All participants will be asked to take either ixazomib plus dexamethasone (in cases where only 4 mg tablets for dexamethasone are available, the following dexamethasone schedule is recommended for participants aged ≥75 years: 12 mg dexamethasone will be given on Days 1, 8, 15, and 22 of every 28-day cycle; and 8 mg dexamethasone will be given on Days 2, 9, 16, and 23 of every 28-day cycle) or pomalidomide 4 mg + dexamethasone 40 mg at recommended doses.