Additional Study Information: The purpose of this study is to learn more about an investigational drug called savolitinib in combination with osimertinib for the treatment of non-small cell lung cancer (NSCLC) compared to platinum-based doublet chemotherapy (a standard of care treatment). Participants will be randomly assigned to one of two study groups at the beginning of this study. This means participants will be assigned to a study group by chance, like flipping a coin or rolling dice. Investigational means that the drug is not approved by any health authority, except for use in research studies like this. People who have this usually have standard chemotherapy treatment. Chemotherapy works by targeting cancer cells that grow, multiply and divide quickly. Osimertinib is approved by health authorities for the treatment of NSCLC when the patient has a particular mutation in EGFR in their cancer. Osimertinib is known to work well initially when they have this particular mutation in their cancer, but resistance often occurs after several months of treatment. Osimertinib targets mutated forms of epidermal growth factor receptor (EGFR). Savolitinib works by targeting a protein called mesenchymal epithelial transition (MET), a protein that is involved in sending signals within cells and in cell growth and survival. Both osimertinib and savolitinib work to block the action of abnormal proteins that signal cancer cells to multiply.