"Week-over-week prescriptions are increasing. We're very excited about that. And we expect those prescriptions to continue to increase as, yet a larger salesforce, goes into the field in the next few weeks."

-- Arena Pharmaceuticals (NASDAQ:ARNA) CEO Jack Lief on CNBC, June 11.

Lief was apparently so excited that he sold 38% of his stake in the company before the July 4 holiday. Investors are clearly not happy; Arena's shares fell last week, rebounded a little, but are still down substantially from where they were before the sale was announced.

Keep in mind that CEOs sell shares for all kinds of reasons. Earlier this year, Lief exercised options he had and sold the shares immediately for a profit of more than $180,000. Perhaps Lief plans to use the $1.3 million windfall from the current sale to buy a house. Property in San Diego isn't cheap you know.

Maybe he's just diversifying; he's ridden the Arena rollercoaster down and up and down again. Sometimes the front seat can be a little intense. And it's not like he got off the ride completely; he still owns almost $2 million worth of shares.

But if Lief thought there was a chance in the near future that Arena's shares were going to get to the highs the company saw in 2012 -- north of $11 per share -- it seems safe to assume that he wouldn't sell at $5.85. The inside knowledge of the day-to-day workings of the company says something about Arena Pharmaceuticals' short-term prospect.

Shares were sold under a 10b5-1 trading plan, so while Lief authorized the sale of the large block of shares, he didn't have any control over the exact timing of the sale. There's no reason to believe Lief thinks a large share price drop is imminent.

Neither is a large price increase
Arena Pharmaceuticals' marketing partner Eisai hasn't exactly rocked the launch that started in June 2013 with sales of just $8.4 million in the first quarter of this year. It doesn't seem like a problem with Qsymia per se since VIVUS (NASDAQ:VVUS) has equally struggled with its launch of Qsymia, registering just $9.1 million during the first quarter. We'll know for sure when Takeda launches Orexigen's (NASDAQ:OREX) Contrave later this year (assuming it gets approved).

Eisai increased its marketing muscle to 600 salespeople, but a lack of marketing isn't the real problem here. The only thing that's going to cure Arena, VIVUS, and Orexigen of their woes is time. Doctors have been burned too many times by side effects that have been revealed after obesity drugs have gone on the market, so they're rightfully a little apprehensive about prescribing the new drugs willy nilly. Over time, doctors will eventually become more comfortable with the drugs from Arena, VIVUS, and Orexigen and begin prescribing them to a wider audience.

If you're going to own the obesity drug makers, you should be taking a long-term perspective. There's clearly a large potential market, but it'll likely take years for them to reach it. And I'd suggest you follow Lief's lead and not take a large position in the companies. You can always add more when sales start to pick up.

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Brian Orelli and The Motley Fool have no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.

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