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 small-cap biotech Halozyme Therapeutics (Nasdaq: HALO) plummeted 25% Monday after U.S. health regulators requested more information on HyQ, the immune-system disease drug it is developing with Baxter International (NYSE: BAX).

So what: The FDA request could delay HyQ's approval in the U.S. by a year or more, triggering fears that Halozyme will have to burn significantly more cash in 2012 than expected. Of course, the stock had been on fire over the past six months on positive data from a few of its other drugs, so today's big pullback isn't exactly the end of the world for Halozyme bulls.

Now what: Both Halozyme and Baxter will have to do more studies about HyQ's long-term use, and they expect to go before an FDA advisory panel that reviews blood products. "The companies expect these requests to require additional time to complete and to delay the companies' anticipated regulatory review and approval timeline," the two companies said. While Halozyme remains just too speculative for average investors, today's plunge might be a good opportunity for biotech-savvy investors intrigued by other parts of the portfolio.

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