A Study to Determine the Efficacy, Safety and Pharmacokinetics of GMI-1271 as Adjunct to Standard of Care for the Treatment of Multiple Myeloma

Inclusion Criteria: 1. Males and females ≥ 18 years of age 2. Confirmed diagnosis of Multiple Myeloma 3. Subjects with progressive MM who have received at least 1 prior therapy and who have already undergone or are not expected to undergo hematopoietic stem cell transplantation 4. Subjects previously treated with an IMiD-based regimen or ineligible for an IMiD-based treatment regimen 5. Subjects must be receiving treatment with a proteasome inhibitor-based regimen (bortezomib-based or carfilzomib-based) 6. Adequate hepatic, renal, and cardiac function Exclusion Criteria: 1. Intolerant to bortezomib or carfilzomib 2. Progressing evidence of end organ damage attributed to the underlying disease 3. Plasma cell leukemia 4. Congestive heart failure 5. Acute active infection 6. Non-hematologic malignancy within the past 3 years except: a) adequately treated basal cell or squamous cell skin cancer, b) carcinoma in situ of the cervix, or c) prostate cancer with stable PSA 7. Significant peripheral neuropathy