This study is an open-label (both physician and patient know the name of the study drug), multicenter (more than one site) study of siltuximab in patients with relapsed or refractory multiple myeloma receiving siltuximab in combination with bortezomib/dexamethasone to evaluate the safety, pharmacokinetics (how drugs are absorbed in the body, how they are distributed within the body and how they are removed from the body over time), efficacy and immunogenicity (the ability to induce immune responses). This study is planned with a dose escalation of siltuximab to levels of 5.5 mg/kg (Dose Level 1) and 11.0 mg/kg (Dose Level 2) given intravenously. Recommended doses will be determined based on the incidence of dose-limiting toxicity in patients with relapsed or refractory multiple myeloma when siltuximab at dose levels of 5.5 mg/kg and 11.0 mg/kg is administered with bortezomib/dexamethasone. Treatment with siltuximab will be started at Dose Level 1, and treatment at Dose Level 2 will not be started until completing the safety evaluation at the end of the observation period of Cycle 1 for all patients at Dose level 1. Once 11.0 mg/kg is determined as a recommended dose, the dose for patients whose starting dose is 5.5 mg/kg, and who have not achieved complete response, can be escalated to 11.0 mg/kg based on patient consent and investigator discretion in the next cycle. Siltuximab will be given at 5.5 or 11.0 mg/kg by intravenous infusion over 1 hour on Day 1 of each 21-day cycle until progression. Twice-weekly intravenous administration of bortezomib 1.3 mg/m2 (Days 1, 4, 8, and 11) will be followed by a 10-day rest period (Days 12-21). Four-per-week oral administration of dexamethasone 20 mg (Days 1, 2, 4, 5, 8, 9, 11 and 12) will be followed by a 9-day rest period (Days 13-21).
The purpose of this study is to assess the safety and the tolerability of siltuximab up to 11.0 mg/kg in combination with bortezomib and dexamethasone for patients with relapsed or refractory multiple myeloma.