Inclusion Criteria:

          1. Subjects must be ≥ 18 years of age at the time of screening.

          2. Subjects must have a confirmed diagnosis of relapsed/refractory MM as per IMWG
             criteria (Rajkumar et al, 2014) and have exhausted standard of care regimens with
             proven clinical benefit, which include agents from the following anti myeloma
             therapies: PIs, IMIDs, and mAbs and have measurable disease with at least one of the
             following criteria:

               1. Serum M-protein ≥ 0.5 g/dL

               2. Urine M-protein ≥ 200 mg/24 hours

               3. Serum free light chain (FLC) assay: involved FLC level ≥ 10 mg/dL provided serum
                  FLC ratio is abnormal.

          3. Subjects must either be ineligible for or post-autologous stem cell transplant.

          4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1.

          5. Adequate organ and marrow functions as determined per protocol-defined criteria.

        Exclusion Criteria

        Any of the following would exclude the subject from participation in the study:

        Target Disease:

          1. Subjects who have previously received an autologous stem cell transplant if less than
             90 days have elapsed from the time of transplant or the subject has not recovered from
             transplant associated toxicities prior to the first scheduled dose of MEDI2228

          2. Subjects who have previously received an allogeneic stem cell transplant

          3. Central nervous system (CNS) involvement(including meningeal involvement) by MRI or
             cerebrospinal fluid exam

          4. Known history of polyneuropathy, organomegaly, endocrinopathy, monoclonal protein,
             skin changes (POEMS) syndrome, plasma cell leukemia, Waldenstrom's macroglobulinemia,
             or amyloidosis

             Medical History and Concurrent Diseases:

          5. Any condition that, in the opinion of the investigator, would interfere with
             evaluation of the investigational product or interpretation of subject safety or study
             results