Immunomedics Creates Novel Cytokine Immunoconjugates Using Dock-and-Lock

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| Source: Immunomedics, Inc.

SAN DIEGO, April 16, 2008 (PRIME NEWSWIRE) -- Immunomedics, Inc. (Nasdaq:IMMU), a biopharmaceutical company focused on developing monoclonal antibodies to treat cancer and other serious diseases, announced today at the 2008 Annual Meeting of AACR in San Diego, CA, the development of new cytokine-antibody conjugates using the Company's and its subsidiary, IBC Pharmaceuticals, Inc.'s proprietary Dock-and-Lock method (DNL).

DNL employs two building units: the dimerization and docking domain (DDD) module and the anchoring domain (AD) module for the creation of protein complexes. In this study, three cytokines: erythropoietin (EPO), granulocyte-colony stimulating factor (G-CSF) and interferon-alpha-2b (IFN alpha 2b) were selected to produce the DDD modules. Each DDD module contains two copies of the cytokine. Separately, AD modules were derived from five of the Company's proprietary humanized antibodies: epratuzumab (anti-CD22), veltuzumab (anti-CD20), hL243 (anti-HLA-DR), h734 (anti-indium-DTPA) and an antibody to an undisclosed target. Each antibody-AD module possesses two copies of the anchoring domain, and as such can anchor two cytokine-DDD modules.

When combined, the two modules interact with each other exclusively in a predictable and quantitative manner to produce a complex that has four copies of a cytokine anchored onto a humanized antibody. As exemplified by the veltuzumab-IFN alpha 2b complex, these novel antibody-based cytokines each retained the biological functions of its parental cytokine in vitro, with pharmacokinetic and targeting properties in mice comparable to the humanized antibodies selected.

"We believe these results demonstrate that DNL offers a modular approach to efficiently tether cytokines onto a targeting antibody, and we anticipate these new compounds will have a higher in vivo potency than the original cytokines due to improved pharmacokinetics and reduced systemic toxicity," remarked Cynthia L. Sullivan, President and CEO. "This initial success we believe supports our contention that DNL represents a new platform technology for creating novel classes of biological therapeutics, including improvements of existing products," she added.

The Company has previously created two DNL-PEGylated IFNa2b molecules by site-specifically conjugating a large molecule called polyethylene glycol (PEG) to IFNa2b using DNL (please refer to http://www.immunomedics.com/news_pdf/2007_PDF/PR12102007b.pdf ).

About the Dock and Lock Method (DNL)

DNL is a platform technology that utilizes the natural interaction between two proteins, cyclic AMP-dependent protein kinase (PKA) and A-kinase anchoring proteins (AKAPs). The region that is involved in such interaction for PKA is called the dimerization and docking domain (DDD), which always appears in pairs. Its binding partner in AKAPs is the anchoring domain (AD). When mixed together, DDD and AD will bind with each other spontaneously to form a binary complex, a process termed docking. Once "docked," certain amino acid residues incorporated into DDD and AD will react with each other to "lock" them into a stably tethered structure. The outcome of the DNL method is the exclusive generation of a stable complex, in a quantitative manner that retains the full biological activities of its individual components. Diverse drugs, chemical polymers, proteins, peptides, and nucleic acids are among suitable components that can be linked to either DDD or AD. Since DDD always appears in pairs, any component that is linked to DDD will have two copies present in the final products.

About Immunomedics

Immunomedics is a New Jersey-based biopharmaceutical company focused on the development of monoclonal, antibody-based products for the targeted treatment of cancer, autoimmune and other serious diseases. We have developed a number of advanced proprietary technologies that allow us to create humanized antibodies that can be used either alone in unlabeled or "naked" form, or conjugated with radioactive isotopes, chemotherapeutics or toxins, in each case to create highly targeted agents. Using these technologies, we have built a pipeline of therapeutic product candidates that utilize several different mechanisms of action. We have exclusively licensed our lead product candidate, epratuzumab, to UCB for the treatment of all autoimmune disease indications worldwide. Epratuzumab's most advanced clinical testing is for the treatment of systemic lupus erythematosus (SLE) and in non-Hodgkin's lymphoma (NHL). At present, there is no cure for lupus and no new lupus drug has been approved in the U.S. in the last 40 years. We have retained the rights for epratuzumab in oncology indications, and are advancing trials in lymphoma and in childhood acute lymphoblastic leukemia in cooperation with National Cancer Institute Study Groups. In addition, the Company is conducting clinical trials with intravenous veltuzumab in patients with NHL and immune thrombocytopenic purpura, subcutaneous veltuzumab in NHL and chromic lymphocytic leukemia (CLL), 90Y-epratuzumab for the therapy of patients with lymphoma, 90Y-hPAM4 combined with gemcitabine for pancreatic cancer therapy, and milatuzumab (anti-CD74 humanized antibody) as a therapy for patients with multiple myeloma, NHL, and CLL. We also have a majority ownership in IBC Pharmaceuticals, Inc., which is developing a novel Dock-and-Lock (DNL) methodology for making fusion proteins and multifunctional antibodies, and a new method of delivering imaging and therapeutic agents selectively to disease, especially different solid cancers (colorectal, lung, pancreas, etc.), by proprietary, antibody-based, pretargeting methods. The Company is working to advance this new technology into clinical testing. We believe that our portfolio of intellectual property, which includes approximately 116 patents issued in the United States and more than 290 other patents issued worldwide, protects our product candidates and technologies. For additional information on us, please visit our website at http://www.immunomedics.com. The information on our website does not, however, form a part of this press release.

This release, in addition to historical information, may contain forward-looking statements made pursuant to the Private Securities Litigation Reform Act of 1995. Such statements, including statements regarding clinical trials, patent protection, out-licensing arrangements (including the timing and amount of contingent payments), forecasts of future operating results, and capital raising activities, involve significant risks and uncertainties and actual results could differ materially from those expressed or implied herein. Factors that could cause such differences include, but are not limited to, risks associated with new product development (including clinical trials outcome and regulatory requirements/actions), our dependence on our licensing partner for the further development of epratuzumab for autoimmune indications, competitive risks to marketed products and availability of required financing and other sources of funds on acceptable terms, if at all, as well as the risks discussed in the Company's filings with the Securities and Exchange Commission. The Company is not under any obligation, and the Company expressly disclaims any obligation, to update or alter any forward-looking statements, whether as a result of new information, future events or otherwise.

Immunomedics, Inc.
Dr. Chau Cheng, Associate Director, Investor Relations & 
 Business Analysis
(973) 605-8200, extension 123
ccheng@immunomedics.com