Development of 111In-labeled porphyrins for SPECT imaging

Objectives: The aim of this research was the development of 111In-labeled porphyrins as possible radiopharmaceuticals for the imaging of tumors. Methods: Ligands, 5, 10, 15, 20-tetrakis (3, 5-dihydroxyphenyl) porphyrin) (TDHPP), 5, 10, 15, 20-tetrakis (4-hydroxyphenyl) porphyrin (THPP) and 5, 10, 15, 20-tetrakis (3,4-dimethoxyphenyl) porphyrin) (TDMPP) were labeled with 111InCl3 (produced from proton bombardment of natCd target) in 60 min at 80ºC. Quality control of labeled compounds was performed via RTLC and HPLC followed by stability studies in final formulation and presence of human serum at 37ºC for 48 h as well as partition coefficient determination. The biodistribution studies performed using tissue dissection and SPECT imaging up to 24h. Results: The complexes were prepared with >99% radiochemical purity (HPLC and RTLC), high stability in 48h. Partition coefficients (calculated as log P) for 111In-TDHPP, 111In-THPP and 111In-TDMPP were 0.88, 0.8 and 1.63 respectively. Conclusion: Due to urinary excretion with fast clearance for 111In-TDMPP, this complex is probably a suitable candidate for considering as a possible tumor imaging agent.