Study to Investigate Petosemtamab in Adults With Metastatic Non-Small Cell Lung Cancer

This study is testing petosemtamab, a new type of targeted drug, combined with pembrolizumab (an established immunotherapy) as a first-line treatment for people with advanced, metastatic non-small cell lung cancer (NSCLC) that has not yet been treated. The study focuses on people whose tumors have high PD-L1 expression, which may make them more responsive to immunotherapy. **You may be eligible if:** - You are 18 or older with a confirmed diagnosis of metastatic (stage IV) non-small cell lung cancer - Your tumor has high PD-L1 expression (TPS ≥ 50%) - You have at least one measurable tumor on imaging scans - You have not received any prior treatment for your metastatic cancer - Your general health is good (ECOG performance status 0 or 1) - Your blood counts, kidney, and liver function are adequate **You may NOT be eligible if:** - You have untreated brain metastases or cancer spreading to the lining of the brain - You have previously received immunotherapy (PD-1/PD-L1 inhibitors) or chemotherapy for metastatic disease - You have had recent major surgery or radiation therapy - You have uncontrolled heart failure, recent heart attack, or serious heart arrhythmia - You have a lung condition such as pulmonary fibrosis or interstitial lung disease - You have an active serious infection or known infectious disease - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.