Grade 3 AEs related to T-DXd therapy consisted of fatigue (20%; 3 patients), one case of anemia, neutropenia, alanine aminotransferase increase, aspartate aminotransferase increase, diarrhea, dyspnea, left ventricular systolic dysfunction (LVSD), gamma-glutamyltransferase increase, and urinary tract infection, respectively. The gene discussed is GPT; the disease is urinary tract infection.