MEDI-551 as Maintenance Therapy After Allogeneic Stem Cell Transplant in Multiple Myeloma

Inclusion Criteria: 1. Previous diagnosis of MM based on standard criteria as defined in Appendix A (Diagnostic Criteria for MM). Diagnostic studies need not be performed within 30 days of registration; 2. Patients must meet one of the disease criteria outlined in either a, b, or c: a. Patients with newly diagnosed high-risk MM achieving a partial response (PR) or better at the time of enrollment in response to systemic anti-myeloma therapy, which may include autologous hematopoietic stem cell transplant (HSCT). High risk is defined by the presence of any one of the following: i. High-risk chromosomal translocations by fluorescent in situ hybridization (FISH): t(4;14), t(14;16), t(14;20), del(17p), del(1p), amplification 1q ii. Myeloma Prognostic Risk Signature 70-Gene expression profiling (MyPRS GEP-70) high-risk signature either at diagnosis or at time of registration for the study iii. Lactate dehydrogenase (LDH) \> 300 U/L at diagnosis iv. Plasma cell leukemia v. Relapse from prior therapy within 12 months b. Patients with high-risk MM with at least 1 prior progression in PR or better in response to salvage systemic anti-myeloma therapy at the time of enrollment c. Patients with standard risk MM with 1 prior progression within 18 months from an autologous HSCT and in very good partial remission (VGPR) or better in response to salvage systemic anti-myeloma therapy at the time of enrollment. 3. Patients must have a suitable first-degree or second-degree related, Human leukocyte antigen (HLA)-haploidentical or HLA-matched stem cell donor. The donor and recipient must be identical at least one allele of each of the following genetic loci: HLA-A, HLA-B, HLA-Cw, major histocompatibility complex, class II, DR beta 1 (HLA-DRB1), and Major Histocompatibility Complex, Class II, DQ Beta 1 (HLA-DQB1). A minimum match of 5/10 is therefore required, and will be considered sufficient evidence that the donor and recipient share one HLA haplotype; 4. No previous AlloSCT (syngeneic HSCT permissible); 5. Any previous autologous HSCT must have occurred at least 3 months prior to start of conditioning; 6. Eastern Cooperative Oncology Group (ECOG) performance status of 0-2; 7. Life expectancy \> 6 months; 8. Adequate end organ function as measured by: 1. Left ventricular ejection fraction ≥ 35% or shortening fraction \> 25% 2. Bilirubin ≤ 3.0 mg/dL (unless due to Gilbert's syndrome or hemolysis), and alanine aminotransferase (ALT) and aspartate transaminase (AST) \< 5x upper limit of normal (ULN) 3. Forced expiratory volume at one second (FEV1) and forced vital capacity (FVC) \> 40% of predicted 9. Not pregnant or breast-feeding; 10. No uncontrolled infection. Note: Infection is permitted if there is evidence of response to medication; 11. The patient must be able to comprehend and have signed the informed consent. Exclusion Criteria: 1. Diagnosis of any of the following cancers: 1. POEMS syndrome (plasma cell dyscrasia with polyneuropathy, organomegaly, endocrinopathy, monoclonal protein (M-protein) and skin changes) 2. Non-secretory myeloma (no measurable protein on Serum Free Lite Assay) 3. HTLV1 / HTLV2 positive 4. Diagnosis of amyloidosis 2. Failed to achieve at least a partial response (PR) to latest therapy; 3. Known history of HIV infection; 4. Systemic infection requiring treatment with antibiotics, antifungal, or antiviral agents within 7 days of registration; 5. History of malignancy other than MM within 5 years of registration, except adequately treated basal or squamous cell skin cancer; 6. History of serious allergy or reaction to any component of the MEDI-551 formulation that would prevent administration; 7. Active hepatitis B as defined by seropositivity for hepatitis B surface antigen or patients with positive hepatitis B core antibody titers. 8. Patients with hepatitis C antibody will be eligible provided that they do not have elevated liver transaminases or other evidence of active hepatitis.