Technetium-99m-labeled monoclonal antibodies: Influence of technetium-99m binding sites

Journal Article · Sun May 01 04:00:00 EDT 1994 · Journal of Nuclear Medicine

OSTI ID:95913

John, E; Thakur, M L; Wilder, S; Alauddin, M M; Epstein, A L ^[1]

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1. Thomas Jefferson Univ. Hospital, Philadelphia, PA (United States)

A number of {sup 99m}Tc-labeled monclonal antibodies (Mabs) are being evaluated for diagnostic applications. Preparations are carried out using both direct and indirect (bifunctional chelating agent, BFCA) labeling procedures in which nonspecific {sup 99m}Tc binding has been postulated. By using the ascorbic acid (AA) reduction-mediated direct labeling procedure and diaminotetrathiol (N{sub 2}S{sub 4}) as a BFCA method, the authors examined the role of specific binding sites and aliphatic E amino groups of lysine as nonspecific binding sites for {sup 99m}Tc. Labeling yields for the direct and N{sub 2}S{sub 4} {open_quotes}regular{close_quotes} preparations averaged 73% {+-} 2.8% and 91% {+-} 2%, for the {open_quotes}specific{close_quotes} preparations, 60% {+-} 3.5% and 75% {+-} 2%, and for the {open_quotes}nonspecific{close_quotes} preparations 13% {+-} 1.0% and 16% {+-} 1% respectively. All preparations were evaluated in tumor-bearing mice. The control and specific preparations permitted excellent scintigraphic visualization of tumors; the percentages of specific preparations in the tumors being 2.1% {+-} 0.5% and 3.1% {+-} 0.4%, respectively. With nonspecific preparations, tumors were not visualized and the percentages of administered radioactivity per gram of tumor were only 0.9% {+-} 0.2% and 0.9% {+-} 0.3%, respectively. In these {sup 99m}Tc labeling procedures, the amino group-mediated nonspecific binding of {sup 99m}Tc to Mabs can be as high as 16% and contributes to increased liver uptake and decreased tumor uptake of radioactivity. 31 refs., 4 figs., 3 tabs.

• DOE Contract Number: FG02-92ER61485
• OSTI ID: 95913
• Journal Information: Journal of Nuclear Medicine, Journal Name: Journal of Nuclear Medicine Journal Issue: 5 Vol. 35; ISSN JNMEAQ; ISSN 0161-5505
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
CHEMICAL PREPARATION
LABELLING
MONOCLONAL ANTIBODIES
RADIOPHARMACEUTICALS
TECHNETIUM 99