Of the 41 HER2-overexpressing NSCLC patients enrolled in cohort 1A (evaluating 5.4 mg/kg of T-DXd), only 7.3% were found to have pneumonitis, with 4.9% grade 3 or higher events (including two deaths), suggesting a possible dose-related effect contributing to the development of adverse events like pneumonitis. The gene discussed is ERBB2; the disease is pneumonitis.