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news.Immunomedics, announced that sacituzumab govitecan, the company's lead investigational antibody-drug conjugate (ADC), produces partial response (PR) in some patients with metastatic esophageal and colorectal cancers who had been heavily pretreated.
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Extended periods of stable disease were also noted in some patients with pancreatic and gastric cancers, with time-to-progression (TTP) exceeding that of last prior therapy in many cases. Response and TTP were evaluated by computed tomography (CT) based on RECIST criteria.
Patented and developed by the Company, sacituzumab govitecan was created 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, particularly metastatic colorectal cancers, as a part of combination therapies, so its pharmacology and properties are well-known.
Dr. Alexander N. Starodub of Indiana University Health Center for Cancer Care, Goshen, IN, presented the Phase 1/2 study at the 2015 Gastrointestinal Cancers Symposium co-sponsored by the American Gastroenterological Association (AGA), the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), and the Society of Surgical Oncology (SSO) in San Francisco, CA.
A total of 63 patients with various types of gastrointestinal cancers had been enrolled into this multicenter study. At the time of analysis, 26 patients with colorectal cancer, 13 with esophageal cancer, 3 with gastric cancer and 14 with pancreatic cancer were evaluated by CT for response and TTP. Median numbers of prior treatments ranged from 2 for pancreatic cancer to 4 in colorectal cancer.
Despite the late-stage setting, 1 patient in each of the colorectal and esophageal cancer groups had a partial response after receiving more than 2 doses of the ADC. For all 4 cancer types, the disease stabilization rate (partial response + stable disease) exceeded 50%.
Commenting on these results, Cynthia L. Sullivan, President and Chief Executive Officer, stated, "This novel ADC is encouraging as a monotherapy, as demonstrated in this trial. We have also conducted additional preclinical testing that indicates it is suitable for combination therapy in these gastrointestinal cancers."
Repeated cycles of therapy with sacituzumab govitecan over many months were well tolerated by patients and did not produce the typical side effects of irinotecan treatment other than neutropenia. Transient neutropenia was the major toxicity (18% Grade 3 and 6% Grade 4), followed by febrile neutropenia 4%, and diarrhea 3% Grade 3.
In addition to Dr. Starodub of Indiana University Health Center for Cancer Care, the multicenter study also involved Drs. Allyson J. Ocean and Manish A. Shah, Weill Cornell Medical College, New York, NY; Dr. Wells A. Messersmith, University of Colorado Cancer Center, Aurora, CO; Dr. Vincent J. Picozzi, Virginia Mason Cancer Center, Seattle, WA; Dr. Michael J. Guarino, Helen F. Graham Cancer Center & Research Institute, Newark, DE; Dr. Sajeve S. Thomas, UF Health Cancer Center-Orlando Health, Orlando, FL; and Dr. Aditya Bardia, Massachusetts General Hospital Cancer Center, Termeer Center for Targeted Therapies, Boston, MA.