Last October at the European Cancer Congress 2013 there was a release of data from a phase 3 study of Ipilimumab (CA 184-043) that showed that it might be effective in treating castration-resistant prostate cancer in men who have a low burden of disease; however it failed to show at the required 95% confidence level required for FDA approval that it was a generally effective treatment for prostate cancer.

Ipilimumab (Ipi or Yervoy) is already approved and commonly used for the treatment of Melanoma. Ipi is an immune therapy that differs in its mode of action from the already approved immunologic therapy Provenge (approved for the treatment of prostate cancer). Provenge sensitizes the immune system to fight prostate cancer by training the immune system to recognize cancer cells while Ipi removes the breaks on the immune system allowing it to generally attack the cancer.

The reported data was derived from the CA 184-043 trial, a Phase 3, multicenter, randomized, double blind trial of 799 men with castration-resistant prostate cancer treated with ipilimumab or placebo after docetaxel and a single radiation dose (8 Gy).  The subject men had to have one or more symptomatic bone metastases that could be irradiated with a single dose of radiotherapy (8 Gy).

After the irradiation, 399 of the men were randomized to receive ipilimumab at an intravenously infused dose of 10 m