Immunomedics Reports First Results of Labetuzumab-SN-38 in Colorectal Cancer

WASHINGTON, April 9, 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 announced that its proprietary antibody-drug conjugate (ADC), labetuzumab-SN-38, appears to be safe and reasonably well tolerated within a clinically effective dosage range in patients with advanced colorectal cancer. Results from this Phase I study were presented by Dr. Neil H. Segal from the Memorial Sloan Kettering Cancer Center, New York, NY.

Labetuzumab-SN-38 is one of three agents from the Company's robust ADC program that are in clinical development. Labetuzumab is a slowly-internalizing antibody that recognizes the carcinoembryonic antigen (CEA; CEACAM5 or CD66e), which is expressed in many solid cancers, including more than 80% of colorectal cancer. In prior clinical trials, the antibody was shown to be safe when administered unconjugated or bound to the radioisotope, iodine-131, for radioimmunotherapy.

SN-38 is the active metabolite of irinotecan, which is a standard therapy for patients with metastatic colorectal cancer, but has major gastrointestinal and hematologic toxicity. By targeting SN-38 directly to CEA-expressing tumors, delivery of SN-38 may be increased while mitigating systemic toxicity. Preclinical studies have shown that the antibody-drug linkage was susceptible to cleavage in serum, with 50% of SN-38 released in ~1.0 day, leading to a locally enhanced concentration within the tumor site. In animal models of human colorectal cancer, the ADC exhibited high anti-tumor activity.

The goal of this single-arm, dose-escalation study was to determine the maximum-tolerated dose of labetuzumab-SN-38 in patients with metastatic colorectal cancer. Patients who had previously been treated with at least one prior irinotecan-containing regimen were enrolled to receive 2 doses of the ADC separated by 14 days. In the absence of unacceptable toxicity or disease progression, treatment continues for at least 24 weeks for a total of 12 cycles. Treatment may continue past 24 weeks if the patient reports a partial response or stable disease, with no unacceptable toxicity.

At the time of reporting, 11 patients with a median of 5 prior therapies have been treated at the 2, 4, 8, and 16 mg/kg dose levels. The average number of doses given was 3.9, with 6 of 11 patients receiving 3 or more doses. Five patients received 2 or more doses of 16 mg/kg, of which 1 has currently received 18 doses and has a continuing partial response after 8 doses.

One dose-limiting toxicity was observed at 16 mg/kg. Otherwise, the ADC was well tolerated. No human anti-humanized antibodies have been detected to date. Analysis of serum samples showed the intact conjugate clears more quickly than the antibody, consistent with SN-38 being gradually released from the ADC.

"These initial results are very encouraging," remarked Cynthia L. Sullivan, President and Chief Executive Officer of Immunomedics. "What differentiates our ADCs from other companies' products is the high ratio of drug to antibody, which, in labetuzumab-SN-38, is 6. While dose-escalation is continuing with this study, we are opening a new study with the same ADC in the same disease setting, but with a more intensive and a higher dosing schedule," added 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 220 active patents 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 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.

CONTACT: For More Information: Dr. Chau Cheng Senior Director, Investor Relations & Grant Management (973) 605-8200, extension 123 ccheng@immunomedics.comSource:Immunomedics, Inc.