Advanced Non-small Cell Lung Cancer, HER2 Mutation

Researchers are looking for a better way to treat people who have advanced non-small cell lung cancer (NSCLC) with specific genetic changes called human epidermal growth factor receptor 2 (HER2) mutations. Advanced NSCLC means lung cancer that has spread nearby or to other parts of the body or is unlikely to be controlled with current treatments. HER2 is a protein that helps cells to grow and divide. Sometimes, cancer cells have a damaged HER2 gene. This is called a mutation. This mutation can lead to an abnormal HER2 protein which may cause cancer cells to grow and divide too quickly. The study treatment, sevabertinib, is designed to block the mutated HER2 protein and may help slow or stop the cancer from growing. The main purpose of this study is to find out how well sevabertinib works and how safe it is, compared with standard treatment in participants with advanced NSCLC with a HER2 mutation. The study participants will receive one of the study treatments: * Sevabertinib as a tablet taken by mouth twice a day * Standard approved treatment for this condition given by infusion into a vein every 21 days Participants will continue their assigned treatment for as long as they benefit from it and do not experience severe side effects, or until they or their doctor decide to stop treatment. When a participant assigned to the standard treatment has their cancer gets worse, they may have the opportunity to switch to receive sevabertinib. This switch is called a crossover. Participants who switch to sevabertinib will continue this treatment until their disease gets worse again, they have side effects that are too severe, or they or their doctor decide to stop treatment. During the study, the research team will: * do scans such as CT, PET, MRI, or X-rays to check the cancer * Check the overall health of the participants by performing tests such as blood and urine tests and checking heart health using an electrocardiogram and echocardiogram. * do pregnancy tests when needed * ask how the participants are feeling and whether they have had any adverse events or other health problems An adverse event is any medical problem that a participant has during a study. Doctors keep track of all adverse events, irrespective if they think it is related or not to the study treatment.