Proteasome inhibitors and IMiDs have different but overlapping mechanisms of anti-MM activity. In the clinical setting, both proteasome inhibitors and IMiDs enhance the activity of dexamethasone, and synergy has previously been demonstrated between the first in class proteasome inhibitor, bortezomib[16] and the immunomodulatory drug lenalidomide[17]. Relative to bortezomib, carfilzomib demonstrated increased apoptosis in MM cell lines, and induce high ORR in both bortezomib-naïve and resistant patients.