Precision medicine data on DS-8201

Daiichi Sankyo Company, Limited (hereafter, Daiichi Sankyo) announced smart chemotherapy DS-8201 demonstrated a favorable safety profile and promising antitumor activity in patients with HER2-expressing tumors, including pre-treated metastatic breast and gastric cancer. These data were highlighted as part of a Clinical Science Symposium at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting.

Preliminary results from the dose expansion part of the phase 1 study of DS-8201 in a subgroup analysis of HER2-expressing metastatic breast cancer patients pre-treated with ado-trastuzumab emtansine (T-DM1) and pertuzumab demonstrated a 46.7 percent overall response rate (14 of 30 patients) and a 100 percent disease control rate (30 of 30 patients) to date. An overall response rate of 45.7 percent (16 of 35 patients) and disease control rate of 100 percent (35 of 35 patients) was observed in patients pre-treated with only T-DM1.

Antibody drug conjugates (ADCs) are a type of targeted cancer medicine that deliver cytotoxic chemotherapy ("payload") directly to cancer cells via a linker attached to a monoclonal antibody that binds to a specific target expressed on cancer cells. Using Daiichi Sankyo’s proprietary ADC technology, DS-8201 is a smart chemotherapy comprised of a humanized HER2 antibody attached to a novel topoisomerase I inhibitor (DXd) payload by a tetrapeptide linker designed to deliver enhanced cancer cell destruction upon release inside the cell and reduce systemic exposure to the cytotoxic payload (or chemotherapy).

"The significant tumor shrinkage and sustained tumor control that was demonstrated by DS-8201 is impressive and further confirms the initial antitumor activity shown in the dose escalation part of this study," said Toshihiko Doi, MD, PhD, Department of Experimental Therapeutics, National Cancer Center Hospital East, and study investigator. "These data suggest that DS-8201 may be a promising potential treatment for patients with HER2-expressing metastatic breast cancer whose tumors are no longer controlled with available treatment options like T-DM1 and pertuzumab."

Thirty-nine of 50 patients with HER2-expressing metastatic breast cancer are continuing to receive treatment. To date, median progression free survival has reached 45.4 weeks (95 percent CI: 32.1, NA). Eleven patients have discontinued treatment due to adverse events (3 patients), progressive disease (6 patients) and other reasons (2 patients).

"These results demonstrate that the smart delivery of chemotherapy by DS-8201 to cancer cells may be effective and safe in treating tumors that express HER2," said Antoine Yver, MD, MSc, Executive Vice President and Global Head, Oncology Research and Development, Daiichi Sankyo. "Based on these results, we are accelerating the development of DS-8201 and our ADC technology seeking to bring a unique precision medicine to patients and physicians who have exhausted current treatment options."