In 2020, the FDA approved the use of tucatinib in combination with capecitabine and trastuzumab as a treatment for patients suffering from metastatic or advanced unresectable HER2-positive breast cancer, or those patients with brain metastases, who have previously received one or more anti-HER2-based treatments in the metastatic settings [94]. The gene discussed is ERBB2; the disease is breast cancer.