ERBB2 and breast cancer: This mutation is a common indicator of poor prognosis and is also the most commonly mutated gene in hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. During its trial, ketoacidosis was reported in only 0.7% of patients, with the more common side effects (>20%) being diarrhea (58%), rash (52%), nausea (45%), fatigue (42%), decreased appetite (36%), stomatitis (30%), vomiting (27%), weight loss (27%), and alopecia (20%).