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 Pharmacyclics (Nasdaq: PCYC), a biotech specializing in small-molecule treatments for cancer and immune diseases, fell nearly 13% on more than double its average daily volume before closing down around 5%.

So what: Far as I can tell, no news precipitated the drop. So be it. Volatile biotechs are notoriously susceptible to broad market fears, and with Mr. Market howling at the rain as he has, some issues were bound to take a beating. Pharmacyclics just had its day.

Now what: Whether the selloff represents a buying opportunity is a matter of debate, but with insiders buying up shares recently, executives have a lot riding on a recovery. Betting alongside them might not be a bad idea. Do you agree? Disagree? Weigh in using the comments box below.

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