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 biopharmaceutical company MannKind (Nasdaq: MNKD) went on a roller-coaster ride today climbing slowly throughout the day before crashing 10% late in the day.

So what: MannKind is approaching a decision date for its inhaled insulin product, and investors are making bets on what the result will be. Option activity was up today and volume was nearly seven times average, and I expect more volatility through the end of the year.

Now what: If Afrezza is the drug MannKind thinks it can be, this stock will shoot higher to end the year, and investors who own the stock will make a killing on the stock. But the Food and Drug Administration has handed down some surprising defeats in recent months, and this isn't a slam-dunk case after Pfizer (NYSE: PFE) failed with high-profile inhaled insulin product Exubera. I've seen enough plunges in the drug business to keep me from making a bet here, but gutsy investors should make their bets before the 29th when the FDA's ruling is released.

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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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