Immunomedics Reports Development of a New Labeling Kit for Attaching Fluorine-18 to Peptides and Temperature-Sensitive Biomolecules, Including Antibodies

Results Presented at the 59th Annual Meeting of Society of Nuclear Medicine (SNM)

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| Source: Immunomedics, Inc.

MIAMI BEACH, Fla., June 11, 2012 (GLOBE NEWSWIRE) -- Immunomedics, Inc. (Nasdaq:IMMU), a biopharmaceutical company primarily focused on the development of monoclonal antibody-based products for the targeted treatment of cancer, autoimmune and other serious diseases, today announced the development of a lyophilized kit for the rapid and facile labeling of peptides with fluorine-18 (18F) with good yields and high specific activity.

The Company previously reported a novel method of radiolabeling peptides with 18F for use in positron emission tomography (PET) imaging of diseases. (Please refer to the Company's press release at www.immunomedics.com/pdfs/news/2009/PR05182009A.pdf for more information on the labeling method). The newly patented method, which has since been refined to a 30-minute process, involves the initial formation of an aluminum-18F complex (Al18F) and is applicable to essentially any peptide that is heat stable.

In order to further simplify the procedure and make the process more consistent and for broader use, the Company has formulated a lyophilized kit that could be validated and manufactured under Good Manufacturing Practice (GMP) conditions. The kit contains aluminum, a radioprotectant, a non-volatile buffer, a bulking agent and a peptide to be labeled with 18F.

A kit containing 20 nmol of the peptide IMP485 was labeled in a semi-automated machine that heats and performs all of the labeling operations, except for the addition of 18F. The radiolabeled peptide, Al18F-IMP485, was obtained in approximately 70% yield under non-optimized condition.

With a fully automated microfluidics machine, the reaction time was reduced to 1.5 minutes. More importantly, 1.2 nmol of IMP485 was 18F-labeled with a non-optimized 44% yield and a specific activity of 37-74 GBq/µmol (1,000-2,000 Ci/mmol) in amounts that are in the range of a single patient dose. To date, the maximum specific activity achieved was 222 GBq/µmol or 6,015 Ci/mmol.

For the radiofluorination of biomolecules that are heat-sensitive, such as antibodies and antibody fragments, which is the subject of a poster presentation given earlier at this year's SNM annual meeting, the use of Al18F-chelated prosthetic groups was necessary. These prosthetic groups are based on the ligand called NODA, which can form a physiologically stable complex with aluminum and has an open coordination site for 18F.

In this modified method, the 18F-labeled prosthetic groups are first synthesized by heating the NODA-based ligands with a mixture of aluminum and 18F for 10 – 15 minutes, before they are securely linked to the heat-sensitive biomolecules. Each prosthetic group has a unique functionality that enables them to form a covalent linkage with the biomolecules in a site specific manner at room temperature.

The 18F-labeled prosthetic groups were obtained in high yields (70-82%) in an aqueous medium. Furthermore, the 18F-labeled biomolecules did not undergo defluorination up to 4 hours in human serum at 37°C, and retained their immunoreactivity.

"Based on our Al18F-chelation methodology, we believe these studies formed a platform for the generation of numerous 18F-labeled biomolecules in aqueous medium that are potentially useful for the PET imaging of diseases, especially various forms of antibodies," remarked Cynthia L. Sullivan, President and Chief Executive Officer.

These two studies were supported in part by Award Number R44RR028018 from the National Center for Research Resources and the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health.

About Immunomedics

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. 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, cytokines 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 also have a majority ownership in IBC Pharmaceuticals, Inc., which is developing a novel Dock-and-Lock (DNL) methodology with us 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. We believe that our portfolio of intellectual property, which includes approximately 199 patents issued in the United States and more than 400 foreign patents, protects our product candidates and technologies. For additional information on us, please visit our website at http://www.immunomedics.com/ http://www.immunomedics.com/ blocked::http://www.immunomedics.com/">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, out-licensing arrangements (including the timing and amount of contingent payments), forecasts of future operating results, potential collaborations, 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 any cash payment that the Company might receive in connection with a sublicense involving a third party and UCB, which is not within the Company's control, new product development (including clinical trials outcome and regulatory requirements/actions), our dependence on our licensing partners for the further development of epratuzumab for autoimmune indications and veltuzumab for non-cancer 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.

Dr. Chau Cheng
Director, Investor Relations & Grant Management
(973) 605-8200, extension 123