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 Aegerion Pharmaceuticals (NASDAQ:AEGR), a biopharmaceutical company focused on developing drugs to treat rare diseases, plunged as much as 31% after reporting disappointing first-quarter results after the closing bell last night.

So what: For the quarter, Aegerion reported $27 million in total sales of Juxtapid, its oral therapy to treat homozygous familial hypercholesterolemia. This figure represents 24% sequential quarterly growth, with 96% of all sales coming from within the U.S. Net loss for the quarter shrank by 50% to $7.3 million or $0.25 per share. But compared to Wall Street's estimates, today was entirely a top-line problem because Wall Street had been expecting Aegerion to record $33.6 million in revenue for the quarter. The company blamed longer turnaround times on price quotes and orders in Brazil, as well as an ongoing investigation into possible violations of anticorruption laws in connection with sales of the drug in Brazil, as a reason ex-U.S. prescriptions dipped 70%.

Given these external pressures Aegerion lowered its full-year sales forecast to $180 million-$200 million from a prior forecast of $190 million-$210 million and forecast reaching positive cash flow status by the second-half of this year.

Now what: Even down nearly 70% from its 52-week high and I still can't say I'm a fan of Aegerion Pharmaceuticals. I still fail to see how it can price its HoFH therapy more than $100,000 over the price of Kynamro, a competing therapy, and expect to thrive. As we're seeing today, drug development is really only half the battle nowadays for biopharmaceutical companies. They also need to be able to properly execute a drug launch and become profitable. At the moment Aegerion is still losing money and it's got a lot of kinks to apparently work through in overseas markets. I know its forward P/E might look appealing, but I'd suggest sticking to the sidelines until we see demonstrable progress from Aegerion in reducing its quarterly losses.

Juxtapid may have world's of potential, but even Aegerion may struggle to keep pace with this top stock over the long run
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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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