We have tracked the key short interest changes in the following biotech and emerging pharma companies: Alexion Pharmaceuticals Inc. (NASDAQ: ALXN), Amgen Inc. (NASDAQ: AMGN), Arena Pharmaceuticals Inc. (NASDAQ: ARNA), Biogen Idec Inc. (NASDAQ: BIIB), Celgene Corp. (NASDAQ: CELG), Dendreon Corp. (NASDAQ: DNDN), Gilead Sciences Inc. (NASDAQ: GILD), Illumina Inc. (NASDAQ: ILMN), Onyx Pharmaceuticals Inc. (NASDAQ: ONXX), Pharmacyclics Inc. (NASDAQ: PCYC), Regeneron Pharmaceuticals Inc. (NASDAQ: REGN), Vertex Pharmaceuticals Inc. (NASDAQ: VRTX) and VIVUS Inc. (NASDAQ: VVUS). We also tracked the iShares Nasdaq Biotechnology (NASDAQ: IBB) against the group.
Alexion Pharmaceuticals Inc. (NASDAQ: ALXN) short interest fell 10.0% between July 31 and August 15 to 5.28 million shares, the smallest number of shares sold short since the mid May reading.
Amgen Inc. (NASDAQ: AMGN) short interest fell 5.8% to 11.85 million shares. The average daily volume was the lowest it has been this year.
Arena Pharmaceuticals Inc. (NASDAQ: ARNA) short interest rose 9.5% to 42.75 million shares. Days to cover has increased to 3.
Biogen Idec Inc. (NASDAQ: BIIB) short interest fell 8.4% to 2.24 million shares. The average daily volume was the lowest it has been this year.
Celgene Corp. (NASDAQ: CELG) short interest rose 1.5% to 6.40 million shares.
Dendreon Corp. (NASDAQ: DNDN) short interest rose 6.1% to 43.37 million shares. Short interest has been rising since the end of May, and days to cover is more than 8. Short interest is 28.8% of the float.
Gilead Sciences Inc. (NASDAQ: GILD) short interest rose 16.6% to 21.05 million shares, the greatest number of shares sold short so far this year.
Illumina Inc. (NASDAQ: ILMN) short interest rose 3.1% to 22.10 million shares. Days to cover is 25 and short interest is 18.3% of the float.
Onyx Pharmaceuticals Inc. (NASDAQ: ONXX) short interest fell 3.2% to 5.74 million shares. Short interest was 9.1% of the float.
Pharmacyclics Inc. (NASDAQ: PCYC) short interest rose 9.1% to 5.33 million shares. Days to cover rose from 5 at the July 31 reading to 7 by August 15. Short interest was 9.8% of the float.
Regeneron Pharmaceuticals Inc. (NASDAQ: REGN) short interest rose 0.1% to 4.97 million shares. Days to cover rose from 4 at the July 31 reading to 7.
Vertex Pharmaceuticals Inc. (NASDAQ: VRTX) short interest rose 21.8% to 6.39 million shares. After falling in the previous four periods, short interest has risen again.
VIVUS Inc. (NASDAQ: VVUS) short interest rose 18.5% to 16.44 million shares, the highest number of shares sold short since mid March. Short interest was 16.5% of the float.
To show how the sector has held up: the iShares Nasdaq Biotechnology (NASDAQ: IBB) ETF closed at $134.83 on the same date. Its current 52-week range is $87.67 to $138.75.
Trey Thoelcke