The drug being tested in this study is called Ixazomib. Ixazomib is being tested to treat people who have relapsed and/or refractory multiple myeloma (RRMM). This study will look at progression free survival (PFS), overall survival (OS) and safety in participants who take ixazomib in addition to lenalidomide and dexamethasone compared to placebo in addition to lenalidomide and dexamethasone.