Seattle Genetics Inc. submitted a new drug application with the U.S. Food and Drug Administration seeking approval of its breast cancer medicine tucatinib.

The Bothell, Wash.-based biotechnology company is developing tucatinib to treat patients with HER2-positive breast cancer whose disease has spread to nearby tissue or lymph nodes and cannot be surgically removed or has spread to other parts of the body, including the brain, and those who have received at least three prior HER2-targeted agents either individually or in combination as treatment.

The application is based on results from a phase 2 trial called HER2Climb which showed that tucatinib combined with trastuzumab, sold by Roche Holding AG as Herceptin and capecitabine, a drug also marketed by Roche as Xeloda, was better than trastuzumab and capecitabine alone in treating patients with this type of breast cancer.

Tucatinib was recently given the U.S. regulator's breakthrough-therapy designation in combination with trastuzumab and capecitabine for the same indication.