Venetoclax, MLN9708 and Dexamethasone for Relapsed or Refractory Light Chain Amyloidosis

This study is being done to answer the following question: What is the dose of venetoclax, MLN9708 (ixazomib citrate), and dexamethasone in combination that can be safely and tolerably taken by patients with amyloidosis? We are doing this study because we want to find out if this approach is better or worse than the usual approach for amyloidosis. The usual approach is defined as care most people get for amyloidosis.