Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Ligand Pharmaceuticals (NASDAQ:LGND), which acquires and develops drugs for royalty revenue purposes, rose as much as 19% following the Food and Drug Administration's approval of a rival's hot-flash drug in the U.S.

So what: I'm certain that has to sound a bit confusing that Ligand jumped based on Hisamitsu Pharmaceuticals getting its drug (to be called Brisdelle) approved for the treatment of hot flashes associated with menopause -- but there is a perfectly reasonable explanation. The FDA has previously come down very stringently on hot-flash drugs in the U.S., and this marks the first non-hormonal drug to be approved. This is important because Pfizer (NYSE:PFE) and Ligand Pharmaceuticals have a similar drug, bazedoxifene, which, when combined with conjugated estrogens, is aimed at treating hot flashes, vulvar and vaginal atrophy associated with menopause, and the prevention of osteoporosis associated with menopause. The FDA is expected to make its decision on bazedoxifene in October.

Now what: I think it's probably a bit premature for Ligand shareholders to get too excited, especially given the FDA's harsh stance on non-hormonal hot-flash treatments previously. Also, peak sales estimates of the drug are all over the place. Understandably, there's no shortage of prospective patients, but getting the drug to market, pricing it properly, and launching it effectively are all question marks that can't even be answered until October. As for now, I'd suggest letting calmer heads prevail and sticking to the sidelines.

Craving more input? Start by adding Ligand Pharmaceuticals to your free and personalized watchlist so you can keep up on the latest news with the company.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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