Purification and biological evaluation of radioiodinated clozapine as possible brain imaging agent

A method for the preparation of high radiochemical yield 125 I-clozapine was developed in order to characterize the binding properties of serotonergic and dopaminergic receptors. This labeling reaction was done by electrophilic substitution giving two radioiodinated products. The major radiolabeled product with a yield reached 91.4 %, and the minor one with a yield 8 %. Different chromatographic techniques (electrophoresis and HPLC) were used to evaluate the radiochemical yield and purity of the labeled products. Biodistribution results indicate that the radioiodo-clozapine cross the blood brain barrier with maximum uptake (10.5 ± 0.4 % injected dose/g tissue at 60 min) and high retention (4.0 ± 0.2 % injected dose/g tissue at 120 min). Brain uptake and retention of 125 I-clozapine is higher than that of currently used radiopharmaceuticals for brain imaging.