The addition of the experimental drug custirsen to docetaxel significantly extended OS in patients with metastatic castration-resistant prostate cancer who had negative prognostic factors, according to results of a phase 3 study.
The analysis included 984 men who were treated with docetaxel with or without custirsen (OGX-011, OncoGeneX) — a novel clusterin blocker — as first-line therapy.
After 509 patients had died, overall results from the SYNERGY trial indicated patients in the custirsen arm demonstrated similar median OS as patients in the control arm (23.4 months vs 22.2 months; HR = 0.93).
Kim N. Chi, MD, senior scientist at BC Cancer Agency, and colleagues hypothesized that clusterin inhibition may be more useful among a subgroup of patients with poor prognostic factors.
Thus, researchers retrospectively divided patients into good-risk and poor-risk groups using a prognostic statistical model based on commonly known risk factors in prostate cancer, including presence of liver metastasis, opioid use, Karnofsky performance status of 80 or lower, PSA of 59 ng/mL or higher, lactate dehydrogenase of 331 IU/L or higher, alkaline phosphatase of 92 U/L or higher, and hemoglobin less than 124 g/L.
That analysis included 492 patients with poor-prognosis disease. In that group, researchers reported longer median OS among those treated with docetaxel plus custirsen than those who received docetaxel alone (17 months vs. 14 months; HR = 0.73; 95% CI, 0.59-0.9).
Researchers then conducted an additional analysis of patients who had two or fewer negative prognostic factors. In this subgroup, median OS was 16 months among those who received custirsen and 13.7 months among those who received docetaxel alone (HR = 0.73; 95% CI, 0.58-0.92). – by Rob Volansky
Chi KN, et al. Abstract 5009.
Disclosure: The researchers report employment with OncoGeneX Pharmaceuticals, as well as stock ownership in and travel accommodations from OncoGeneX and Teva.