PREPARATION OF A PURE TC-99M-F(AB')(2) RADIOIMMUNOCONJUGATE BY DIRECT LABELING METHODS

Intact IgG and Fab' can be labeled directly with Tc-99m to give quantitative incorporation of radioactivity into the protein. With F(ab')(2) the reductive conditions yield a mixture of Tc-99m-F(ab')(2) and Tc-99m-Fab'. We now report a direct labeling method to produce only Tc-99m-F(ab')(2) in quantitative yield and contaminated with Tc-99m-Fab'. The properties, stability and biodistribution of the Tc-99m-F(ab')(2) have been compared to Tc-99m-Fab'. This new technology will allow us to compare technetium direct-labeled IgG, F(ab')(2) and Fab' derivatives of the same antibody for radioimmunodetection.