Here are the biggest percentage gainers and losers in pre-market trading among companies with a market cap between $50 million and $750 million:

Biggest percentage gainers:

• Sirtris Pharmaceuticals Inc.(Nasdaq:SIRT), up 82% on news that it will be acquired by GlaxoSmithKline for $720 million.

• Green Bankshares, Inc. (Nasdaq:GRNB), up 14% on news that the bank reported first-quarter results that substantially beat the Street.

• China Finance Online Co. Ltd. (Nasdaq:JRJC), up 2%.

Biggest percentage losers:

• Wavecom S.A. (Nasdaq:WVCM) down 17%, on news that it swung to a net loss in the first quarter, while revenue declined 21%.

• Innovative Solutions & Support Inc. (Nasdaq:ISSC), down 14% on disappointing second-quarter results that clocked in below the Street.

• WebMD Health Corp. (Nasdaq:WBMD), down 8%, on lowered guidance for 2008.