The 4th of July arrived a day early for investors in Dendreon

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[DNDN  Loading...      ()   ] . The stock is up, yet again, on heavy volume this morning after I reported on a new review published in the journal of the American Association of Cancer Research about therapeutic cancer vaccines (see video below). Dendreon's Provenge is a therapeutic vaccine. That means it's given after you get the disease to try to power your own immune system to combat it. It shouldn't be confused with traditional preventive vaccines which are given to hopefully keep you from coming down with something.

Researchers at the National Cancer Institute--part of the National Institutes of Health--looked at the results of five therapeutic prostate cancer vaccine clinical trials (including Provenge) and concluded that they appear to be extending patients' lives. Jeffrey Schlom, a Ph.D. who runs the NCI's Laboratory of Tumor Immunology and Biology, says "Clinical data are providing evidence that patients are living longer following vaccination, despite the fact that trials do not show the vaccines can induce the immune system into shrinking tumors. The data suggests that the scientific community and regulatory committees ought to rethink the design of clinical vaccine trials and our current approach to measuring the effectiveness of a cancer vaccine."

An FDA Advisory Committee recently recommended approval of Provenge. But the FDA delayed making a decision unless or until it sees positive survival data from an ongoing, large clinical trial. Dendreon says interim results won't be available until the middle of second half of next year. And final results won't be out for two to three yearrs from now. However, the company says the FDA may accept positive interim results for possible approval.

Some patients in earlier Provenge tests lived, on average, four-and-a-half months longer than those who got Sanofi-Aventis' Taxotere and hormone therapy. But detecting a survival benefit wasn't the goal of those studies, prompting critics to cast aspersions on the small size of the trials and the analysis.

The AACR, in a press release, says "According to the researchers, since they didn't achieve their primary endpoints (read: goals), these vaccines may be abandoned as dead-ends, despite their real therapeutic value in terms of prolonging patient survival. According to the researchers, it may be more helpful to think of the effectiveness of a vaccine in terms of the response of the patient, rather than the response of the tumor.

While there is no conclusive evidence to explain why a vaccine may lead to better patient survival, Schlom believes the evidence suggests that vaccines are, in fact, priming the immune system." And Schlom is quoted as saying, "Vaccines are not passive, they induce a dynamic process of immune response that, in many cases may keep the tumor in check and enhance the effectiveness of subsequent therapies."