REO 002 was an open-label, single arm study of REOLYSIN® monotherapy in patients with T2 prostate cancer. A total of six patients were enrolled. Each received a single injection of REOLYSIN® and were monitored for approximately three weeks, at which time the prostate was surgically removed. The primary objectives of the study were to determine the safety of the treatment and the response rate as measured by pathological examination of resected tumour tissue.
The Company announced interim results from the study in March 2003. There was evidence of viral activity in five of the six patients, and there were no safety concerns, from either a clinical or histopathological perspective, in all six patients. The preliminary data showed clear histopathological evidence of apoptotic tumour cell death, one measure of viral activity, in four of the six patients. In a fifth patient, the PSA level dropped by 53% and the prostate gland shrank by 67% from just prior to treatment to the time of surgical removal. There was no evidence of viral activity in the sixth patient. In all six patients, there was no histopathological evidence of any viral effect on healthy prostatic tissue. Additional histopathological analysis has demonstrated immune cell infiltration (B and T cells) into virus infected tumour mass. This infiltration was not noted in adjacent normal tissue. Further histopathological analysis including microarray (a measure of gene expression) is currently being conducted. Information obtained in these studies is intended to be utilized in future systemic studies to assess optimal dosing and response.
Final results from the study were released in February 2004. It was noted that the trial had met its histopathological objective of showing that REOLYSIN® infected and selectively killed tumour cells in humans without damaging adjacent healthy tissue. Final results showed evidence of apoptotic tumour cell death in four of six patients, with no safety concerns. A fifth patient saw prostate-specific antigen (PSA) levels drop by 53% and prostate shrinkage of 67% during the three week period from just prior to treatment until surgical removal.