Inclusion Criteria:

• Confirmed relapsed or refractory MM or PCL. Patients should have received at least two prior treatment regimens. Prior treatment must have included bortezomib and an immunomodulatory agent (e.g., thalidomide and/or lenalidomide), unless patients were not eligible or refused to receive these treatments. The disease should have progressed during or after the last prior treatment regimen.

• Measurable MM disease, defined as one of the following:

  • A monoclonal immunoglobulin (Ig) concentration on serum electrophoresis of ≥ 1.0 g/dL for an IgG myeloma, 0.5 g/dL for an IgA myeloma, and 0.1 g/dL for an IgD myeloma;
  • Measurable urinary light chain secretion by quantitative analysis of ≥ 200 mg/24 hours;
  • Involved serum free light chain (FLC) level ≥ 10 mg/dL, provided the serum FLC ratio is abnormal;
  • Patients with oligo- or non-secretory disease must have bone marrow involvement with at least 30% plasmacytosis on aspiration.
• Male or female, ≥ 18 years of age at time of signing consent.
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1.

• Adequate hematology laboratory values without transfusion support within two weeks of screening:

  • Hemoglobin ≥ 8 g/dL;
  • Absolute neutrophil count (ANC) ≥ 1.5 x 109/L;
  • Platelets ≥ 75 x 109/L.

• Adequate liver and renal function:

  • Aspartate aminotransferase (AST)/serum glutamic oxaloacetic transaminase (SGOT) and/or alanine aminotransferase (ALT)/serum glutamic pyruvic transaminase (SGPT) ≤ 2.5 x the upper limit of normal (ULN);
  • Bilirubin < 1.5 mg/dL;
  • Serum creatinine ≤ 2.5 mg/dL, and a calculated creatinine clearance of at least 50 mL/min (using the Cockcroft and Gault method).
• If patient is female and of childbearing potential, she must have a negative serum beta human chorionic gonadotropin (ß HCG) test.
• Male patients and female patients of childbearing potential must agree to use an effective method of contraception per institutional standard.
• Signed informed consent prior to initiation of any study-related procedures that are not considered standard of care.

Exclusion Criteria:

• Primary amyloidosis.
• Concomitant malignancies or previous malignancies with less than a three-year disease free interval at the time of enrollment. Patients with adequately resected basal or squamous cell carcinoma of the skin, carcinoma in situ of the cervix or Stage A low grade prostate cancer may enroll irrespective of the time of diagnosis.
• Autologous or allogeneic stem cell or bone marrow transplant within 3 months prior to first dose of study drug.
• Treatment with an investigational product or device within 28 days of initiating study drug.
• Cytotoxic therapy or monoclonal antibodies within 21 days prior to first dose of study drug.
• Radiotherapy within 21 days prior to first dose of study drug. However, if the radiation portal covered ≤ 5% of the bone marrow reserve, the patient may be enrolled irrespective of the end date of radiotherapy.
• Major surgery within two weeks prior to first dose of study drug.
• Corticosteroid doses > 10 mg/day within two weeks prior to first dose of study drug.
• Any serious medical or psychiatric disorder that would interfere with patient safety or informed consent.
• Any severe concurrent disease or condition (including active systemic infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia), which, in the judgment of the Investigator, would make the patient inappropriate for study participation.
• Known positive serology for the Human Immunodeficiency Virus (HIV), Hepatitis B and/or active Hepatitis C.