily de- protected under a mild condition. The second problem was related to Tc-99m chemistry. Technetium-99m available from a Tc-99m generator is in the form of Tc-99m pertechnetate which is chemically non-reactive and has to be reduced to an oxidation state of +5 for binding with MAG3. This reduced Tc-99m is very reactive and can undergo various reactions such as reoxidation to Tc-99m pertechnetate, binding with proteins non-specifically, and hydrolysis reaction to Tc-99m colloids if no chelating agent is present. Therefore, a transchelating agent had to be selected to hold both the reduced Tc-99m and stannous ion (reducing agent) in a soluble form but transfer Tc-99m to MAG3 when the mercapto group of MAG3 is generated. Using a benzoyl group as a mercapto protecting group and tricine as a transchelating agent, we have successfully labeled Bz-MAG3 conjugated antibody Fab and a single chain Fv from Dr. Ira Pastan with Tc-99m with a 50% labeling yield. The immunoreactivity and specificity of the labeled fragments will be determined in the near future.

Agency
National Institute of Health (NIH)
Institute
Clinical Center (CLC)
Type
Intramural Research (Z01)
Project #
1Z01CL002001-01
Application #
3752226
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
1
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Clinical Center
Department
Type
DUNS #
City
State
Country
United States
Zip Code
Chakraborty, Mala; Wansley, Elizabeth K; Carrasquillo, Jorge A et al. (2008) The use of chelated radionuclide (samarium-153-ethylenediaminetetramethylenephosphonate) to modulate phenotype of tumor cells and enhance T cell-mediated killing. Clin Cancer Res 14:4241-9
Chakraborty, Mala; Gelbard, Alexander; Carrasquillo, Jorge A et al. (2008) Use of radiolabeled monoclonal antibody to enhance vaccine-mediated antitumor effects. Cancer Immunol Immunother 57:1173-83
Khaibullina, Alfia; Jang, Beom-Su; Sun, Haihao et al. (2008) Pulsed high-intensity focused ultrasound enhances uptake of radiolabeled monoclonal antibody to human epidermoid tumor in nude mice. J Nucl Med 49:295-302
Barrett, Tristan; Koyama, Yoshinori; Hama, Yukihiro et al. (2007) In vivo diagnosis of epidermal growth factor receptor expression using molecular imaging with a cocktail of optically labeled monoclonal antibodies. Clin Cancer Res 13:6639-48
Hama, Yukihiro; Urano, Yasuteru; Koyama, Yoshinori et al. (2007) A target cell-specific activatable fluorescence probe for in vivo molecular imaging of cancer based on a self-quenched avidin-rhodamine conjugate. Cancer Res 67:2791-9
Zhang, YuJian; Xiang, Laiman; Hassan, Raffit et al. (2006) Synergistic antitumor activity of taxol and immunotoxin SS1P in tumor-bearing mice. Clin Cancer Res 12:4695-701
Zhang, Meili; Yao, Zhengsheng; Zhang, Zhuo et al. (2006) The anti-CD25 monoclonal antibody 7G7/B6, armed with the alpha-emitter 211At, provides effective radioimmunotherapy for a murine model of leukemia. Cancer Res 66:8227-32
Dadachova, E; Park, C; Eberly, N et al. (2001) In vitro and in vivo characterization of 67Ga(3+) complexes with cis,cis-1,3,5-triamino-cyclohexane-N,N',N""-triacetic acid derivatives. Nucl Med Biol 28:695-701
Yao, Z; Garmestani, K; Wong, K J et al. (2001) Comparative cellular catabolism and retention of astatine-, bismuth-, and lead-radiolabeled internalizing monoclonal antibody. J Nucl Med 42:1538-44
Karamychev, V N; Panyutin, I G; Kim, M K et al. (2000) DNA cleavage by 111In-labeled oligodeoxyribonucleotides. J Nucl Med 41:1093-101

Showing the most recent 10 out of 14 publications