Radioiodinated azomycin pyranoside (IAZP): a novel non-invasive marker for the assessment of tumor hypoxia.

1-(4-Iodo-4-deoxy-beta-L-xylopyranosyl)-2-nitroimidazole (Iodoazomycin Pyranoside; IAZP) was synthesized, labelled with radioiodine(123I, 125I) and evaluated for non-invasive assessment of tumor hypoxia. A biodistribution study with Balb/c mice bearing EMT-6 tumors showed a tumor-to-blood ratio of 13.9, representing 0.5 percent of injected dose per gram of tissue, at 24 hours post injection. This ratio is the highest for any 2-nitro-imidazole reported to date in this tumor model. Rapid elimination of radioactivity from the whole-body was noted (greater than 97% in 24 hours) and thyroid radioactivity at 24 hours was much lower than with other analogues of this series. No toxicity was observed in Balb/c mice at a dose 100 times higher than the anticipated human dose required for scintigraphic imaging. Planar, whole-body gamma scintigraphic images in the murine Balb/c EMT-6 tumor model clearly delineated tumor tissue at 24 hours post injection. These observations suggest that IAZP may be a suitable agent for non-invasive, clinical assessment of tumor hypoxia.