INTRODUCTION: Zongertinib (BI 1810631) is a potent, selective, and epidermal growth factor receptor (EGFR) wild-type sparing human epidermal growth factor receptor 2 (HER2) inhibitor. Based on in vitro data, the oxidative hepatic metabolism of zongertinib is principally driven by cytochrome P450 (CYP) 3A4/5. Therefore, zongertinib may be affected by strong CYP3A inducers, like carbamazepine. OBJECTIVE: This study aimed to investigate the effect of multiple oral doses of carbamazepine on the pharmacokinetics of a single oral dose of zongertinib in healthy male subjects. METHODS: This open-label, two-period, fixed-sequence clinical drug-drug interaction study examined the pharmacokinetics of a single 60-mg oral dose of zongertinib in the absence or presence of multiple oral doses of carbamazepine. The extent of drug-drug interaction was estimated using the adjusted geometric mean ratios (and 90% confidence intervals [CIs]) for the test treatment (zongertinib in the presence of carbamazepine) versus the reference treatment (zongertinib alone) for areas under the plasma concentration-time curve from time 0 to infinity and to the last quantifiable time point (AUC RESULTS: Sixteen subjects (all Caucasian males) received zongertinib alone in Study Period 1, and 15 of them received both zongertinib and carbamazepine in Study Period 2. Upon co-administration with carbamazepine in Study Period 2, AUC CONCLUSION: Zongertinib exposure was reduced by 63.5% when coadministered with the strong CYP3A inducer, carbamazepine.