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What: Myriad Genetics (Nasdaq: MYGN) shares dropped 11.5% in intraday trading today after some drug failures made the biotech company's financial health look pretty dim, at least for now.

So what: Myriad Genetics makes a test that shows whether a group of experimental new medicines can help patients with a difficult-to-treat form of breast cancer. Unfortunately for Myriad, sanofi-aventis' (NYSE: SNY) drug failed to show positive effect in a recent study, and AstraZeneca (NYSE: AZN) announced it won't go on testing its own similar drug.

Now what: Investing in biotech companies can be extremely risky, and Myriad Genetics' sad story today underlines that fact. Although other companies are trying to develop these drugs, these recent developments don't bode well for Myriad, since its test has no usefulness if the experimental drugs don't help breast cancer patients live longer. Taking a stake in Myriad now sounds awfully risky.

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Alyce Lomax does not own shares of any of the companies mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.