SAN FRANCISCO, Jan. 24, 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 announced that combining antibody-directed drug and radionuclide therapeutics for pancreatic cancer improved efficacy in preclinical studies with minimal toxicity. Results from these investigations were presented at the 2011 Gastrointestinal Cancers Symposium. Two of the Company's proprietary humanized antibodies were involved in this research. Clivatuzumab, which selectively targets pancreatic cancer, has shown in preclinical and early clinical studies promising therapeutic activity when labeled with yttrium-90 (Y-90) and in combination with gemcitabine. hRS7 has been shown to internalize into cancer cells when bound to its receptor, EGP-1, or TROP-2, making it an attractive antibody for delivery of cytotoxic drugs. Since TROP-2 has higher expression in lung, breast, prostate, ovarian, colorectal, pancreatic and cervical cancers than in normal tissues, the Company has previously conjugated SN-38, the active metabolite of irinotecan approved as a chemotherapeutic agent for metastatic colorectal cancer, to hRS7 for targeted treatment of cancer. In preclinical studies, hRS7-SN-38 has demonstrated potent therapeutic effects against lung cancer. (Please refer to the Company's press release at http://www.immunomedics.com/news_pdf/2008_PDF/PR03202008.pdf for more information). Using nude mice bearing human pancreatic cancer cells as a model, the goal of the current studies was to evaluate the possibility that hRS7-SN-38, at effective, yet non-toxic doses, could augment therapeutic responses with Y-90-labeled clivatuzumab tetraxetan. Clivatuzumab-SN-38 conjugate was also included in these evaluations. Irinotecan, given at a dose that contained the same amount of SN-38 as the antibody-drug conjugates (ADC), was not effective in controlling tumor growth, while each ADC alone was able to inhibit tumor growth significantly compared to untreated animals. When ADC was combined with the radiolabeled antibody, time to progression (TTP) improved considerably and more animals were tumor-free. Importantly, an effective ADC dose can be combined at the maximum tolerated dose (MTD) of Y-90 clivatuzumab tetraxetan with minimal additional toxicity.