Immunomedics Inc announced the recent issuance of U.S. patent 6,558,669 covering the Company's proprietary method of labeling antibodies with Iodine-131. The technology underlying this new labeling method, which has been demonstrated in pre-clinical trials to result in a more stable antibody conjugate, involves the attachment of the radioisotope to a peptide that comprises at least one binding site for radioiodine, which in turn can be linked directly to the antibody.

Cynthia L. Sullivan, President and Chief Executive Officer of Immunomedics, explained: "I-131 continues to be a very useful isotope in nuclear medicine, having been used to successfully treat thyroid cancers for the last 50 years. In the early development of isotopes linked to antibodies for the treatment of cancer, I-131 was initially of major interest, but its use declined as more stable methods were developed for linking other isotopes, such as yttrium-90. These early methods of attaching I-131 were unstable, resulting in premature degradation of the radioiodine in the body and clearance of the isotope through the kidneys and urine, thus exposing the patient and environment to increased levels of radioactivity."

"With our new labeling method, the radioiodine is retained for longer periods by the antibody, and based upon our initial animal studies, we believe the I-131 remains in the tumor for the time needed to be efficacious. In fact, in pre-clinical trials involving human lung cancer growing in mice, markedly improved targeting and therapy were achieved with this new method, as compared to using the conventional radiolabeling method," she added.

Sullivan added: "Conventional therapeutic treatments using I-131 typically require individualized patient dosing, because the isotope detaches quickly and distributes differently among patients. We believe this will not be the case with our new I-131 labeling method, which we now hope to confirm in clinical trials involving patients with cancer. We are now planning clinical trials with I-131 conjugated by this method to an antibody that targets colorectal cancer."