Towards developing a Non-SnCl2 formulation for RP444, a new radiopharmaceutical for thrombus imaging

There are many factors influencing the yield and radiochemical purity (RCP) of the radiopharmaceutical RP444. These include heating temperature, heati ng time, pH, the use of a buffering agent and a bulking agent, as well as t he component (XV066, tricine, TPPTS, and (NaTcO4)-Tc-99m) concentration. Th rough a series of radiolabeling experiments, we found that a formulation co mprised of 20 mug of XV066, 6.5 mg of tricine, 40 mg of mannitol, 5 mg of T PPTS, and 0.1 mg of Pluronic acid dissolved in 1.0 mt of 250 mM succinate b uffer (pH 5.0) gives the best RCP for RP444. The formulation can be lyophil ized to form a stable crystal "cake". The radiolabeling is achieved by addi ng 1.5 mL generator eluant (33-133 mCi of (NaTcO4)-Tc-99m) to a lyophilized vial and heating the reaction mixture at 100 degreesC for 10 min. Using th is formulation, RP444 is prepared consistently in high yield with RCP great er than or equal to 90%. Formation of [Tc-99m]colloid is minimal (<0.5%). ( C) 2001 Wiley-Liss, Inc.