While several biotech stocks sold off today in a broader industry sell-off, two stocks in this sector fell today because of their own bad news. Geron (NASDAQ:GERN) tumbled by about 15% today, after The Mayo Clinic announced that the trial for Geron's cancer drug Imetelstat for the myelofibrosis indication is closed, though no efficacy data was released. More than 25% of the patients in the trial have now dropped out, which has investors in Geron spooked.

Pfizer (NYSE:PFE) also lost today, as the company's lung cancer drug Dacomitinib failed two phase 3 trials. The drug was unable to prolong overall survival rate over the placebo or progression-free survival against Tarceva.

In this video, Motley Fool health-care analyst David Williamson gives investors his thoughts on Geron and Pfizer today.

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David Williamson owns shares of Pfizer. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't 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.