The 12-year unfinished journey toward FDA approval for Dendreon's Provenge is not unique. It turns out that 12 years is the average length of time it takes for a drug candidate to progress from the lab to approval.

Getting out of the lab itself is a challenge. The industry estimates that just one out of every 1,000 molecules that make it to preclinical testing is deemed worthy of tests on humans. And only 20 percent of those tested on people get FDA approval.

Even though biotech companies often grow or are acquired by larger partners once they get a drug successfully to market, investors may not make any money. Only 30 percent of approved drugs generate enough revenue to match the capital investment that went into developing them.

Provenge isn't the first to hit major snags in the regulatory stage. Several other well-known drugs to burst out of Washington state's biotechnology labs followed that trend.

 Immunex Corp.'s Enbrel was developed relatively fast without major regulatory delays. But before Enbrel, the former Seattle biotech's flagship was Leukine, which boosts the immune system of patients with cancer and other conditions. It won approval in 1991, but in the mid-1990s, the FDA refused to approve its use as a chemotherapy drug, sending the company's stock down to less than $13 a share by spring 1995. By 1999, the company's stock crossed the $100-ashare level, thanks to Enbrel's success. In 2001, Immunex was acquired by Amgen.

 It took Icos Corp., the Bothell biotech acquired last year by Eli Lilly and Co., 10 years of work and testing before the FDA approved the erectile dysfunction drug Cialis in November 2003. The company had hoped for approval in 2002, but instead the FDA issued an "approvable letter," which is the agency's way of saying "Not yet." The stock had hit $70 in 2001 but later dropped to below $26 when FDA approval was delayed. When the company was sold, investors got $34 a share.

 Seattle's Corixa Corp. paid $900 million in 2000 to acquire a company that had developed Bexxar as a potential cancer drug. The FDA hadn't accepted the first application to review Bexxar for approval the previous year, and the second time around, the FDA said there weren't any clinical data on the drug. Then, in 2002, the FDA rejected Bexxar again. Corixa appealed, and an advisory panel recommended approval, which came in June 2003. Sales were slow, however, and Corixa sold Bexxar in 2004 to GlaxoSmithKline, which then bought the whole company the following year.

 ZymoGenetics of Seattle, founded in 1981, won approval in January of this year for Recothrom, a drug to stop excess bleeding during surgeries. The drug had taken just five years from the start of clinical trials to approval. But there were delays: The FDA delayed approval for three months last year to inspect a manufacturing facility in Italy where the drug is put into vials. Investors' celebration of the drug's approval didn't last long. The day after approval, ZymoGenetics' stock fell 16 percent, erasing $150 million in market value. Analysts and investors believed the drug's sales potential might not be as rosy as had been hoped. Since then, the company has laid off 80 people and Novo Nordisk, the Danish health care company that spun off Zymo- Genetics, has ended two drug development partnerships.