Inclusion Criteria:

- Male or female patients 18 years or older

- Biopsy-proven systemic relapsed or refractory light-chain (AL) amyloidosis, which
after at least 1 prior therapy, in the investigator's opinion, requires further
treatment

- If received stem cell transplant, must be at least 3 months posttransplantation and
recovered from side effects

- Must have measurable disease defined as serum differential free light chain
concentration ≥ 40mg/L

- Must have objective measurable organ (heart or kidney) amyloid involvement

- Must have cardiac biomarker risk stage I or II disease

- Must have adequate hematologic, hepatic, and renal function

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2

- Female patients who are post menopausal, surgically sterile, or agree to practice 2
effective methods of contraception or agree to abstain from heterosexual intercourse

- Male patients who agree to practice effective barrier contraception or agree to
abstain from heterosexual intercourse

- Voluntary written consent

Exclusion Criteria

- Peripheral neuropathy that is greater or equal to Grade 2

- Cardiac status as described in protocol

- Severe diarrhea (≥ Grade 3) not controllable with medication or requires
administration of total parenteral nutrition

- Known gastrointestinal condition or procedure that could interfere with swallowing or
the oral absorption of tolerance of MLN9708

- Uncontrolled infection requiring systematic antibiotics

- Known human immunodeficiency virus (HIV) positive, hepatitis B surface
antigen-positive status, or known or suspected active hepatitis C infection

- Presence of other active malignancy with the exception of nonmelanoma skin cancer,
cervical cancer, treated early-stage prostate cancer provided that prostate-specific
antigen is within normal limit, or any completely resected carcinoma in situ

- Female patients who are lactating or pregnant

- Major surgery within 14 days before the first dose of study drug

- Serious medical or psychiatric illness that could, in the investigator's opinion,
potentially interfere with the completion of treatment according to the protocol