6. Prior therapy with carfilzomib is allowed as long as the patient had at least a PR to prior carfilzomib therapy, was not removed from carfilzomib therapy due to toxicity, and had at least a 6-month carfilzomib treatment-free interval from last dose received until first study treatment. (Patients may receive maintenance therapy with drugs that are not in the proteasome inhibitor class during this 6 month carfilzomib treatment-free interval). The exception to this is patients randomized or previously randomized in any other Onyx-Sponsored Phase 3 trial.