Towards Developing A Non‐SnCl2 Formulation for RP444, A New Radiopharmaceutical for Thrombus Imaging

Abstract

There are many factors influencing the yield and radiochemical purity (RCP) of the radiopharmaceutical RP444. These include heating temperature, heating time, pH, the use of a buffering agent and a bulking agent, as well as the component (XV066, tricine, TPPTS, and Na99mTcO4) concentration. Through a series of radiolabeling experiments, we found that a formulation comprised of 20 μg of XV066, 6.5 mg of tricine, 40 mg of mannitol, 5 mg of TPPTS, and 0.1 mg of Pluronic acid dissolved in 1.0 mL of 250 mM succinate buffer (pH 5.0) gives the best RCP for RP444. The formulation can be lyophilized to form a stable crystal “cake”. The radiolabeling is achieved by adding 1.5 mL generator eluant (33–133 mCi of Na99mTcO4) to a lyophilized vial and heating the reaction mixture at 100°C for 10 min. Using this formulation, RP444 is prepared consistently in high yield with RCP ≥ 90%. Formation of [99mTc]colloid is minimal (< 0.5%). © 2001 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:114–123, 2001