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: Lexicon Pharmaceuticals (Nasdaq: LXRX) shares fell as much as 14% in intraday trading on disappointing results of its rheumatoid arthritis drug test.

So what: The drug, LX2931, showed a positive response in high doses, but low doses showed a response rate lower than a placebo. The company said it was happy with the safety profile and is planning to start discussions with potential partners.

Now what: Lexicon is counting on LX2931 to perform better than we have seen, and despite the company moving forward, I am concerned with today's results. After knocking shares down early, the stock has come back steadily throughout the day, indicating that investors are still willing to bet on the company. Still, I don't see today as a buying opportunity and will stay away until I see some positive results from Lexicon.

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Fool contributor Travis Hoium does not have a position in any company mentioned. You can follow Travis on Twitter at @FlushDrawFool, check out his personal stock holdings or follow his CAPS picks at TMFFlushDraw.

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