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for the years it would take to show a survival advantage for patients with slow-growing tumors like those of the prostate. It might take years to enroll all the patients, and since men with late-stage forms of prostate cancer have a life expectancy of 18 to 20 months, there would have been a lot of waiting. So the company came up with a primary goal that would provide a quicker answer. They looked at how long patients on the drug are able to keep their tumors from spreading-a goal that’s long been thought to be a reasonably accurate predictor of improved survival time.
That first trial, of 127 men, failed to show that Provenge could slow down the spread of tumors with the required statistical confidence. For many biostatisticians, that was the end of the story. The treatment had failed on its primary goal. Investors left the company for dead in 2002, driving the stock below $2. But Dendreon, again, in a desperate situation, fished around in the data for something positive to hang onto. For a while, it tried to convince investors there was a benefit for patients with slower-growing forms of tumors, just not for the most aggressive cases.
Many investors—and biotech industry peers—scoffed at this notion and figured the company was toast. But the story kept investors interested for a while, and it kept Dendreon in the game long enough so it could flip over an ace it had in the hole.
From the beginning of that trial, the FDA required the company to keep track of whether these patients were alive or dead for a full three years. It took time for this data to roll in, but the final analysis in 2005 showed that patients on Provenge ended up living a median time of 4.5 months longer than men who got a placebo. About one-third of the men on Provenge were alive after three years of follow-up, about triple the three-year survival rate of men in the control group. Side effects were minimal.
Dendreon hypothesized that the vaccine just took a while to kick in, a so-called “delayed effect” that might explain why tumors would spread shortly after treatment, but the treatment would end up helping patients live longer after all.
Patient advocacy groups cheered on Dendreon from the sidelines, saying they needed alternatives to the existing treatments-chemotherapy and chemical castration therapy-that have nasty side effects. Many scientists considered the Dendreon data intriguing, but the sort of thing that would need to be verified in another, larger trial.
While all of this was going on, Dendreon had another trial ongoing called Impact, and this time it had enrolled enough patients fast enough to produce a definite answer on survival. In consultation with the FDA, Dendreon agreed in November 2005 to expand the Impact trial to enroll 500 men with a broader range of tumor-aggressiveness scores, and make survival the main goal. After all of these meetings with the FDA to talk about next steps, and before the definitive results from Impact were ready, Dendreon decided to go for it anyway. It completed an application to the FDA in November 2006, asking it to approve the drug primarily on the basis of the survival benefit shown in the earlier study of 127 men.
This gambit was controversial. Many in the scientific and medical community wanted to see Dendreon hit the primary goal of a clinical trial designed to show it could help patients live longer. Many investors were skeptical that Dendreon could win approval on its thinner … Next Page »
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