A phase 2, open-label, multicenter study of the long-term safety of siltuximab (an anti-interleukin-6 monoclonal antibody) in patients with multicentric Castleman disease

Oncotarget. 2015 Oct 6;6(30):30408-19. doi: 10.18632/oncotarget.4655.


Background: Multicentric Castleman disease (MCD) is a rare, systemic lymphoproliferative disorder driven by interleukin (IL)-6 overproduction. Siltuximab, an anti-IL-6 monoclonal antibody, has demonstrated durable tumor and symptomatic responses in a multinational, randomized, placebo-controlled study of MCD.

Methods: This preplanned safety analysis was conducted to evaluate the long-term safety of siltuximab treatment among 19 patients with MCD who had stable disease or better and were enrolled in a phase-1 study and subsequent ongoing, open-label, phase-2 extension study. Dosing was 11 mg/kg administered intravenously every 3 weeks, per protocol, or every 6 weeks at the investigator's discretion. Safety monitoring focused on potential risks associated with the anti-IL-6 mechanism of action. Investigator-assessed disease control status was also documented.

Results: Median treatment duration for the 19 patients was 5.1 (range 3.4, 7.2) years, with 14 (74%) patients treated for >4 years. Grade-≥ 3 adverse events (AEs) reported in >1 patient included hypertension (n = 3) and nausea, cellulitis, and fatigue (n = 2 each). Grade-≥ 3 AEs at least possibly attributed to siltuximab were leukopenia, lymphopenia, and a serious AE of polycythemia (n = 1 each). Hypertriglyceridemia and hypercholesterolemia (total cholesterol) were reported in 8 and 9 patients, respectively. No disease relapses were observed, and 8 of 19 patients were able to switch to an every-6-week dosing schedule.

Conclusions: All MCD patients in this extension study have received siltuximab for a prolonged duration (up to 7 years) without evidence of cumulative toxicity or treatment discontinuations and with few serious infections. All patients are alive, demonstrate sustained disease control, and continue to receive siltuximab.

Keywords: clinical trial; interleukin-6; multi-centric Castleman's disease; siltuximab.

Publication types

  • Clinical Trial, Phase II
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Antibodies, Monoclonal / administration & dosage
  • Antibodies, Monoclonal / adverse effects
  • Antibodies, Monoclonal / therapeutic use*
  • Antineoplastic Agents / administration & dosage
  • Antineoplastic Agents / adverse effects
  • Antineoplastic Agents / therapeutic use*
  • Castleman Disease / drug therapy*
  • Castleman Disease / pathology
  • Disease-Free Survival
  • Drug Administration Schedule
  • Female
  • Humans
  • Infusions, Intravenous
  • Male
  • Middle Aged
  • Time Factors
  • Treatment Outcome
  • United States
  • Young Adult


  • Antibodies, Monoclonal
  • Antineoplastic Agents
  • siltuximab

Supplementary concepts

  • Multi-centric Castleman's Disease