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 obesity-fighting biotech Arena Pharmaceuticals (NASDAQ:ARNA) shed as much as 11% today following its first-quarter earnings results and the company announcing the withdrawal of its European Union marketing application for Belviq.

So what: For the quarter, Arena Pharmaceuticals saw its loss narrow to just $0.09 from $0.18 in the year-ago period as revenue moved modestly higher to $2.37 million. Unfortunately, analysts had expected the Drug Enforcement Agency to have labeled Belviq by now and for Arena to have accepted a milestone payment from marketing partner Eisai Pharmaceuticals. Given that neither has happened, Arena's results were well short of the $68.3 million in revenue and $0.20 profit that the Street had expected.

Furthermore, Arena Pharmaceuticals pulled its application for marketing authorization in the EU in order to take its time to better understand what the EU's objections are to the drug. If you recall, VIVUS' Qsymia (known as Qsiva in Europe) failed to gain marketing approval in the EU last year due to long-term concerns about the drugs' effect on the heart and blood vessels.

Now what: Now we wait some more -- something Arena shareholders should be fairly good at by now. The DEA labeling will be a big boost as it'll clear the way for Belviq to make it onto pharmacy shelves and trigger a milestone payment from Eisai. Like VIVUS, I wouldn't expect sales to come roaring out of the gate, however, I do expect a sales ramp-up to occur more quickly than what we saw with VIVUS simply on the fact that Arena has a gigantic marketing partner in Eisai.

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

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