Dose Escalation Study of I-131-CLR1404 in Patients With Relapsed or Refractory Multiple Myeloma

Inclusion Criteria: * Histologically or cytologically confirmed multiple myeloma * Prior treatment with or intolerance to proteasome inhibitor and immunomodulator * Bone marrow biopsy within 28 days of study drug infusion demonstrating at least 5% plasma cell involvement * Progressive disease defined by any of following: 25% increase in serum M-protein from lowest response value during (or after) last therapy and/or absolute increase in serum M-protein of \> or equal to 0.5 g/dL; 25% increase in urine M-protein from lowest response value during (or after) last therapy and/or absolute increase in urine M-protein of \> or equal to 200 mg/24h; 25% increase in bone marrow plasma cell percentage from lowest response value during (or after) last therapy - absolute bone marrow plasma cell percentage must be \> or equal to 10% unless prior complete response when absolute bone marrow plasma cell percentage must be \> or equal to 5%; 25% increase in serum FLC level from the lowest response value during (or after) last therapy - the absolute increase must be \> 10 mg/dL; new onset hypercalcemia \> 11.5 mg/dL * Measurable disease defined by any of following: Serum M-protein \> 1 g/dL; Urine M-protein \> 200 mg/24h; Serum free light chain (FLC) assay: involved FLC level \> or equal to 10 mg/dL provided serum FLC ratio is abnormal; subjects who are non-secretors will be considered on a case-by-case basis * Eastern Cooperative Oncology Group performance status of 0 to 2 * Life expectancy of at least 6 months * Have initiative and means to be compliant with protocol and within geographical proximity to make required study visits as judged by Investigator * Subject or legal representative has ability to read, understand and provide written informed consent for study related procedures * Women of childbearing potential must have negative pregnancy test within 24 hours of enrollment * Women of childbearing potential and men who are able to father a child, must agree to use an effective contraception method during study and for 12 months following study drug administration Exclusion Criteria: * Grade 2 or greater toxicities due to previous therapies, subject to laboratory abnormalities listed below. Stable, tolerable Grade 2 adverse events may be allowed at discretion of Investigator * Prior external beam radiation therapy resulting in greater than 20% total bone marrow receiving greater than 20 Gy * Prior radioisotope therapy * Prior total body or hemi-body irradiation * Extradural tumor in contact with the spinal cord or tumor located where swelling in response to therapy may impinge upon spinal cord * Subject has any of following laboratory abnormalities: WBC \< 3000/uL; ANC \< 1500/uL; Hemoglobin \< 8 g/dL; Estimated glomerular filtration rate \< 30 mL/min/1.73 m2; ALT \> 3 x ULN ; Bilirubin \> 1.5 x ULN * Platelet count \< 100,000/uL without full-dose anticogulation therapy * Platelet count \< 150,000/uL with ongoing full-dose anticoagulation therapy * Clinically significant bleeding event, as judged by investigator, within prior 6 months * Chronic immunosuppressive therapy * Anti-platelet therapy, except low-dose aspirin for cardioprotection * PTT \> 1.3 x ULN * INR \> 1.3 * Radiation therapy, chemotherapy, immunotherapy, investigational therapy or corticosteroid use within 2 weeks of or after eligibility-defining bone marrow biopsy. Bisphosphonates and denosumab are permitted if subject has been receiving for at least 90 days * History of hypersensitivity to iodine * Any other concomitant serious illness or organ system dysfunction in opinion of Investigator would either compromise subject safety or interfere with test drug safety evaluation * Major surgery within 6 weeks of enrollment * Known history of HIV, hepatitis C or hepatitis B infection * Pregnancy or breast-feeding