Inclusion criteria 1. Diagnosis of MM requiring systemic therapy (34): 2. Age ≥ 18 years. 3. ECOG performance status (0-2). 4. Life expectancy > 3 months. 5. Relapsed or refractory to two or more different prior therapies, Exclusion criteria 1. Plasma cell leukemia . 2. Known amyloidosis 3. Patients who previously have received an allogeneic stem cell transplant and receive or have received immunosuppressive therapy within the last three months. or Patients who previously have received an allogeneic stem cell transplant and have signs of acute or chronic graft-versus-host disease. 4. Sensory or motor neuropathy ≥ grade 3. 5. Past or current malignancy, 6. Chronic or ongoing active infectious disease 7. Clinically significant cardiac disease 8. Significant concurrent, uncontrolled medical condition including, but not limited to, renal (except related to MM), hepatic, hematological except MM, gastrointestinal, endocrine, pulmonary, neurological, cerebral or psychiatric disease. 9. Patients with baseline QTcF > 470 ms, as well as those with complete left bundle branch block (defined as a QRS ≥ 120 ms in left bundle branch block form). 10. Hypokalemia 11. Clinical signs of meningeal involvement of MM. 12. Known severe chronic obstructive pulmonary disease or asthma defined as FEV1< 60% of expected. 13. History of significant cerebrovascular disease. 14. Known Human Immunodeficiency Virus seropositivity. 15. Positive serology for hepatitis B 16. Screening laboratory values 17. Concomitant corticosteroid 18. Other chemotherapy that is or may be active against myeloma within 3 weeks prior to Visit 2.