June 18, 2009 (FinancialWire) — Immunomedics, Inc. (NASDAQ: IMMU) reported that TF2, a proprietary pretargeting antibody, produced tumor-specific PET imaging and prolonged survival in a human colorectal cancer model. Results from two studies were presented at the 56th annual meeting of the Society of Nuclear Medicine.

TF2 is an antibody constructed using the company’s proprietary protein engineering platform technology, called Dock-and-Lock . It specifically targets the carcinoembryonic (CEA or CEACAM5) antigen expressed in many human cancers, including colorectal cancer. Unlike conventional antibodies which can only attach to one receptor, TF2 has been modified to contain an additional binding site that recognizes a radioisotope-carrying peptide. This allows the separate administration of TF2 before the delivery of radioisotope, a concept known as pretargeting, which is developed by the company’s majority-owned subsidiary, IBC Pharmaceuticals, Inc.

Pretargeting with TF2 has been shown to improve PET imaging of colorectal cancer in animals. (For more information, please refer to the company’s earlier press release at www.immunomedics.com/news_pdf/2008_PDF/PR06162008.pdf). The first study reported at the meeting examined the selectivity and specificity of TF2 compared with F-18 FDG in PET imaging of colorectal cancer. The therapeutic efficacy of TF2 against colorectal cancer was assessed in the second study using an animal model.

F-18 FDG is a sugar analog approved for use in the U.S. for the detection of certain tumors, coronary artery disease, and epilepsy. It is the most widely used radiopharmaceutical in PET to determine abnormal glucose metabolism. However, F-18 FDG uptake is also accelerated during inflammatory processes and in rapidly-proliferating normal cells, which may lead to false-positive results and lower specificity.

For the imaging study, animals carrying human colorectal tumor and with chemically-induced inflamed muscle were imaged with either F-18 FDG or TF2 and a radiolabeled peptide. In the TF2 group of animals, uptake of radioactivity was more than 10-fold higher in the tumor than in the inflamed muscle. The levels in normal organs and tissues were all significantly lower. With 18F-FDG, both the tumor and the inflamed muscle were clearly visualized at 1 hour.

In the therapeutic study, treatment with 1 cycle of TF2 and a radiolabeled peptide significantly prolonged median survival time of animals injected with human colorectal cancer cells to 24 days compared with 13 days from the untreated group. Moreover, 2 and 3 cycles of TF2 treatments extended MST to 45 and 65 days, respectively. Bone marrow and kidney toxicity to the TF2 group was minimal. For the first time, therefore, fractionated dosing of pretargeted radioimmunotherapy was found to be superior in efficacy over single-cycle RAIT.

Immunomedics is a New Jersey-based biopharmaceutical company primarily focused on the development of monoclonal, antibody-based products for the targeted treatment of cancer, autoimmune and other serious diseases.

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