updated 6/6/2011 12:46:43 PM ET 2011-06-06T16:46:43

  • Pretargeted Radiation Therapy With Bispecific Antibody Selected by Society of Nuclear Medicine (SNM) as Newsworthy for 2011 Annual Meeting Press Conference
  • Pretargeted Radioimmunotherapy in Medullary Thyroid Cancer Patients Also Reported

SAN ANTONIO, June 6, 2011 (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 pretargeted radiation therapy with TF2, a humanized bispecific antibody owned by the Company, appears to be safe and tolerable in patients with advanced colorectal cancer. Results from the Phase I study were released by SNM at its 58th Annual Meeting Press Conference.

In this study, a new approach to antibody-directed radiation therapy, or radioimmunotherapy (RAIT), called pretargeting, was used. Developed by IBC Pharmaceuticals, Inc., the Company's majority-owned subsidiary, pretargeted RAIT (PT-RAIT) requires the use of a different type of antibody called a bispecific antibody. Unlike traditional antibodies having both arms binding only to one receptor, bispecific antibodies have been engineered so that each arm recognizes two different targets, one for the tumor and the other for the agent that carries radioactive materials.   TF2, created by the Company's patented Dock-and-Lock (DNL) protein engineering platform, recognizes carcinoembryonic antigen (CEA or CEACAM5) expressed by many human cancers, as well as a small radioisotope-carrying peptide called HSG (histamine-succinyl-glycine).   

A key feature of PT-RAIT is that radioactive materials are introduced in a second step through the injection of a small peptide that the bound antibody also recognizes. The agent either attaches quickly to the antibody localized at the tumors or, due to its small size, is rapidly excreted in the urine, thereby minimizing the body's exposure to radiation. Another advantage of PT-RAIT is in the higher radiation dose level delivered selectively to the tumors.

The aims of the Phase I study are to determine and optimize the pharmacokinetics and tumor targeting of TF2 and the radiolabeled peptide, as well as to evaluate the therapeutic potential and the safety and toxicity of this PT-RAIT in patients with advanced colorectal cancer. Results from 4 cohorts of patients who received 75 or 150 mg of TF2 followed 1 or 5 days later with 25 or 100 µg of the radioactive peptide were presented at the annual meeting by investigators from the University Medical Center in Nijmegen, The Netherlands.

Pretargeting with TF2 and the specific labeled peptide target tumor lesions in colorectal cancer patients rapidly and produced high tumor-to-background ratios. TF2 is cleared quickly from the blood. As a result, a short interval between the infusion of TF2 and the injection of peptide is preferred. Moreover, high doses of radiolabeled peptide can be administered safely with only bone marrow toxicity as dose-limiting.

"This is 1 of 2 investigator-sponsored studies in Europe involving TF2 for pretargeted imaging and radioimmunotherapy of colorectal and lung cancers," commented Cynthia L. Sullivan, President and CEO.  "We will initiate our own clinical trials of TF2 in patients with metastatic colorectal cancer, where patient enrollment is anticipated to begin this summer at several U.S. investigational sites," Ms. Sullivan added.

In a separate oral presentation, results from a Phase II clinical trial of PT-RAIT in progressive medullary thyroid cancer (MTC) were reported. The disease represents 5 to 10% of thyroid cancers with a relatively slow tumor growth, but early spread to the lymphatic system. Response rate to chemotherapy is less than 30%. 

MTC expresses high amount of CEA and is, therefore, a good candidate for RAIT. Two previous Phase I/II studies with PT-RAIT demonstrated efficacy in MTC patients. The current multicenter Phase II trial aims to evaluate PT-RAIT in progressing MTC patients with metastatic disease using a combined response that includes CT-RECIST, PET and biomarker concentration to assess efficacy.

Results from 42 patients were presented at the medical conference by investigators from the University Medical Center in Nantes, France. Overall, 20 patients (47.6%) responded to the pretargeted therapy. Significantly, the median survival of patients who responded was 67 months compared to 25 months in patients who failed the treatment. These results suggest that anti-CEA PT-RAIT has the potential to treat MTC patients with progressing, metastatic disease.

About Pretargeted Radioimmunotherapy

Pretargeted radioimmunotherapy (PT-RAIT) uses a 'two-step' approach in the delivery of therapeutic isotope. A humanized bispecific monoclonal antibody (bsMAb), with one arm that recognizes a tumor-associated antigen and another arm that recognizes a peptide that carries a therapy agent, is given as a first injection. When non-tumor-bound bsMAb has substantially cleared non-target tissues and bsMAb has reached a maximum level in the tumor, the bsMAb-recognizable therapy agent is given. The latter agent either targets the bsMAb localized at the tumor, or it is rapidly cleared through urine via the kidneys. PT-RAIT is an attractive potential alternative to traditional RAIT, because the delivery of therapeutic isotope is rapid and is separated from the long antibody delivery process, thereby reducing the harmful effects of radiation to the body, especially the bone marrow. 

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 178 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 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, 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 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.

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

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