The synthesis and in vitro evaluation of a 99mtechnetium-nitroimidazole complex based on a bis(amine-phenol) ligand: comparison to BMS-181321

Abstract

We have developed a 99mTechnetium complex for imaging of hypoxic tissue (BMS-181321). Recently, another nitroimidazole derivative, based upon a bis(amine-phenol) ligand, was described in the patent literature. To compare this compound to BMS-181321, we have synthesized the ligand, prepared its 99mTc complex, and evaluated its performance in two in vitro assays of bioefficacy: membrane permeability and uptake in normoxic and anoxic cardiocytes. In attempting to reproduce the synthesis of the ligand described in the patent application, we found that one intermediate could not be made by the method described, and alternative routes were investigated. Complexation of the bis(amine-phenol) nitroimidazole with 99mTc gave an apparent single complex; this appeared as a broad peak on HPLC analysis. Purification by a solid-phase method gave a complex with 95% radiochemical purity. This complex was not permeable to cultured bovine brain endothelial cells nor did it show preferential uptake in anoxic myocytes.