The phase 2 DESTINY-Lung02 study compared the 5.4 mg/kg vs. 6.4 mg/kg dosing of T-DXd in HER2-mutant NSCLC patients and confirmed a higher incidence of drug-related pneumonitis with the higher dose: 12.9% vs. 28.0% of patients had reported drug-related pneumonitis (2.0% grade ≥ 3 in each arm) in the 5.4 mg/kg and 6.4 mg/kg groups, respectively [22]. The gene discussed is ERBB2; the disease is pneumonitis.