The study was stopped after the interim analysis based on lack of sufficient efficacy. There were no safety concerns.

The purpose of this study is to evaluate the efficacy of siltuximab, demonstrated by a reduction in red blood cell (RBC), transfusions to treat the anemia of Myelodysplastic Syndrome (MDS).

The study treatments will be administered double-blind for 12 weeks, meaning that the patient and study personnel will not know the identity of the treatment. Approximately 75 patients will be randomized (patients are assigned to a treatment by a chance) in a 2:1 ratio to receive siltuximab plus best supportive care (BSC) (Group A) or placebo plus BSC (Group B). BSC includes RBC transfusion, antimicrobials, white blood cell (WBC) growth factors, and platelet transfusions. Patients who complete 12 weeks of treatment may qualify to receive siltuximab as open-label (identity of treatment will be known) treatment. Treatment may continue until death, unacceptable toxicity, withdrawal of consent, or the clinical cutoff (defined as 24 weeks after the last patient is randomized), whichever occurs first. The study will end approximately 36 weeks after the last patient is randomized. Patient safety will be monitored. Siltuximab and matching placebo will be supplied as a sterile, lyophilized formulation for reconstitution and intravenous (IV) infusion. Group A: siltuximab (15 mg/kg) administered as a 1-hour infusion every 4 weeks + BSC, or Group B: placebo administered as a 1-hour infusion every 4 weeks + BSC.

Inclusion Criteria:

• Confirmed diagnosis of myelodysplastic syndrome (MDS), according to World Heath Organization or the French-American-British Cooperative Group pathologic classification, with an International Prognostic Scoring System score 0, 0.5, or 1.0, indicating Low- or INT-1-risk disease.
• Documented RBC transfusion of at least 2 units of RBC for the treatment of the anemia of MDS in the 8 weeks preceding the start of the Screening Period.
• Adequate iron stores, demonstrated by either the presence of stainable iron in the bone marrow or a serum ferritin of > 100 ng/mL.
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0 to 2.
• Symptomatic anemia (defined by a score > 0 on the Non-Chemotherapy Anemia Symptom Scale [NCA-SS]).

Exclusion Criteria:

• Had treatment with drugs or other agents targeting IL-6 or its receptor within 4 weeks of randomization.
• Any condition that, in the opinion of the investigator, would make participation not in the best interest (eg, compromise the well-being) of the patient or that could prevent, limit, or confound the protocol-specified assessments.
• Patients with Chronic Myelomonocytic Leukemia (CMML).
• Causes other than MDS contributing to anemia, such as Vitamin B12 or folate deficiency, bleeding, hemolysis, hemoglobinopathy, or chronic renal failure.