Synthesis and formulation of [⁶⁴Cu]Cu-PTSM for PET perfusion imaging in small animal models

Purpose: The [⁶⁴Cu]Cu-PTSM radiopharmaceutical, pyruvaldehyde bis(N⁴-methylthiosemicarbazonato)copper(II), is suitable for use in microPET and autoradiographic imaging to assess regional tissue perfusion in small animal models. We report here an approach to synthesis and formulation of the [⁶⁴Cu]Cu-PTSM radiopharmaceutical at the high concentrations required for use in imaging with rodent models of human disease.

Methods: The [⁶⁴Cu]Cu-PTSM radiopharmaceutical was prepared at small volumes by addition of the H₂PTSM ligand to acetate-buffered [⁶⁴Cu]copper chloride, followed by solid phase extraction to isolate and purify the product, which was then recovered and formulated in 2-mL normal saline containing 5% ethanol and 5% propylene glycol.

Results: The [⁶⁴Cu]Cu-PTSM radiopharmaceutical has been produced over the range of 0.41-1.85 GBq (11-50 mCi) [⁶⁴Cu]Cu-PTSM in the 2.0-mL final product volume. Radiochemical purity of the [⁶⁴Cu]Cu-PTSM radiopharmaceutical product averaged 99.8 ± 0.4% (n = 64), with the final formulated product produced at an 83 ± 5% radiochemical yield.

Conclusions: The approach to [⁶⁴Cu]Cu-PTSM synthesis and formulation has proven to be reliable and robust, supporting radiopharmaceutical delivery at the high concentrations required for PET studies in mouse and other rodent models.