 This trial will evaluate the efficacy and safety of combination of pomalidomide POM and low-dose dexamethasone LD-Dex Cohort A or the combination of pomalidomide POM , daratumumab DARA and low-dose dexamethasone LD-Dex Cohort B in subjects with relapsed or refractory multiple myeloma who have received a first or second line treatment of lenalidomide-based therapy. 