Safety and Tolerability of PCK3145, a Synthetic Peptide Derived from Prostate Secretory Protein 94 (PSP94) in Metastatic Hormone-Refractory Prostate Cancer

Background

The safety, tolerability, and pharmacokinetic and preliminary efficacy of PCK3145 were determined in patients with metastatic hormone-refractory prostate cancer.

Patients and Methods

PCK3145 was administered in ascending doses of 5, 20, 40, and 80 mg/m² 3 times per week for 4 weeks to cohorts of 4 patients. Dose escalation was based on dose-limiting toxicity (DLT). Pharmacokinetic profiles, tumor burden, and tumor markers (including prostate-specific antigen [PSA] and matrix metalloproteinase-9 [MMP-9] levels) were assessed. Sixteen patients received PCK3145. The median age was 66 years, and the median PSA level was 232.5 μg/L. A total of 32 cycles of therapy were administered.

Results

The most common adverse events reported were pain and nausea. The only DLT was a grade 4 cardiac arrhythmia in a patient treated at the 80-mg/m² dose level. Pharmacokinetic analysis using a 2-compartment model indicated that the mean area under the curve values increased as the dose range increased, and the mean elimination half-life ranged from 0.35 hours to 1.45 hours. The best tumor response was stable disease in 10 patients and progressive disease in 5 patients. No PSA responses were observed, but 1 patient showed a marked reduction in PSA of 41% at cycle 2. A substantial reduction in MMP-9 levels was observed in patients with baseline levels of MMP-9 > 100 μg/L.

Conclusion

PCK3145 was safe and well tolerated at all doses. Efficacy observations were encouraging, and the biologic activity of PCK3145 in reducing MMP-9 level may suggest a potential role of this peptide in the regulation of metastatic tumor growth.