A phase 1b study reveals that combining trastuzumab deruxtecan (T-DXd) with pembrolizumab demonstrates significant antitumor activity in HER2-expressing and HER2-mutant non-small cell lung cancer. The combination achieved particularly impressive results in previously untreated patients, with response rates of 62.5% and 80% in HER2-expressing and HER2-mutant NSCLC respectively.