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 Keryx Biopharmaceuticals (NASDAQ:KERX), a biopharmaceutical company focused on developing products to treat renal disease, fell as much as 15% after reporting weaker-than-expected first-quarter results.

So what: For the quarter, Keryx reported licensing revenue of $10 million from JT/Torii, the company's marketing partner for Zerenex, a treatment for hyperphosphatemia in patients with chronic kidney disease on dialysis, in Japan. This compares favorably with the $7 million in licensing revenue recorded in the year-ago quarter. Net loss for the quarter widened to $13.5 million, or $0.15 per share, from just $2.1 million, or $0.03 in Q1 2013. Higher expenses tied to its expected launch of Zerenex were the main reason losses widened. Comparatively, Wall Street anticipated a much narrower loss of just $0.08 per share. Also, per Keryx's press release, it ended the quarter with $155.1 million in cash, cash equivalents, and short-term investments following a $107.6 million cash raise in the first quarter.

Now what: Simply put, we're getting close to crunch time for Keryx with its PDUFA decision date on Zerenex right around the corner (June 7), and investors are a little skittish, to say the least. Despite strong clinical results there's no such thing as a guaranteed approval when it comes to the FDA, and Keryx's recent dilutive offerings to raise cash for the Zerenex launch combined with its higher operating costs pushed the company's loss well beyond what investors had expected. As we've seen in recent years, getting a drug approved is only half the battle. Being able to effectively market that drug and turn a profit is an entirely different uphill battle. Considering that Keryx shares have already had a monstrous run higher, I'd be perfectly content sticking to the sidelines until well after its PDUFA date and, if approved, even waiting out a few initial quarters of sales to get a bead on its initial acceptance.

Keryx shares have soared over the past year, but even it could have a tough time keeping 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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