The following criteria is provided for health care professionals.

Key Inclusion Criteria:

1. Previously diagnosed with MM requiring treatment based on IMWG diagnostic criteria;
2. Relapsed or refractory MM after adequate exposure to and therapeutic response (following IMWG response criteria) to at least one line of treatment with one or more active agents, including alkylating drugs, corticosteroids, immunomodulatory drugs (IMiD: thalidomide, lenalidomide, pomalidomide), proteasome inhibitors (bortezomib, cartilzomib), and monoclonal antibodies (daratumumab, elotuzumab, ixazomab);
3. Evaluable MM with at least one of the following: (a) serum monoclonal component ≥ 1 g/dL IgG or ≥ 0.5 g/dL IgA; or (b) Bence-Jones (BJ) proteinuria ≥ 200 mg/24h; or (c) measurable plasmacytoma (not previously irradiated); or (d) involved serum free light chain ≥ 10 mg/dL, with an abnormal free light chain ratio;
4. ECOG Performance Status (PS) 0-2;
5. Life expectancy > 3 months;
6. At least 2 weeks (or 5 half-lives, whichever is longer) wash-out since the end of previously administered experimental therapy (6 weeks if previous nitrosourea containing regimen) or 2 weeks for standard-of-care regimens. Concurrent corticosteroids are allowed provided they are administered at an equivalent prednisone dose of ≤ 10 mg/day, as prediction or blood products only;
7. Recovery from non-hematologic toxic effects of prior therapy to grade ≤ 1 (except alopecia) by NCI CTCAE Version 4.03;
8. Adequate bone marrow (BM), renal, hepatic and metabolic function.

Key Exclusion Criteria:

1. Any of the following concomitant diseases/conditions:
   • History or presence of myocardial infarction, clinically relevant valvular heart disease, or congestive heart failure within the last 12 months;
   • Unstable cardiac dysrhythmias or persistent prolongation of the corrected QT interval (QTc) (Fridericia) to >450 msec for males or >470 msec for females, based on ECG at screening (patients with stable atrial fibrillation on treatment are allowed provided they do not meet any other cardiac or prohibited drug exclusion criterion);
   • Presence of current angina;
   • Active uncontrolled infection;
   • Morphological or cytological features of myelodysplasia and/or post-chemotherapy aplasia on BM assessment;
   • Myopathy > grade 2 or any clinical situation that causes significant and persistent elevation of CPK (>2.5 x ULN in two different determinations performed one week apart);
   • Peripheral neuropathy > grade 1;
   • POEMS syndrome or active plasma cell leukemia;
   • Chronic graft versus host disease (GVHD) or on immunosuppressive therapy for the control of GVHD;
   • Uncontrolled leptomeningeal disease;
   • Uncontrolled disease-related metabolic disorder (e.g., hypercalcemia);
   • Known human immunodeficiency virus (HIV) infection (HIV testing is not required unless infection is clinically suspected);
   • Known active hepatitis B or C virus (HBV or HCV) infection;
   • Limitation of the patient's ability to comply with treatment or follow-up requirements; and
   • Any other major illness that, in the Investigator's judgment, may substantially increase the risk associated with the patient's participation in this study;
2. History of prior malignancy other than those previously treated with a curative intent more than 5 years ago and without relapse (any tumor) or basal cell skin cancer, in situ cervical cancer, superficial bladder cancer, or high grade intestinal polyps treated adequately, regardless of the disease-free interval;
3. Prior irradiation to > 30% of BM reserves (including total body irradiation), regardless of the washout period;
4. High dose chemotherapy followed by autologous stem cell transplantation within 90 days prior to initiating study treatment;
5. Bisphosphonate treatment within 7 days prior to initiating study treatment (while on study, bisphosphonates can be administered only once a month, between Days 18 to 21 of the 28-day treatment cycle)