Prostate cancer vaccine teams up with antibody

Sometimes, the sum of the parts is greater than the whole, and this can be true for cancer therapies as well. Researchers are hoping that combining Prostvac, the investigational therapeutic cancer vaccine, with ipilimumab, a monoclonal antibody, will enhance treatment effects. And results from an early clinical trial hint it just might work.

The study looked at Prostvac, Bavarian Nordic's poxvirus-based investigational therapeutic cancer vaccine, and Bristol-Myers Squibb's ($BMY) Yervoy (ipilimumab) in men with metastatic castration-resistant prostate cancer. Yervoy is approved for the treatment of melanoma.

In the study, 30 men received increasing doses of ipilimumab and fixed doses of Prostvac. There were no side effects that limited the amount of drug the men could receive. The side effects were those expected with ipilimumab, and the vaccine didn't seem to make them worse. Half of the patients saw decreases in prostate-specific antigen, a biomarker of prostate cancer, some by more than 50%, and the median overall survival was around three years.

According to James Gulley, director of the Clinical Trials Group at the Laboratory of Tumor Immunology and Biology at the National Cancer Institute, although the Phase I trial was small and non-randomized, the median overall survival of 34.4 months for the 30 patients treated raises the possibility the ipilimumab/Prostvac combination might result in prolonged overall survival.

Phase I trials are designed to prove concepts and check out the safety, and that this has shown some effects on biomarkers--and perhaps even on survival--has given the researchers hope it could help prostate cancer patients, but only further clinical trials designed to look at efficacy will tell. Prostvac started Phase III trials in November 2011.

- read the press release
- see the abstract in The Lancet Oncology