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Immunomedics Announces Sacituzumab Govitecan Is Synergistic With Chemotherapeutics That Target Cell Division in Triple-Negative Breast Cancer

BOSTON, Nov. 9, 2015 (GLOBE NEWSWIRE) -- Immunomedics, Inc. (Nasdaq:IMMU) today reported that new preclinical data for sacituzumab govitecan, the Company's lead antibody-drug conjugate (ADC) for solid cancer therapy, demonstrated synergy with olaparib, a poly(adenosine diphosphoribose) polymerase (PARP) inhibitor, as well as microtubule inhibitors, such as paclitaxel or eribulin mesylate, in various animal models of human triple-negative breast cancer (TNBC).

Sacituzumab govitecan, or IMMU-132, is a first-in-class ADC developed by the Company by conjugating the moderately-toxic drug, SN-38, site-specifically and at a high ratio of drug to antibody to a humanized antibody that targets the TROP-2 receptor expressed by many solid cancers. SN-38 is the active metabolite of irinotecan (Camptosar), which is used to treat certain solid cancers as a part of combination therapies, so its pharmacology and properties are well-known.

Clinically, sacituzumab govitecan has shown encouraging responses in metastatic TNBC patients, with only mild and manageable toxicity. The goal of this preclinical study was to determine whether the ADC's anti-tumor effects against TNBC could be enhanced in combination with other agents.

Sacituzumab govitecan combined with paclitaxel was evaluated in a mouse model of human TNBC. Tumor-bearing mice treated with the combination significantly inhibited tumor growth, resulting in a doubling of median survival when compared to all other treatments. Sacituzumab govitecan plus eribulin mesylate also produced significant survival benefit over other treatment groups. The median survivals of mice bearing a human TNBC cell line are summarized below:

Treatment Groups Paclitaxel Study Eribulin Study
Untreated 10 days 11 days
Paclitaxel (P) or Eribulin (E) alone 17.5 days 18 days
Non-targeting ADC alone 14 days 14 days
Sacituzumab Govitecan alone 17 days 14 days
Non-targeting ADC + P or E 17 days 19.5 days
Sacituzumab Govitecan + P or E 38 days 23 days

Synergy was also achieved when sacituzumab govitecan was combined with the PARP-inhibitor, olaparib, in another TNBC animal model. After more than 80.5 days, mice in the combination group had yet to reach median survival, which was more than 2- and 4-fold longer than the ADC or olaparib therapy alone, respectively.

"These new data provide the rationale for future clinical evaluation of sacituzumab govitecan therapy combined with these agents in patients with TNBC, and possibly other TROP-2-expressing cancers," commented Cynthia L. Sullivan, President and Chief Executive Officer. "More importantly, it suggests that DNA inhibitors, such as PARP and microtubule inhibitors now being used or studied in patients with BRCA1 mutations, such as breast and ovarian cancers, may benefit from combination therapy with sacituzumab govitecan, which is also a DNA inhibitor, causing DNA strand breaks," Ms. Sullivan added.

About Immunomedics

Immunomedics is a clinical-stage biopharmaceutical company developing monoclonal antibody-based products for the targeted treatment of cancer, autoimmune disorders and other serious diseases. Immunomedics' advanced proprietary technologies allow the Company to create humanized antibodies that can be used either alone in unlabeled or "naked" form, or conjugated with radioactive isotopes, chemotherapeutics, cytokines or toxins. Using these technologies, Immunomedics has built a pipeline of nine clinical-stage product candidates. Immunomedics' most advanced candidate is 90Y-clivatuzumab tetraxetan. The radiolabeled antibody is in a Phase 3 registration trial in patients with advanced pancreatic cancer. Immunomedics expects patient enrollment to be completed in calendar year 2016. Immunomedics' portfolio of investigational products also includes antibody-drug conjugates (ADCs) that are designed to deliver a specific payload of a chemotherapeutic directly to the tumor while reducing overall toxic effects that are usually found with conventional administration of these chemotherapeutic agents. Immunomedics' most advanced ADCs are sacituzumab govitecan (IMMU-132) and labetuzumab govitecan (IMMU-130), which are in Phase 2 trials for a number of solid tumors and metastatic colorectal cancer, respectively. Immunomedics has a research collaboration with Bayer to study epratuzumab as a thorium-227-labeled antibody. Immunomedics has other ongoing collaborations in oncology with independent cancer study groups. The IntreALL Inter-European study group is conducting a large, randomized Phase 3 trial combining epratuzumab with chemotherapy in children with relapsed acute lymphoblastic leukemia at clinical sites in Australia, Europe, and Israel. Immunomedics also has a number of other product candidates that target solid tumors and hematologic malignancies, as well as other diseases, in various stages of clinical and preclinical development. These include bispecific antibodies targeting cancers and infectious diseases as T-cell redirecting immunotherapies, as well as bispecific antibodies for next-generation cancer and autoimmune disease therapies, created using its patented DOCK-AND-LOCK® protein conjugation technology. The Company believes that its portfolio of intellectual property, which includes approximately 273 active patents in the United States and more than 400 foreign patents, protects its product candidates and technologies. For additional information on the Company, please visit its website at www.immunomedics.com. The information on its 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 (including the funding therefor, outcomes, timing or associated costs), 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, new product development (including clinical trials outcome and regulatory requirements/actions), the Company's dependence on business collaborations in order to further develop our products and finance our operations, the risk that we or any of our collaborators may be unable to secure regulatory approval of and market our drug candidates, risks associated with the outcome of pending litigation and 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: For More Information: Dr. Chau Cheng Senior Director, Investor Relations & Corporate Secretary (973) 605-8200, extension 123 ccheng@immunomedics.comSource:Immunomedics, Inc.