Regeneron Pharmaceuticals (Nasdaq: REGN) looks like it shouldn't have much of a problem gaining expanded approval for its only drug, Arcalyst. Good thing, because the drug only managed to garner $25 million in sales last year. The new indication should easily make the company 10 to 20 times that.

Arcalyst is currently approved to treat Cryopyrin-Associated Periodic Syndromes, an ultra-orphan disease that only affects a handful of patients. Gout, the new indication that Regenron is testing Arcalyst in, is a considerably larger market.

The latest results confirmed earlier findings that Arcalyst is able to decrease painful flare-ups that gout patients often experience when they start taking allopurinol, an older medication for gout. The 72% decrease in mean number of gout flares compared with placebo is pretty significant.

While Arcalyst could theoretically be used by all gout patients starting therapy, doctors may wait to see if patients experience gout flare-ups before prescribing the drug that has to be injected weekly. In the placebo group, only 56% of patients had a flare-up during the 16-week trial.

The short time that the drug has to be taken -- compared to indefinite times for drugs like Pfizer's (NYSE: PFE) Lipitor, Merck's (NYSE: MRK) Januvia, and even Arcalyst for its original indication -- will make pricing the drug a little tricky. Still, anything will be better than what it's getting for CAPS alone.

Regeneron expects to file an application to sell the drug as a treatment for gout in the middle of the year. By the time it hears back from the agency, it could already have its second drug, VEGF Trap-Eye, on the market; the company submitted its marketing application for that drug to the FDA last week.

Despite the two major accomplishments, much of Regeneron's $3.2 billion market cap is tied up in its cancer drug, Aflibercept, which is partnered with sanofi-aventis (NYSE: SNY). Of the three, it probably has the biggest market potential. If the Aflibercept phase 3 trials don't come up positive, shares will sink.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.