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 biopharma company Cytokinetics (Nasdaq: CYTK) dove more than 20% on heavy volume after the company announced Phase 2a results on its amyotropic lateral sclerosis (a.k.a. Lou Gehrig's disease) drug.

So what: Rather than a treatment for the disease, the drug is a therapy that's hoped could improve the quality of life for ALS sufferers. During the trial, six hours after receiving a 500-milligram dose of the drug, 29 of 65 patients reported feeling better versus 18 of 63 on a placebo. Additionally, 20 of the 65 patients on the 500-mg dose were evaluated as better versus eight of 63 on the placebo. The patients' self-reported results were considered close to statistically significant, while the results from the evaluation by the investigators were deemed statistically significant. Though the outcome of the study seems promising, it apparently wasn't enough of a slam dunk for investors as they sold the stock in droves today.

Now what: While there is still plenty left for Cytokinetics to do before this drug could hit the market, investors are trying to get ahead of the game and estimate what these trial results could mean for the future. Specifically, they are likely considering not only how probable it is that the drug ultimately gets approved, but also how much testing will be required before an approval; more testing means more spending, and it also delays the eventual payoff. In the meantime, there aren't many promises when it comes to drug development, but it seems like volatile stocks are something that investors can almost always count on.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy assures you no Wookiees were harmed in the making of this article.