GlaxoSmithKline said today that it has extended by two days its offer to buy all outstanding common shares of California-based Genelabs Technologies Inc. ( for $1.30 a share.

London-based Glaxo, which has a major presence in Philadelphia, originally made its offer to expire at midnight Wednesday.

As of 5 p.m. (Philadelphia time) Dec. 5, about 7.8 percent (or 3.46 million) shares of Genelabs common stock had ben tendered. Glaxo's offer had called for 90 percent of the shares to the tendered.

Glaxo had said earlier that the deal would strengthen its effort to develop treatments for the hepatitis C virus, one of six identified hepatitis viruses, which causes the liver to become inflamed.

Glaxo shares were trading this morning at $36.54, up 73 cents (2.04 percent) on the New York Stock Exchange. Shares of Genelabs were prices at $1.29, up 1 cent, in Nasdaq trading.