LAUSR

The safety of osimertinib is limited in patients with severe or moderate renal impairment, or low body weight. This study aimed to investigate the safety, pharmacokinetics (PK) and recommended dose (RD) of osimertinib in patients with epidermal growth factor receptor (EGFR)‐mutated non–small cell lung cancer (NSCLC) with impaired renal function and low body weight. Thirty‐one eligible patients were enrolled and allocated into four cohorts: A, normal renal function (estimated glomerular filtration rate [eGFR] ≥ 50 mL/min/1.73 m2) and normal body weight (≥45 kg); B, moderate renal impairment (eGFR = 30‐50 mL/min/1.73 m2); C, low body weight (<45 kg); and D, severe renal impairment (eGFR <30 mL/min/1.73 m2 or undergoing dialysis). PK parameters and safety were evaluated with a starting dose of 80 mg osimertinib administered orally once daily in cohorts A, B, and C and 40 mg once daily in cohort D. The PK parameters in cohorts A, B, and C were found to be similar. No dose‐limiting toxicity was observed, and the RD was determined to be 80 mg once daily in patients with moderate renal function and low body weight. Four serious adverse events, acneiform rash, diarrhea, QTc prolongation, and interstitial lung disease, were noted. Although the PK parameters of osimertinib were similar across all cohorts, toxicity occurred more frequently in patients with impaired renal function and low body weight. Clinicians should prescribe osimertinib with caution in NSCLC patients with impaired renal function and low body weight.