Daiichi Sankyo Presents Updated Phase 1 Data for U3-1402 in Patients with HER3-Expressing Metastatic Breast Cancer at 2018 San Antonio Breast Cancer Symposium (SABCS)

- Updated efficacy and safety results presented from ongoing phase 1/2 study with U3-1402, an investigational and potential first-in-class HER3-targeting antibody drug conjugate (ADC), in patients with heavily pretreated HER3-positive metastatic breast cancer

- Preliminary efficacy data demonstrated a 42.9 percent confirmed overall response rate and a 90.5 percent disease control rate at a median follow-up time of 10.5 months

- No therapies are specifically approved for HER3-expressing breast cancer, and findings with U3-1402 continue to support the portability of Daiichi Sankyo's proprietary DXd and linker ADC technology

TOKYO and MUNICH and BASKING RIDGE, N.J., Dec. 5, 2018 /PRNewswire/ -- Daiichi Sankyo Company, Limited (hereafter, Daiichi Sankyo) announced that updated efficacy and safety results from the ongoing phase 1/2 study of U3-1402, an investigational and potential first-in-class HER3-targeting antibody drug conjugate (ADC), in 42 heavily pretreated patients with HER3-positive metastatic breast cancer were presented during a Spotlight Session at the 2018 San Antonio Breast Cancer Symposium (SABCS).

Updated efficacy data for 42 evaluable patients who received U3-1402 in dose levels between 1.6 mg/kg to 8.0 mg/kg in the dose escalation and dose finding parts of the study showed a confirmed overall response rate of 42.9 percent (18/42 patients) and a disease control rate of 90.5 percent (38/42 patients) at a median follow-up time of 10.5 months. A median duration of response was not reached (range: 2.8, 13.8+). The median progression-free survival was 8.3 months (range: 1.2, 16.8+). Efficacy was observed in all molecular subtypes. A total of 21 patients remain on treatment at the time of data cut-off on November 6, 2018.

"These results offer preliminary evidence of U3-1402 activity in HER3-positive metastatic breast cancer and further study is warranted," said Norikazu Masuda, MD, PhD, National Hospital Organization, Osaka National Hospital, Osaka, Japan, and an investigator for the trial. "The initial efficacy and safety data suggest that a HER3-targeting agent such as U3-1402 could provide a new treatment approach for patients with HER3-expressing metastatic breast cancer, who are in need of additional options to manage their disease."