The drug being tested in this study is called TAK-573. TAK-573 is being tested to treat participants who have refractory MM. The study consists of 2 Phases, 1 and 2a. The study will enroll approximately 51 and 18 participants in Phase 1 and 2a respectively. Participants will be randomly assigned (by chance, like flipping a coin) to one of the following treatment groups in each Phase: