Synthesis and in vivo evaluation of ortho-[124I]iodohippurate for PET renography in healthy rats

Abstract

Ortho-[131I]iodohippurate [131I]OIH (marketed as Hippuran I 131), a gold standard for radionuclide renography, and [123I]OIH were in clinical use for decades. Here we radiolabeled OIH with 124I (a positron emitter) to combine the desirable biological properties of OIH and to enable the use of positron emission tomography (PET) for renography. [124I]OIH was synthesized with a slight modification to a previously reported method for the kit preparation of [123I]OIH based on the Cu(II) catalyzed isotope-exchange reaction. Our method utilized heating at 120°C under sealed condition in a heating block instead of autoclaving. [124I]OIH was obtained with a radiochemical purity of >99.3%, radiochemical yield of 94.5%, and specific activity of ~17 MBq/mg. Biodistribution studies in healthy Sprague Dawley rats revealed results comparable to that of [131I]OIH as reported in the literature. The PET-derived [124I]OIH renograms revealed an average time-to-peak of 2.8±0.4min and the average time-to-half-maximal activity of 11.4±1.5min, which are also comparable to that of [131I]OIH as reported in the literature. Results from this study indicate that the synthesis of [124I]OIH without using an autoclave and [124I]OIH PET renography are feasible.