Immunomedics Presents Epratuzumab's Mechanism of Action in Systemic Lupus Erythematosus

Oral Presentation at EULAR 2013 Congress

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| Source: Immunomedics, Inc.

MADRID, Spain, June 13, 2013 (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 reported that epratuzumab, the Company's humanized anti-CD22 antibody, mediates the reduction of select proteins on the surface of B cells via a process known as trogocytosis, and that such reduction could modulate B-cell activities.Results from this study were presented by Edmund A. Rossi, Ph.D., Executive Director, Recombinant Technology.

Epratuzumab is currently in two UCB-conducted Phase III pivotal trials for the treatment of patients with systemic lupus erythematosus (SLE). UCB holds the worldwide development rights for epratuzumab in autoimmune diseases, while the Company retains all rights in oncology. In earlier clinical studies in SLE and in non-Hodgkin lymphoma (NHL), epratuzumab has been shown to deplete about 30-40% of circulating B cells in patients. However, the mechanism of action of epratuzumab, especially its involvement in regulating B-cell antigen receptor (BCR) signaling, has yet to be fully elucidated.

In this preclinical study, treatment of peripheral blood mononuclear cells (PBMCs) with epratuzumab significantly reduced the levels of select B-cell surface proteins, including CD22, CD19, CD21 and CD79b. Corroboratively, SLE patients on epratuzumab therapy also showed significantly lower levels of CD22, CD19 and CD21, compared to treatment-naïve patients. Although internalization of CD22 upon epratuzumab binding is known and expected, reduction of the other BCR proteins presents a new finding. The reduction of CD19 is of particular interest since elevated levels of this protein on the surface of B cells have been implicated in SLE.

Another key finding from this study is the formation of immunological synapses between B cells and effector cells, such as monocytes, natural killer cells and granulocytes, induced by epratuzumab. By binding to B cells and effector cells simultaneously, epratuzumab serves as a conduit for the transfer of the BCR-associated receptors, lowering their presence on B cells.

This process of trogocytosis occurred on B cells from healthy volunteers, NHL or SLE patients, over a broad concentration range between 10 ng/mL – 100 mg/mL of epratuzumab. This may explain the clinical observations that higher doses (720 mg/m2 weekly x 4) of epratuzumab were less effective than a mid-range dose (360 mg/m2 weekly x 4), because a serum concentration of epratuzumab greater than 150 µg/mL may reduce trogocytosis efficiency.

"We believe epratuzumab-mediated trogocytosis could modulate B-cell proteins involved in regulating BCR signaling and cell-cell communication, resulting in altered B-cell functions that ultimately mitigate symptoms of SLE and other autoimmune diseases, without major depletion of B cells," commented Cynthia L. Sullivan, President and Chief Executive Officer. "This study could potentially lead to the design of more effective therapy and the correct dosing for B-cell mediated autoimmune diseases and cancer," concluded Ms. Sullivan.

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™) method 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 223 active patents in the United States and more than 400 foreign patents, protects our product candidates and technologies. Our strength in intellectual property has resulted in the top-10 ranking in the 2012 IEEE Spectrum Patent Power Scorecards in the Biotechnology and Pharmaceuticals category. For additional information on us, please visit our website at 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 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.

For More Information:
Dr. Chau Cheng
Senior Director, Investor Relations & Grant Management
(973) 605-8200, extension 123