Shares of Otonomy Inc. (OTIC) rose 9.1% to $3.90 in premarket trading on Thursday, Aug. 31, after plunging on Wednesday on the heels of word that the San Diego firm's Phase 3 study of Otividex in patients with Meniere's disease missed its primary endpoint.

The stock ended Wednesday at $3.58, down 82.8%.

Meanwhile, shares of Merrimack Pharmaceuticals (MACK) were down 9.1% to $1.20. The Cambridge, Mass.-based firm said Thursday that its previously disclosed one-for-ten reverse stock split will take effect as of the start of trading on Sept. 6.

The company said the reverse stock split will decrease the number of shares of common stock outstanding from about 132.8 million shares to about 13.28 million shares. In addition, it will proportionately lower the number of authorized shares of common stock from 200 million to 20 million.

"We appreciate the support of our stockholders in taking this action, which is designed to benefit our equity structure and broaden the investor appeal of our stock," said Merrimack president and CEO Richard Peters in a statement. "We are well-positioned for a catalyst-rich 2018, with data expected for each of our three lead product candidates and a strong financial profile which we believe will fund operations into the second half of 2019."

Among the other biotech movers was Rigel Pharmaceuticals Inc. (RIGL) , up 6.5% to $2.62.

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