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Proteasome inhibitors are the backbone in the treatment of multiple myeloma with 3 of its representatives (bortezomib, carfilzomib, and ixazomib) having already been approved. There is a different situation altogether in the treatment of amyloid light chain (AL) amyloidosis where owing to the rarity of this entity neither of these drugs has currently gained approval. Amyloid light chain plasma cells are possibly more vulnerable to bortezomib than myeloma plasmocytes because of a slightly distinct mechanism of action, which is described in depth in this manuscript. Bortezomib is highly active and rapidly effective as a single agent and even more potent in combination with dexamethasone and alkylators. Bortezomib-based regimens have become a standard part of the initial treatment of AL amyloidosis in the majority of centers. We have reviewed all available data on bortezomib in various combinations and settings. Carfilzomib seems to be effective but also toxic in these fragile patients with a high rate of cardiac events. Oral ixazomib has shown a surprisingly high efficacy with manageable toxicity and has received the Food and Drug Administration Breakthrough Therapy designation in 2014 for relapsed AL amyloidosis patients. In this review we have comprehensively described the current available knowledge of these 3 proteasome inhibitors and their use in AL amyloidosis.

Monoclonal gammopathy of undetermined significance (MGUS) is a benign condition with an approximate 1% annual risk of symptomatic plasma cell disorder development, mostly to multiple myeloma (MM). We performed genomewide screening of copy-number alterations (CNAs) in 90 MGUS and 33 MM patients using high-density DNA microarrays. We identified CNAs in a smaller proportion of MGUS (65.6%) than in MM (100.0%, P = 1.31 × 10-5 ) and showed median number of CNAs is lower in MGUS (3, range 0-22) than in MM (13, range 4-38, P = 1.82 × 10-10 ). In the MGUS cohort, the most frequent losses were located at 1p (5.6%), 6q (6.7%), 13q (30.0%), 14q (14.4%), 16q (8.9%), 21q (5.6%), and gains at 1q (23.3%), 2p (6.7%), 6p (13.3%), and Xq (7.8%). Hyperdiploidy was detected in 38.9% of MGUS cases, and the most frequent whole chromosome gains were 3 (25.6%), 5 (23.3%), 9 (37.8%), 15 (23.3%), and 19 (32.2%). We also identified CNAs such as 1p, 6q, 8p, 12p, 13q, 16q losses, 1q gain and hypodiploidy, which are potentially associated with an adverse prognosis in MGUS. In summary, we showed that MGUS is similar to MM in that it is a genetically heterogeneous disorder, but overall cytogenetic instability is lower than in MM, which confirms that genetic abnormalities play important role in monoclonal gammopathies.