The long range objectives of this proposal are to prepare radiolabeled antibodies that are tumor specific and organ non-specific for cancer diagnosis and therapy. To achieve these objectives an indirect approach will be used to radiolabel antibodies with 111-In, 99mTc, and 90-Y. The indirect approach consists of three steps. Bifunctional chelating agents are first synthesized. These chelators are then conjugated to antibodies. The chelators are radiolabeled with the metallic radionuclides either prior to or after the conjugation to antibodies. DTPA analogues will be used as bifunctional chelators because DTPA was reported to make stable complexes with various metallic ions. Once antibodies are radiolabeled through the above steps, the chemical stability of the radiolabeled antibodies will be tested by incubating the serum in vitro. The immunoreactivity will be determined by affinity binding assays. The labeled antibody will then be injected into mice or rats with tumor xenografts or pharmacokinetic studies and imaging. A successful radioimmunoimaging or therapy is mainly determined by a relative term, a tumor to background ratio. The maximum tumor uptake was reported to take place within 1 or 2 days postinjection of 111-In or 131I labeled antibodies and 6 hrs postinjection of the radiolabeled Fab fragments. However, successful radioimmunoimaging of tumor was achieved 2 to 7 days postinjection even though the time of maximum tumor concentration has passed and background activity persists. The limiting factor for 111-In and 99mTc labeled antibodies as successful tumor imaging agents was reported to be high activities in liver. spleen and kidney (especially for F(ab')2 and Fab fragments). The major aim of this proposal is to minimize the background activities. To achieve this goal, 1) we propose to develop reliable chemical methods to conjugate DTPA analogues to antibodies which result in minimum deactivation of immunoreactivity and optimum clearance from, blood, liver and kidney. We will place a spacer with a chemical bond, less stable than a peptide bond, between DTPA and antibody. 2) We will optimize conditions for radiolabeling the antibody DTPA conjugates with 111-In, 99mTc and 90-Y. 3) We will develop analytical methods to separate immunoreactive antibody from irrelevant or deactivated antibody. 4) We will investigate a system to amplify a tumor to background ratio. 5) We will investigate the effects of pharmacokinetic parameters such as antibody concentration, antigen concentration (or tumor size) and circulating antigen on the tumor to background ratio.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA028462-07
Application #
3168145
Study Section
Experimental Immunology Study Section (EI)
Project Start
1986-04-01
Project End
1990-03-31
Budget Start
1987-04-01
Budget End
1988-03-31
Support Year
7
Fiscal Year
1987
Total Cost
Indirect Cost
Name
George Washington University
Department
Type
Schools of Medicine
DUNS #
City
Washington
State
DC
Country
United States
Zip Code
20052
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Yokoyama, K; Reynolds, J C; Paik, C H et al. (1990) Immunoreactivity affects the biodistribution and tumor targeting of radiolabeled anti-P97 Fab fragment. J Nucl Med 31:202-10
Quadri, S M; Paik, C H; Reba, R C et al. (1990) Optimization of biodistribution by introducing different chemical linkages between antibody and an indium-111 chelate. Cancer Treat Res 51:201-13
Paik, C H; Quadri, S M; Reba, R C (1989) Interposition of different chemical linkages between antibody and 111In-DTPA to accelerate clearance from non-target organs and blood. Int J Rad Appl Instrum B 16:475-81
Paik, C H; Yokoyama, K; Reynolds, J C et al. (1989) Reduction of background activities by introduction of a diester linkage between antibody and a chelate in radioimmunodetection of tumor. J Nucl Med 30:1693-701
Herlyn, D; Powe, J; Munz, D L et al. (1986) Radioimmunodetection of human tumor xenografts by monoclonal antibody F(ab')2 fragments. Int J Rad Appl Instrum B 13:401-5
Paik, C H; Eckelman, W C; Reba, R C (1986) Transchelation of 99mTc from low affinity sites to high affinity sites of antibody. Int J Rad Appl Instrum B 13:359-62
Paik, C H; Phan, L N; Hong, J J et al. (1985) The labeling of high affinity sites of antibodies with 99mTc. Int J Nucl Med Biol 12:3-8
Paik, C H; Hong, J J; Ebbert, M A et al. (1985) Relative reactivity of DTPA, immunoreactive antibody-DTPA conjugates, and nonimmunoreactive antibody-DTPA conjugates toward indium-111. J Nucl Med 26:482-7