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 MannKind (NASDAQ: MNKD), a biopharmaceutical company with a focus on novel therapies to treat diabetes and cancer, soared as much as 36% after the company reported positive late-stage trial results for afrezza.

So what: According to MannKind's press release before the opening bell, its experimental inhaled insulin drug, afrezza, met its primary endpoint in both the type 1 diabetes and type 2 diabetes trials. With regard to type 1 diabetes, afrezza was shown to be non-inferior to the oral placebo in decreasing A1C levels, while resulting in fewer cases of hypoglycemia and demonstrating weight neutrality (some marketed type 1 diabetes medications can cause weight gain). In its type 2 diabetes trial, afrezza demonstrated "superior reductions" in A1C levels with no significant difference in hypoglycemia incidence relative to the placebo. MannKind now expects to submit a new drug application to the Food and Drug Administration by the fourth quarter.

Now what: Afrezza meeting its primary endpoint in both trials certainly has to be a big weight off of shareholders' shoulders, but it doesn't put the company completely out of the woods just yet. The FDA has been known to be hypercritical about the quality and manufacturing aspects of inhaled device technology, and actually sent MannKind back to the drawing board in early 2011 with a complete response letter for afrezza when questions were raised by the agency over the effectiveness of the drug and its inhaler. The other concern here is whether MannKind seeks out a marketing partner or attempts to market afrezza itself. Ultimately, it will see beefier returns on its investment if it goes it alone, but with little marketing experience selling (and pricing) drugs, it runs the risk of encountering serious launch issues. With the FDA having proven very unpredictable in the past, I would still suggest staying on the sidelines until after afrezza's PDUFA date, which should be sometime around mid-2014.

Biotech stocks like MannKind can certainly provide a nice pop to investors because of clinical study data from time to time, but the best investment strategy is to pick great companies and stick with them for the long term. The Motley Fool's free report, "3 Stocks That Will Help You Retire Rich," not only shares stocks that could help you build long-term wealth, but also winning strategies that every investor should know. Click here to grab your free copy today.

Fool contributor Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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