The primary purpose of the Phase II portion of the study is to assess whether the combination of pomalidomide/dexamethasone/ixazomib improves progression free survival relative to pomalidomide/dexamethasone. Please see the "Arms" section below for a detailed description of the treatment arms for Phase II of the study. The dose for pomalidomide and ixazomib will be determined in phase I of the study. About 108 patients will take part in this portion of the study. The secondary objectives are listed below.