Cell Genesys Rises on GVAX Trial Results

In a midstage trial, Cell Genesys said 34 of 80 patients showed an immune system response to the vaccine, and those patients lived for an average of 43 months. Those who did not have an immune system response lived for an average of 21 months.

The GVAX drug candidates are designed to fight cancer by boosting the immune system's response, and Cell Genesys said the results show the vaccine can stimulate effective responses to prostate cancer which is spreading.

Shares added 21 cents, or 10.8 percent, to $2.18 in afternoon trading on more than double average trading volume.

Twenty-two of the 65 patients for whom samples were available were given a high dose of the vaccine, and those patients who experienced an immune response lived an average of 44.9 months. The higher dose is being used in late-stage trials of the vaccine.

In an interview, Canaccord Adams analyst Joseph Pantginis said the trial shows the vaccine may increase survival more than older drugs do. The current standard of care in prostate cancer is Sanofi-Aventis' Taxotere, he said, and that drug increases survival by an average of 18 or 19 months.

In a client note, Pantginis said he thinks Cell Genesys will form a partnership later this year that will help it develop the GVAX vaccines. He named Bristol-Myers Squibb Co. and GlaxoSmithKline as potential partners.

The San Francisco-based company is also developing the vaccines as treatments for pancreatic cancer and leukemia.