The 10 biotech and drug stocks with the largest short interest as percentage of float, according to S&P CapitalIQ:

10. Spectrum Pharmaceuticals (SPPI) (26.8% shares short)

^NBI Chart
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9. Dendreon (DNDN) (29.6% shares short)

DNDN Chart
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8. Achillion Pharma (ACHN) (29.7% shares short)

^NBI Chart
^NBI data by YCharts

7. Arena Pharmaceuticals (ARNA - Get Report) (29.9% shares short)

ARNA Chart
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6. Ziopharm (ZIOP) (30.9% shares short)

ZIOP Chart
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5. Intrexon (XON - Get Report) (32.8% shares short)

XON Chart
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4. Idenix Pharma (IDIX) (33.3% shares short)

IDIX Chart
IDIX data by YCharts

3. Synta Pharma (SNTA) (36.4% shares short)

SNTA Chart
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2. Sarepta Therapeutics (SRPT - Get Report) (39% shares short)

SRPT Chart
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1. Myriad Genetics (MYGN - Get Report) (52.4% shares short)

MYGN Chart
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Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.