The short interest data are out for the October 31 settlement date. Biotech companies are considered a riskier group of stocks, with big upside and big downside. FDA rulings can make or break them. A single failed clinical trial can mean disaster for a stock. 24/7 Wall St. has reviewed the top biotech companies, without focusing on speculative companies, such as Ebola-vaccine companies.

The October 31 short interest data has been compared with the October 15 figures, and biotech companies have received mixed readings, despite a few nearing 52-week highs in this period.

Amgen Inc. (NASDAQ: AMGN) saw its short interest fall to 10.8 million shares, with 1.61 days cover. The previous level was 11.2 million. Mid-September saw the 52-week high for short interest at 12.17 million shares. Despite this, the share price posted an annual high of $164.65 in late October. The stock closed Tuesday at $162.42, and it has a 52-week trading range of $108.20 to $164.65. One analyst said Amgen was a strong buy after its last earnings report.

Biogen Idec Inc.‘s (NASDAQ: BIIB) short interest dropped to 2.68 million, with 1.34 days to cover, from the 3.06 million shares short in the middle of October. Biogen is another company with short interest within a consistent range, specifically 2.0 million to 3.5 million. Shares closed Tuesday at $324.59, and they have a 52-week trading range of $232.11 to $358.89.

Celgene Corp. (NASDAQ: CELG) saw its short interest rise to 13.5 million shares, with 1.85 days to cover. The number of shares short was 11.8 million in mid-October. The short interest for Celgene can be split into two halves for the year: prior to April short interest held within a range of 4 million to 6 million shares, and since then the range has been 11 million to 15 million. Celgene announced a successful drug trial this quarter for its Crohn’s disease treatment, and the reaction in the market was very positive. Shares closed Tuesday at $107.85, within a 52-week trading range of $66.85 to $109.25.

Gilead Sciences Inc. (NASDAQ: GILD) short interest rose to 51.96 million shares, with 3.29 days to cover, from the previous level of 47.88 million shares. Despite the gain, this was still the third lowest number of shares shorted in the past 52-weeks, and it has been part of a declining trend in short interest since late July. Gilead has been pushing 52-week highs during this period, following the recent approval to sell its new hepatitis C drug. The stock closed Tuesday at $108.01 and has a 52-week range of $63.50 to $116.83.

MannKind Corp. (NASDAQ: MNKD) saw the number of its shares short increase to 82.03 million, with 16.10 days to cover, from the previous 78.22 million shares. The current level is the highest reading for the past 52 weeks, and this trend has been pushing higher, excluding a few drops, for basically the whole year. Investors still appear to be bearish on this stock and have latched on to its most recent slide from its 52-week high in June. MannKind shares closed Tuesday at $6.04, and it has a 52-week trading range of $3.80 to $11.48. Our latest take after earnings is that spending looks more controlled inside of MannKind now.

Alexion Pharmaceuticals Inc. (NASDAQ: ALXN) saw its short interest fall slightly to 3.21 million, with 2.25 days to cover, from 3.25 million in late September. Alexion has stayed consistent within the range of 3.0 million to 4.5 million shares short throughout the past 52-weeks. In this period, shares hit a 52-week high. The stock closed Tuesday at $194.92, within a 52-week trading range of $113.14 to $197.64.

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