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.
