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 repeated therapy cycles of its proprietary antibody, clivatuzumab tetraxetan, labeled with yttrium-90 (Y-90) plus low-dose gemcitabine at 200 mg/m2, extended median overall survival (OS) to 11.8 months, more than double the 5.4 months OS in patients treated with a single cycle. Increased Y-90 doses also improved responses; patients receiving a dose of 12 mCi/m2 or higher once a week for 3 weeks reporting a median OS of 8.0 months versus 6.0 months at doses of 9 mCi/m2 or less, once a week for 3 weeks.
These encouraging results were updated at the 2011 Gastrointestinal Cancers Symposium, which is co‐sponsored by the American Gastroenterological Association Institute, the American Society of Clinical Oncology, the American Society for Radiation Oncology, and the Society of Surgical Oncology.
At the Symposium, results from 50 evaluable patients were reported. The overall disease control rate for all dose groups, including those that received gemcitabine at greater than 200 mg/m2, was 60%, with 7 patients (14%) reporting a partial response by RECIST criteria (i.e., responses showing decreases in tumor size of more than 30% by CT and the absence of new lesions) and 23 patients (46%) with disease stabilization. Metabolic imaging with PET and the biomarker, CA19-9, both provided supportive evidence of anti-tumor activity.
Commenting on these encouraging results, Dr. Allyson Ocean of the New York Presbyterian Hospital, Weill Medical College of Cornell University, New York, NY, stated, "This is the first time we are reporting survival benefits with this antibody, which are significant in pancreatic cancer. Shrinkage of primary tumors in patients with advanced, inoperable pancreatic cancer is extremely rare. Equally important are improvements in quality-of-life, particularly in the reduction of pain, we have witnessed in our patients."
To date, more than 70 patients with locally advanced or metastatic pancreatic cancer have been treated with the regimen involving Y-90-labeled clivatuzumab tetraxetan administered once a week for 3 weeks, in combination with gemcitabine. Treatments were well tolerated, including 16 patients retreated with 1-3 additional cycles, with few non-hematologic side effects. In spite of higher cumulative Y-90 doses, hematologic suppression was transient and occurred without major infections or bleeding events.
The open-label study is continuing with new patients enrolled to receive Y-90-labeled clivatuzumab tetraxetan at 12 mCi/m2 once a week for 3 weeks, and gemcitabine at higher doses, including the standard-of-care dose of 1000 mg/m2.
"We are pleased that clivatuzumab tetraxetan continues to produce encouraging results in this difficult-to-treat disease, and we look forward to evaluating this compound in randomized clinical trials," remarked Cynthia L. Sullivan, President and CEO of Immunomedics. "We plan to complete this dose-escalation study shortly and to seek regulatory advice on protocols designed to determine response rates and overall survival for the future development of this agent," added Ms. Sullivan.