(IMMU) Epratuzumab Featured in Official Journal of The American Society of Hematology

MORRIS PLAINS, N.J., Oct. 25, 2013  — 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 that an article published yesterday in Blood described a mechanism by which epratuzumab affects B cells. Epratuzumab is a humanized anti-CD22 antibody currently in Phase III trials conducted by the Company’s corporate partner, UCB (Euronext Brussels:UCB), as a therapeutic for patients with systemic lupus erythematosus (lupus).

The article was authored by several scientists of the Company, as well as a clinical collaborator, Dr. Daniel J. Wallace of Cedars-Sinai Medical Center of UCLA in Los Angeles, CA. The article was featured on the cover of this issue of Blood with a fluorescence microscopy image, showing how epratuzumab can translocate certain surface proteins on B cells to other blood cells, a process called trogocytosis.

Accompanying the article was an invited commentary by Dr. Ronald P. Taylor of the University of Virginia School of Medicine, who is a pioneer on studies of trogocytosis involving anti-B-cell antibodies, such as rituximab.

In the article by Rossi and colleagues of Immunomedics, it was demonstrated that epratuzumab can induce trogocytosis of CD22, CD21, CD19, and several other B-cell surface molecules from lymphocytes to other blood cells, such as monocytes, natural killer cells, and granulocytes. Epratuzumab is distinct from other B-cell antibodies, such as rituximab, because it does not drastically deplete B cells, but instead compromises B-cell autoimmune activity.

The Immunomedics scientists postulated that removal of CD22, CD19, CD21 and other proteins from the surface of B cells reduces the autoimmune activity of these cells. In fact, B cells obtained from lupus patients who were treated with epratuzumab showed reduced CD22, CD19 and CD21. The authors suggest that this modulation of B cells via trogocytosis could be the major mechanism of epratuzumab in patients with lupus.

Cynthia L. Sullivan, President and CEO of Immunomedics, commented: “We are gratified that we have advanced our knowledge on how epratuzumab, which is completing Phase III trials in patients with moderate and severe lupus, may affect antigen-presenting B cells in this autoimmune disease without having a major depletion of this population of blood cells needed to protect individuals from infections. Having an effect of down-regulating CD19, CD21, and other surface molecules on B cells, is an unexpected finding, and is consistent with the view by some that CD19 is a key molecule that is increased in autoimmune disease.”

About Systemic Lupus Erythematosus (SLE)

SLE or lupus, is a complex, systemic, autoimmune disease that affects many different organ systems, including the skin, joints, lungs, kidneys and blood. Disease activity and rate of progression of organ system damage is highly variable. SLE affects from 20 to 70 people per 100,000 population, and is rare in childhood. It is 10 times more common in women than men.

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. Our lead product candidate, epratuzumab, is currently in two Phase III clinical trials in lupus. In oncology, we are planning to launch a Phase III pivotal trial for clivatuzumab labeled with a radioisotope in advanced pancreatic cancer patients. Other solid tumor therapeutics in Phase II clinical development include 2 antibody-drug conjugates, labetuzumab-SN-38 (IMMU-130) and hRS7-SN-38 (IMMU-132). 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. DNL™ is being used particularly to make bispecific antibodies targeting cancers and infectious diseases as a T-cell redirecting immunotherapy, as well as bispecific antibodies for next-generation cancer and autoimmune disease therapies. We believe that our portfolio of intellectual property, which includes approximately 231 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 UCB for the further development of epratuzumab 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.

CONTACT: Dr. Chau Cheng
         Senior Director, Investor Relations & Grant Management
         (973) 605-8200, extension 123
         ccheng@immunomedics.com