Study of Ifinatamab Deruxtecan (DS-7300a, I-DXd) in Participants With Advanced Solid Malignant Tumors

This is a single group study of participants with advanced solid tumors who have not been cured by other treatments. It is the first time the drug will be used in humans, and will be in two parts. The primary purpose of the parts are: * Dose Escalation Part: To evaluate the safety and tolerability and to determine the maximum tolerated dose and the recommended dose for expansion of ifinatamab deruxtecan (I-DXd). * Dose Expansion Part: To investigate the safety, tolerability and antitumor activity of I-DXd when administered as a single agent. This study is expected to last approximately 5 years from the time the first participant is enrolled to the time the last participant is off the study. The number of treatment cycles is not fixed in this study. Participants who continue to benefit from the study treatment may continue, unless: * they withdraw * their disease gets worse * they experience unacceptable side effects.