Proteasome inhibitors are used to treat conditions such as multiple myeloma and mantle cell lymphoma. These medications work by blocking proteasomes inside of cancer cells, which helps to kill the cancer cells. Proteasome inhibitors come in different forms, including oral pills and injections. Examples include Velcade (bortezomib), Kyprolis (carfilzomib), and Ninlaro (ixazomib).