(ChemotherapyAdvisor) – A higher number of chemotherapy-naïve patients with metastatic castration-resistant prostate cancer were progression-free at 12 weeks when treated with OGX-427 plus prednisone vs. prednisone alone, preliminary results from a Phase 2 study in reported at the 2012 Genitourinary Cancers Symposium have shown.
“The PSA declines, progression-free survival at 12 weeks, and response rates observed thus far are supportive of OGX-427’s ability to suppress androgen receptor activity and tumor cell survival through inhibition of Hsp27,” said Kim N. Chi, MD, British Columbia Cancer Agency, Vancouver, BC, Canada.
To date, the study has randomized 17 patients to OXG-427 600mg IV x 3 loading doses followed by 1000mg IV weekly plus oral prednisone 5mg twice daily and 15 to prednisone at the same dosage. Enrollment of an additional 32 patients is planned to provide statistical power to detect a difference between the two arms.
At 12 weeks, 71% of patients were progression-free in the OGX-427 plus prednisone arm vs. 33% in the prednisone alone arm. An overall decline in PSA was experienced by 76% vs 53% of patients, respectively; 41% vs 20% experienced a >50% decline in PSA. Among 17 patients with baseline measurable disease, 8 (38%) in the OGX-427 plus prednisone arm had a partial response vs. none (0%) in the control arm. Circulating tumor cells declined from ≥5 to <5 in 50% of patients receiving OGX-427 plus prednisone vs. 31% of those treated with prednisone alone.
Grade 3 or higher adverse events (AEs) were observed in 31% of patients in the OGX-427 plus prednisone arm and in 25% in the control arm. OGX-427 infusion reactions were primarily grade 1 or 2 chills, nausea, vomiting, flushing or diarrhea. Other AEs believe to be related to OGX-427 were fatigue, dizziness, decreased appetite, and pyrexia.
OncoGenex Pharmaceuticals, Inc., which is developing OBX-427, is initiating a Phase 2 study of OGX-427 in combination with abiraterone in castrate-resistant prostate cancer.
The 2012 Genitourinary Cancers Symposium is sponsored by the American Society of Clinical Oncology, American Society for Radiation Oncology, and the Society of Urologic Oncology.