An open-label phase II safety and efficacy trial enrolled 16 post-radical prostatectomy patients. Patients enrolled in the trial had undergone this surgery at least six months prior to study entry, but experienced rising prostate specific antigen (PSA) levels post-surgery, final measurements having increased at least 50% above the lowest post-surgical level.
The primary study endpoint was to determine if Stimuvax could stabilize or decrease serum PSA in these men. Secondary endpoints included safety and immune response measurements.
While no decreases in PSA occurred during the study period, PSA stabilization occurred in 50% of patients at the end of the primary treatment phase, and was maintained in one patient at the end of the study. Another interesting outcome was a noted increase in the PSA doubling time, which was prolonged by more than 50% in six men at the end of the trial, compared with the doubling time prior to vaccine treatment.
These observations, along with favorable safety data, led the study’s authors to conclude that immunotherapy with Stimuvax may “impart a positive effect on the population tested,” warranting further testing in controlled studies in a larger patient population.
“While we are not currently pursuing a prostate cancer application for Stimuvax, these clinical trial results…support the potential value of cancer vaccine approaches to patients with few therapeutic options and our future plans for this product candidate, which include an upcoming phase III study in non-small cell lung cancer,” said Biomira’s interim president and CEO Edward Taylor.