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What: Shares of Rigel Pharmaceuticals (NASDAQ:RIGL) are trading about 9% higher this afternoon after topping out at a 15% gain in the morning following the company's publication of research results for R118.

So what: The results for studies with Rigel's R118, an orally bioavailable AMPK (AMP-activated protein kinase) activator, were published in the American Journal of Physiology today. Rigel's press release on the publication states that the studies indicate "strong preclinical evidence" that R118 might be used to treat peripheral artery disease (PAD), which afflicts roughly 5% of the over-50 population, and its related disorders. Rigel will now undertake phase 1 trials of R118 as a treatment for Intermittent Claudication, which is one of those "related disorders" tied to PAD.

Now what: Rigel was already on a strong momentum surge following its quarterly earnings report on Tuesday, and the company's stock is now up roughly 33% this week. This is the first bout of good news Rigel shareholders have enjoyed in over a year, as shares had been on a long decline since mid-2012 before finally bottoming out in December. Treating 5% of the over-50 population would be no mean windfall for Rigel, as it's estimated that at least 35% of the U.S. population will be 50 or older by 2020. Since the U.S. population is slated to increase to 341 million by 2020, Rigel would have roughly 6 million potential patients to treat. The question now is whether Rigel's treatment will work well enough to capture most of that treatment market or not.

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