Synthesis, radiolabeling, and preliminary evaluation in mice of some (N-diethylaminoethyl)-4-iodobenzamide derivatives as melanoma imaging agents.

N-(2-Diethylaminoethyl)-4-iodobenzamide (BZA) is a radiopharmaceutical recently developed in our laboratory for the scintigraphic detection of melanoma and metastases. Optimal time for imaging was between 18-24 h p.i. of [123I] BZA. With a view to selecting compounds able to provide quality images shortly after the injection, synthesis of an initial series of BZA derivatives and their evaluation in B16 melanoma bearing mice have been carried out. The [125I] radiolabeled products were obtained by a simple isotopic exchange procedure with high radiochemical yields (85-95%). After i.v. administration of the compounds we observed a good tumoral targeting ability. Tumoral activity peaked at 2.6 to 7.70% injected dose per g within 1 h post-injection. One of the benzamides with a blood clearance faster than that of BZA--0.06 vs. 0.2% I D/g--6 h p.i. gave the same tumor to blood and to organ ratios as BZA at 12-18 h p.i. Based on these preclinical data we hope to obtain good tumoral images 6 h p.i. in scintigraphic studies in man.