Prostvac

Vaccine: Prostvac
Company: Bavarian Nordic
Target: Castration-resistant prostate cancer

Sometimes two are better than one, especially where advanced cancer is concerned. A Phase I study that combined Prostvac, Bavarian Nordic's poxvirus-based investigational therapeutic cancer vaccine, with Bristol-Myers Squibb's ($BMY) Yervoy (ipilimumab) in men with metastatic castration-resistant prostate cancer showed that the combination may enhance the clinical efficacy of the two drugs. Yervoy is already approved for the treatment of melanoma, and Prostvac is in a global Phase III trial, known as PROSPECT, which began in November 2011.

In the study, men received increasing doses of ipilimumab and fixed doses of Prostvac. This was a small and non-randomized study, but even so, the combination produced a median overall survival of 34.4 months, an 8.5-month improvement, along with decreases in levels of prostate-specific antigen (PSA), a prostate cancer biomarker. Some of these reductions were more than 50%.

The results are intriguing and could hint toward the efficacy of combined therapies--a study under way with the Cancer Institute of New Jersey (CINJ) and the National Cancer Institute is looking at combining Prostvac with flutamide, a standard hormone therapy for prostate cancer, to see if adding the two together will help in hormone-resistant cancer.

In another combination approach, adding Prostvac to a radiopharmaceutical, Quadramet (samarium-153 EDTMP) in patients with metastatic castration-resistant prostate cancer, was well-tolerated, with early signs of an increase in the time to tumor progression.