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 biopharmaceutical Orexigen Therapeutics (Nasdaq: OREX) more than doubled in early Wednesday trading after winning a Food and Drug Administration panel's backing for its new diet pill, Contrave.

So what: If approved, Contrave would be the first prescription weight-loss pill introduced in more than a decade, with peak sales being estimated at about $1 billion in 2016. The news comes as a particularly welcome surprise for Orexigen shareholders, given that competing treatments from Vivus (Nasdaq: VVUS) (Qnexa) and Arena Pharmaceuticals (Nasdaq: ARNA) (lorcaserin) -- whose shares are also up nicely on the news -- were previously rejected.

Now what: While this win for Orexigen eases some of the worries that have weighed on its shares in 2010, today's 100%-plus gain now has me concerned. With an estimated 68% of American adults being overweight, there's no denying Contrave's blockbuster potential. I'd just feel a lot more comfortable about jumping in when Mr. Market is a little less excited.

Interested in more info on Orexigen? Add it to your watchlist.

Fool contributor Brian Pacampara owns no position in any of the companies mentioned. Try any of our Foolish newsletter services free for 30 days.

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