Patients with metastatic castration-resistant prostate cancer do not benefit from the addition of Reolysin (pelareorep) to Taxotere (docetaxel), according to recent data from a Phase 2 trial.
The trial (NCT01619813) failed to meet its primary endpoint of lack of disease progression at 12 weeks and secondary endpoint of overall survival, with patients receiving the combo treatment showing similar rates as those receiving Taxotere alone.
The findings, included in the abstract “A randomized phase II study of pelareorep (REO) plus docetaxel vs. docetaxel alone in patients with metastatic castration resistant prostate cancer (mCRPC): Canadian Cancer Trials Group study IND 209,” will be presented at the American Society of Clinical Oncology (ASCO) 2017 Annual Meeting in June.
“In recent years, we and our collaborators have performed numerous phase 1b and phase 2 trials to better understand the anti-tumour mechanisms of Reolysin, to identify the best therapies to pair with Reolysin, and to identify the cancer indications for which Reolysin provides clear benefit,” Dr. Matt Coffey, president and CEO of Oncolytics, said in a news release.
“While these results themselves indicate that prostate cancer is likely not a viable tumour target, they do not impact our focus on the advancement of Reolysin into a phase 3 registration study in patients with metastatic breast cancer,” he added. “We thank the investigators, staff and patients that participated in these trials that delivered very important data to guide the late stage development of Reolysin toward patient populations that can most benefit from its immune-oncology effects.”
Reolysin, developed by Oncolytics Biotech, is a proprietary formulation of the human reovirus that replicates specifically inside cancer cells, leading to their death. The virus also induces strong immune responses against the remaining cancer cells by releasing specific cancer proteins when cancer cells die.
The virus has shown some benefits against many cancer types, and has shown that it works in combination with drugs that target the microtubule cytoskeleton, such as Taxotere.
That led researchers to conduct the randomized, open-label, multicenter Phase 2 trial to evaluate Reolysin in patients receiving Taxotere. The study enrolled 85 mCRPC patients, randomized to receive Reolysin plus Taxotere, or Taxotere alone.
Its primary endpoint was disease progression at 12 weeks of treatment, and secondary endpoints included objective response rate, survival, and the number of tumor cells in circulation at specific timepoints. PSA and other prostate cancer biomarkers were also measured during the trial.
The newly revealed data shows that the trial failed to meet its primary endpoint, which was comparable in both study groups (61 percent vs. 52.4 percent).
Survival rates were worse in the combination group, compared to the group that received Taxotere alone. But the abstract reports significant differences among groups at baseline, with more patients in the combo group having poor prognostic factors for survival.
Dose reductions were also more common in those receiving both therapies, with only 51 percent of patients receiving 90 percent of the planned dose, compared to 76 percent in the control group.