On September 13, 2016 Siamab Therapeutics, Inc., a biotechnology company developing novel cancer immunotherapies, reported new pre-clinical data that showed its novel ST1 antibody drug conjugates (ADCs) target chemoresistant ovarian cancer cells and demonstrate strong efficacy in ovarian cancer models (Press release, Siamab Therapeutics, SEP 13, 2016, View Source [SID:SID1234515130]). These data were presented at the American Association for Cancer Research (AACR) (Free AACR Whitepaper)’s 11th Biennial Ovarian Cancer Research Symposium 2016 in Seattle, Wash., on Monday, Sept. 12, 2016.
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"The preclinical results are exciting and show the potential of our antibody approach to target chemoresistant tumors in ovarian cancer"
Siamab’s ST1 ADCs target the cancer associated antigen, sialyl-Tn (STn) with high specificity and affinity. STn is present on multiple solid tumors including ovarian, pancreatic, prostate and colon, while showing little normal tissue expression, and has been implicated in immune suppression, metastasis, and a cancer stem cell phenotype.
"The preclinical results are exciting and show the potential of our antibody approach to target chemoresistant tumors in ovarian cancer," said Jeff Behrens, president and chief executive officer of Siamab Therapeutics. "We have developed multiple anti-glycan antibodies and ADCs with unprecedented cancer specificity and efficacy in animal models. These findings hold promise for developing new cancer therapeutics for ovarian cancer patients with disease recurrence who have limited treatment options."
The preclinical data were presented in a poster titled "Targeting a chemoresistant ovarian cancer cell population via the carbohydrate antigen sialyl Tn." The findings showed that Siamab’s ST1 ADCs significantly reduce tumor volume in a sustained fashion in ovarian cancer models. In addition, Siamab’s ST1 target, STn, demarks a population of cells that display a cancer stem cell phenotype as demonstrated by colony- and sphere-forming assays. The findings also showed that following platinum- and taxane-based cytotoxic chemotherapy, STn+ cancer cells are significantly enriched, further supporting their cancer stem cell and chemoresistant phenotype.
Siamab collaborated with Bo Rueda, Ph.D., director of the Vincent Center for Reproductive Biology, in the Department of Obstetrics and Gynecology at Massachusetts General Hospital on this research, funded by a National Cancer Institute SBIR Phase I contract. The collaboration explored the potential of Siamab’s anti-glycan antibodies to target populations of chemoresistant cancer cells. This research also looked at the relationship between tumor associated carbohydrate antigens (TACAs) and chemoresistant cancer cells that demonstrate a cancer stem cell (CSC) phenotype.
"We know chemoresistant cancer cells play a central role in disease recurrence and are particularly challenging to target," said Dr. Rueda. "Siamab’s ADCs targeted STn positive cells, demarking a chemoresistant population, and were effective in shrinking ovarian tumors in animal models. I look forward to continuing to work closely with Siamab as they move this program toward clinical development."