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 biotechnology company Incyte (NASDAQ:INCY) lost as much as 13% following the disclosure in a regulatory filing that a patient had developed a case of progressive multifocal leukoencephalopathy, or PML, while taking its lead drug, Jakafi.

So what: Jakafi, which is designed to treat patients with myelofibrosis, is marketed outside of the U.S. as Jakavi by licensing partner Novartis (NYSE:NVS). According to the filing, Incyte has alerted the Food and Drug Administration to this case and is in the process of informing investigators currently in clinical trials. However, the company was also clear to point out that people with myelofibrosis could be at higher risk of developing PML to begin with, and it hasn't been determined whether Jakavi was a direct cause of this particular patient developing PML.

Now what: While I'd hardly call this finding good news, I think investors have probably overreacted to an as of now unproven case of PML as compared to the nearly 10,000 prescriptions written around the globe for Jakafi/Jakavi without any serious adverse events. Myelofibrosis patients have few treatment alternatives and Jakafi was proven to be effective in trials, so I highly doubt major corrective action is in order. Investors could be getting quite the bargain picking up Incyte shares on dips related to this news.

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