Biomira: Study shows Stimulax may slow rising PSA levels in post-surgical cancer patients

By E. Janene Geiss

Philadelphia, July 20 - Biomira Inc. said Thursday that results of a phase 2 safety and efficacy study demonstrated that Stimulax, formerly known as BLP25 Liposome Vaccine, or L-BLP25, could slow rising Prostate Specific Antigen (PSA) levels in some post-surgical prostate cancer patients, potentially delaying the need for the start of androgen deprivation therapy.

PSA is a tumor marker used by physicians to detect prostate cancer, monitor treatment effects and guide medical management of men with this disease, rising levels being predictive of relapse and disease progression, according to a company news release.

The open-label 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 PSA levels post-surgery, final measurements having increased at least 50% above the lowest post-surgical level, officials said.

The primary endpoint was to determine if Stimuvax could stabilize or decrease serum PSA in these men. The secondary endpoints included safety and immune response measurements. Study treatment consisted of a primary and maintenance phase.

The primary treatment phase included a single dose of cyclophosphamide, used as an immunomodulator to enhance the potential activity of Stimuvax, followed three days later by the first of eight weekly vaccinations.

The maintenance phase followed, with the administration of vaccinations every six weeks for a maximum total of 15 doses over one year.

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, officials said.

These observations, along with favorable safety data, led to the conclusion that immunotherapy with Stimuvax may impart a positive effect on the population tested and warrants further testing in controlled studies in a larger patient population.

PSA doubling time is defined as the time it takes for the PSA value to double. This is used to help predict the possibility of metastasis and make treatment options.

The study results were described in an article entitled "A Pilot Study of the Liposomal MUC1 vaccine BLP25 in Prostate Specific Antigen Failures After Radical Prostatectomy" that appears in the July 2006 issue of the Journal of Urology.

Biomira is an Edmonton, Alta., biotechnology company.

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