BOSTON (MarketWatch) -- Swiss conglomerate Roche said Friday that it has raised its offer for biotech giant Genentech Inc. to $93 a share from $86.50 a share. Genentech's board had deemed the previous offer as too low, asserting that the biotech group's value was closer to $112 a share. Roche already owns about 56% of Genentech's shares. Roche said its latest bid will expire at midnight Eastern time on March 20.