NEW YORK – Seagen on Monday said the UK's Medicines and Healthcare products Regulatory Agency (MHRA) has authorized its anti-HER2 agent tucatinib (Tukysa) with trastuzumab (Genentech's Herceptin) and chemotherapy for HER2-positive, locally advanced, or metastatic breast cancer patients who have previously received at least two prior anti-HER2 treatment regimens.