- First HER2 Tyrosine Kinase Inhibitor in Combination to Show Improved Progression-Free Survival and Overall Survival in Patients with Metastatic HER2-Positive Breast Cancer With or Without Brain Metastases -

- NDA and MAA On Track for Submission by First Quarter of 2020 -

BOTHELL, Wash.--(BUSINESS WIRE)-- Seattle Genetics, Inc. (Nasdaq:SGEN) today announced positive pivotal data from the HER2CLIMB trial evaluating tucatinib in patients with HER2-positive metastatic breast cancer (MBC) were presented at the 2019 San Antonio Breast Cancer Symposium (SABCS) and simultaneously published in the New England Journal of Medicine (NEJM). The HER2CLIMB trial compared tucatinib in combination with trastuzumab and capecitabine to trastuzumab and capecitabine alone in patients with unresectable locally advanced or metastatic HER2-positive breast cancer. Patients had previously received trastuzumab, pertuzumab and ado-trastuzumab emtansine (T-DM1). Patients had received a median of four prior lines of therapy overall and three lines in the metastatic setting. Forty-seven percent of the patients enrolled in the trial had brain metastases at the time of enrollment. HER2CLIMB is the first randomized pivotal trial completed to enroll patients with metastatic HER2-positive breast cancer who have untreated or previously treated and progressing brain metastases. Tucatinib is an oral, small molecule tyrosine kinase inhibitor (TKI) that is highly selective for HER2.

“Following progression on trastuzumab, pertuzumab and T-DM1 in the metastatic HER2-positive breast cancer setting, there is no single standard of care regimen and clinical trial participation is often strongly encouraged. There is a significant unmet medical need for these patients, particularly those who develop brain metastases,” said Rashmi Murthy, MD, MBE, Assistant Professor, Department of Breast Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center. “The addition of tucatinib to the commonly used combination of trastuzumab and capecitabine improved overall survival, reducing the risk of death by 34 percent compared to trastuzumab and capecitabine alone. The results from HER2CLIMB demonstrate tucatinib has the potential to become a new treatment option for patients who have been previously treated with multiple anti-HER2 agents, including patients with and without brain metastases.”

“Continued innovation to bring new therapies for the treatment of metastatic HER2-positive breast cancer is urgently needed, and we are encouraged by the impressive clinical activity demonstrated with the addition of tucatinib to trastuzumab and capecitabine in the HER2CLIMB trial,” said Roger Dansey, M.D., Chief Medical Officer at Seattle Genetics. “Tucatinib demonstrated a statistically significant and clinically meaningful benefit in overall survival, progression-free survival and objective response rate compared to the control arm. We plan to submit a New Drug Application (NDA) to the U.S. Food and Drug Administration and a Marketing Authorization Application (MAA) to the European Medicines Agency by the first quarter of 2020, with the goal of bringing a much-needed new medicine to patients.”

Data presented at SABCS and published in NEJM include the primary endpoint of progression-free survival (PFS) as assessed by blinded independent central review (BICR) in the first 480 patients enrolled in the trial. HER2CLIMB enrolled a total of 612 patients to support the analyses of key secondary endpoints, including overall survival (OS) as well as progression-free survival (PFS) in patients with brain metastases at baseline.

Pivotal HER2CLIMB Trial Results

Efficacy:

• The primary endpoint of PFS showed that the addition of tucatinib was superior to trastuzumab and capecitabine alone, with a 46 percent reduction in the risk of disease progression or death (hazard ratio (HR)=0.54 [95% Confidence Interval (CI): 0.42, 0.71]; p