Researchers are looking for a better way to treat advanced Triple-Negative Breast Cancer (TNBC) and Non-Small-Cell Lung Cancer (NSCLC). "Advanced" usually means that the cancer keeps growing even with treatment. The cancer may also be "metastatic", which means that it has spread to other parts of the body or the surrounding tissue. The study drug, Datopotamab deruxtecan, is designed to work by attaching to the tumor cells and stopping the tumor growth. Datopotamab deruxtecan is also known as Dato-DXd. In this study, the researchers want to find out how well Dato-DXd works to stop tumors from growing in Chinese participants with NCSLC or TNBC. This is the first time Dato-DXd is being studied in Chinese population. Participants in this study will get Dato-DXd through a needle as an injection. They will get 1 dose of Dato-DXd every 3 weeks until their cancer gets worse or they leave the study for another reason. Participants will visit their study sites at least once every 3 weeks for as long as they are in the study. The study doctors will take blood samples every 3 weeks and take images of the participants' tumors every 6 weeks until the participant leaves the study.