Nuclear medicine program progress report for quarter ending March 31, 1995

In this report the conditions for ``direct`` labeling of the anti-granulocyte (MAb) BW 250/183 monoclonal antibody with rhenium-188 (Re-188) from a generator are described. Re-188-BW 250/183 is of interest for potential use for bone marrow ablation. The labeling time, temperature, pH, and the amount of tin and citric acid were optimized utilizing IgG. Radiolabeling yields of greater than 97% were achieved using 1 mL of a phthalate/tartrate buffer (pH 5.{und M}=?), 250 {micro} g BW 250/183, 1.0 mg citric acid, 400 {micro} g tin (II) chloride, and 1 mL of the tungsten-188/rhenium-188 generator eluent (200--800 {micro} Ci of Re-188). Analysis of the Re-188-labeled IgG and BW 250/183 was performed by Instant Thin Layer Chromatography (ITLC), Sephadex purification and High Performance Liquid Chromatography (HPLC). When the labeling was performed at room temperature or 37 C, in vitro stability studies performed in HSA solution, cysteine solution, 6 {und M} urea solution and a 1% casein solution showed that the Re-188 label demonstrated a similar stability profile in all solutions. Initial studies indicate that Re-188-BW 250/183 retained {approximately} 90% of immunoreactivity when compared to the technetium-99m labeled antibody prepared from the same kit. During this period, several radioisotopes prepared in the ORNL HFIR were also supplied on a cost-recovery basis or provided to collaborators for ongoing collaborative projects. These include tin-117m, processed tungsten-188 and the ORNL alumina-based tungsten-188/rhenium-188 generators.