Siamab Therapeutics Presented New Data for its Anti-STn Antibody Therapeutics Showing Myeloid-Derived Suppressor Cells as a Promising Cancer Immunotherapy Target at Cambridge Healthtech Institute’s Targeting Tumor Myeloid Cells Conference

Preclinical Data Findings Show STn Expression on Myeloid Derived Suppressor Cells Offers a Potential Targeting Mechanism for Treatment of Solid Tumors

NEWTON, MA, USA I September 29, 2017 I Siamab Therapeutics, Inc., a biopharmaceutical company developing novel cancer immunotherapies, today announced it presented new preclinical data for its novel anti-Sialyl-Tn (STn) antibodies and antibody drug conjugates (ADCs) targeting myeloid-derived suppressor cells (MDSCs) at Cambridge Healthtech Institute’s Inaugural Targeting Tumor Myeloid Cells Conference, held September 27-28, 2017 in Boston. Siamab’s data show that STn, a tumor-associated carbohydrate antigen (TACA), is expressed not only on tumor cells, but also on tumor infiltrating MDSCs, providing a potential new therapeutic target. MDSCs are major regulators of immune response in cancer and other pathological conditions, and play a critical role in the tumor microenvironment by suppressing T cell immunity.

During the oral and poster presentations, Siamab reported data from primary human cancer samples as well as from two in vivo murine studies. In the studies, Siamab scientists used monoclonal antibodies (mAbs) to quantify the expression of STn across patient tumors, and for the first time demonstrated the expression of STn on subsets of tumor infiltrating immune cells, specifically MDSCs. The findings showed that STn provides a uniquely glycan-specific and potent targeting mechanism for the treatment of solid tumors using Siamab’s anti-STn antibody drug conjugates. Additionally, the findings showed a correlation between MDSC STn expression and tumor STn expression using murine xenograft models of tumors with controlled STn expression.

“These preclinical findings are important as they reveal that STn expression on MDSCs offers the possibility to go beyond tumor targeting with an anti-STn antibody therapeutic to directly target and deplete immune suppressive MDSCs and re-engage the immune system,” said Jeff Behrens, president and chief executive officer of Siamab. “We are encouraged by these results which further our understanding of MDSCs and suggest the potential for a functional role of STn, highlighting the possibility to directly impact MDSC function with immuno-therapeutic applications. We look forward to further evaluating our anti-STn antibody therapeutics against STn expressing solid tumors and MDSCs.”

Siamab is developing mAb therapeutics that target TACAs, a novel class of cancer-specific antigens that are implicated in immune suppression, chemoresistance, and a cancer stem-cell phenotype. STn is an exciting TACA target due to its high cancer specificity and strong correlation with increased tumor malignancy. STn is rarely expressed in normal adult human tissues; however, it is highly expressed in numerous human adenocarcinomas, including ovarian, pancreatic, prostate, colon, gastric, and breast cancers. STn expression has been linked to innate immune suppression, a chemoresistant stem-cell phenotype, invasion/metastasis, and poor prognosis.

The poster presentation, titled Novel targeting of tumor infiltrating myeloid derived suppressor cells (MDSCs) through expression of the tumor-specific glycan antigen Sialyl Tn (STn), can be found on the Siamab Therapeutics website.

About Siamab Therapeutics, Inc.

Siamab Therapeutics, Inc. is a biopharmaceutical company developing novel cancer immunotherapies targeting cancer-specific carbohydrate antigens seen in multiple solid tumors. Siamab has developed a platform that enables the rapid discovery and development of therapeutic antibodies that bind with unprecedented specificity and affinity to this novel class of carbohydrate antigens present on cancer cells called tumor associated carbohydrate antigens (TACAs). TACAs are an exciting cancer target class due to their cancer specificity, association with a chemoresistant phenotype, and ability to suppress immune function in the region of solid tumors. The company’s lead program, ST1, targets Sialyl-Tn (STn), a tumor specific antigen seen in multiple solid tumors including ovarian, pancreatic, prostate and colon cancers. ST1 is in late-stage preclinical studies for the treatment of solid tumors. Visit to learn more about the company.

SOURCE: Siamab Therapeutics

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