In the pharmaceutical industry, you can find stocks that double in value in one day. Onyx Pharmaceuticals (NASDAQ:ONXX) did so Monday after it reported positive results from a clinical study for cancer-fighting compound Nexavar.

Onyx and partner Bayer (NYSE:BAY) said they were prematurely halting a clinical trial testing Nexavar in advanced liver cancer, based on an interim review of the data. There were few details about the results because Onyx is waiting for the American Society of Clinical Oncology conference in June to announce the more complete data. What Onyx did tell investors was that Nexavar improved the chances for overall survival in patients taking the drug versus a placebo.

Even more importantly, the Food and Drug Administration had already said this primary endpoint was valid for the special protocol assessment, or special agreement, for this clinical trial. This in no way guarantees that the FDA will approve Nexavar to treat liver cancer. But combine this with the facts that Onyx said that the drug produced no differences in serious adverse events compared with the placebo and there are zero other approved treatments for this indication, and Nexavar is close to a lock for approval.

Onyx suffered a setback with Nexavar in November when there were disappointing results in trials for it as a treatment for advanced melanoma, but the drug is approved to treat advanced kidney cancer, where it competes primarily with Pfizer's (NYSE:PFE) Sutent. Sales of Nexavar -- Bayer records the revenues, then splits any profits with Onyx -- were $101 million through the first nine months of the year and are expected to reach $150 million for all of 2006.

The additional market for Nexavar to treat liver cancer is in the hundreds of millions of dollars, because no other drugs are approved for that cancer, which is the fifth-most common one in the U.S. with more than 19,000 new cases annually, according to the National Cancer Institute. Onyx gave no timelines but said an application to market the drug will be filed with the FDA and European Union authorities as soon as possible.

Nexavar is in various stages of clinical study for several different cancers. Despite the recent good news, and as the data in December and from other targeted therapies has shown, positive trial results for one type of cancer do not mean the drug will work for other types. This is something investors might want to consider when taking a closer look at Onyx.

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Fool contributor Brian Lawler has a great rock collection but does not own shares of Onyx or any other company mentioned in this article. Pfizer is an Inside Value recommendation. The Fool has a disclosure policy.