Inclusion Criteria:

- Male or female subjects ≥ 18 years of age

- Relapsed or refractory multiple myeloma defined as: Failure of at least 2 previous
therapies including an immunomodulatory agent (thalidomide or lenalidomide) and a
proteasome inhibitor (unless the subjects were not eligible or refused to receive
those treatments), and with progressive disease, defined by an increase of
serological or urine myeloma parameters by 25% to the last value

- Presence of serum M-protein ≥ 1 g per 100 mL (≥ 10 g/L) and/or urine M-protein ≥ 200
mg per 24-hour period and/or serum FLCs ≥ 10 mg per 100 mL (≥ 100 mg/L) combined with
an abnormal ratio of lambda and kappa chains

- Life expectancy of > 6 months

- Karnofsky performance status ≥ 60%, Eastern Cooperative Oncology Group (ECOG)
performance status ≤ 2.

- Absolute neutrophil count (ANC) ≥ 1.0 (1,000/mm3) and platelets ≥ 30 × 109/L without
previous transfusion within the last 2 weeks before first study drug administration

- Creatinine clearance ≥ 30 mL/min (calculated using the Cockcroft-Gault equation)

- Total bilirubin ≤ 2 × upper normal limit (UNL)

- Alanine transaminase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 × UNL

- Haemoglobin ≥ 8 g/dL

- If a female of childbearing potential, confirmation of a negative pregnancy test
before enrolment and use of double-barrier contraception, oral contraceptive plus
barrier contraceptive, or confirmation of having undergone clinically documented
total hysterectomy and/or oophorectomy, tubal ligation

- If a male, use of an effective barrier method of contraception during the study and
for 3 months after the last dose if sexually active with a female of childbearing
potential

- Ability to comply with all study-related procedures, medication use, and evaluations

- Ability to understand and give written informed consent, and comply with the protocol

Exclusion Criteria:

- Primary refractory multiple myeloma

- Previous treatment with cytotoxic chemotherapy or large-field radiotherapy or other
myeloma-specific therapy within 28 days prior to the screening visit (radiation to a
single site as concurrent therapy is allowed)

- Treatment with a systemic investigational agent within 28 days prior to the screening
visit

- Hypercalcemia (> 2.7 mmol/L)

- Extramedullary plasmocytoma not originating from bone or plasma cell leukaemia

- Previous allogenic stem cell transplantation

- Known or suspected hypersensitivity to the excipients contained in the study drug
formulation

- Significant uncontrolled cardiovascular disease or cardiac insufficiency (New York
Heart Association (NYHA) classes III-IV)

- Prior therapy with other monoclonal antibodies

- Clinical or laboratory evidence of active hepatitis B (positive HBsAg with negative
HBsAb) or hepatitis C (positive hepatitis c virus antibody and detectable hepatitis C
virus RNA with ALT above the normal range)

- Positive HIV test result (ELISA or Western blot)

- History of ischemic colitis, stroke or myocardial infarction within the last 6 months

- Presence of diarrhoea of grade 2 or higher

- Any active uncontrolled systemic infection

- Any antibiotic therapy due to infections 2 weeks prior to first study drug
administration

- Regular dose of corticosteroids during the 2 weeks prior to study entry or
anticipated need of corticosteroids exceeding prednisone 20 mg/day or equivalent, or
any other immunosuppressive therapy within 2 weeks prior to study entry.

- Major surgery ≤ 4 weeks prior to first study drug administration or ongoing side
effects of such surgery

- Systemic diseases (cardiovascular, renal, hepatic, etc) that would prevent study
treatment

- Multiple myeloma with central nervous system involvement.

- Second active malignant disease, currently requiring treatment (with the exception of
basal cell carcinoma of the skin or curative surgery treated tumours).

- Pregnancy or breastfeeding in women and women of childbearing potential not using an
acceptable method of birth control

- others