Phase II Trial of Copper Depletion with Tetrathiomolybdate as an Antiangiogenesis Strategy in Patients with Hormone-Refractory Prostate Cancer

Abstract

Objective: Preclinical studies suggest antiangiogenesis strategies may be effective in the treatment of prostate cancer. In tumor models, the copper-chelating agent tetrathiomolybdate (TM) has been shown to be antiangiogenic. We evaluated the antitumor activity of TM in patients with hormone-refractory prostate cancer (HRPC). Methods: Nineteen patients with asymptomatic HRPC enrolled. Copper depletion was monitored using serum ceruloplasmin levels. Once the target ceruloplasmin level of 5–15 mg/dl was attained, patients underwent staging evaluation. Patients were reassessed every 12 weeks, and TM was continued until they developed evidence of disease progression or intolerable toxicity. Prostate-specific antigen and levels of vascular endothelial growth factor, basic fibroblast growth factor, interleukin (IL)-6 and IL-8 were measured at study entry, at the time of copper depletion, and monthly while on therapy. Results: Seventeen of 19 patients achieved copper deficiency on TM therapy. Of the 16 evaluable patients, 14 developed progressive disease, 1 discontinued therapy because of toxicity and 1 patient opted to discontinue therapy because of rising prostate-specific antigen level without objective evidence of progressive disease. Levels of vascular endothelial growth factor, IL-6 and IL-8, but not basic fibroblast growth factor, were elevated when compared to normal controls prior to TM therapy, but there was no significant change during therapy. There was no correlation between prostate-specific antigen and levels of angiogenesis factors. Conclusions: Copper depletion with TM did not delay disease progression in patients with asymptomatic metastatic HRPC.