Interleukin‐6 (IL‐6) is associated with prostate cancer morbidity. In several experimental models, IL‐6 has been reported to have anti‐apoptotic and pro‐angiogenic effects. Siltuximab (CNTO 328) is a monoclonal anti‐IL‐6 antibody which has been successfully applied in several models representing prostate cancer. This study was designed to assess preliminary safety of siltuximab in patients with early prostate cancer.

Twenty patients scheduled to undergo radical prostatectomy received either no drug or siltuximab (6 mg/kg, five patients per group with administration once, two times, and three times prior to surgery). Blood samples were collected for pharmacokinetic and pharmacodynamic analyses. Expression of elements of IL‐6 signaling pathways was analyzed in tumor tissue by immunohistochemistry. Gene analysis in tumor specimens was performed with the DASL array.

No adverse events related to siltuximab were observed. Patients treated with siltuximab presented with higher levels of proliferation and apoptosis markers. Following a single dose, serum concentrations of siltuximab declined in a biexponential manner. This study revealed a decrease in phosphorylation of Stat3 and p44/p42 mitogen‐activated protein kinases. In addition, gene expression analyses indicate down‐regulation of genes immediately downstream of the IL‐6 signaling pathway and key enzymes of the androgen signaling pathway.

Preliminary safety of siltuximab is favorable. Future studies in which siltuximab could be combined with androgen‐deprivation therapy and experimental therapies in advanced prostate cancer are justified. Prostate 71:1455–1465, 2011. © 2011 Wiley‐Liss, Inc.