A federal judge on Friday upheld the validity of two key U.S. patents on Pfizer Inc.'s Lipitor cholesterol drug, blocking a generic version of the medicine that threatened the company's largest source of revenue. The decision, which lifted Pfizer shares 10 percent, dealt a setback to Indian drug maker Ranbaxy Laboratories Ltd which had hoped to introduce the cheaper copycat as soon as 2008. Pfizer will now have patent protection on the world's best-selling drug through June 2011. Ranbaxy vowed to appeal the decision.

Lipitor is Pfizer's pillar of strength as the company's revenue growth and earnings continue to dwindle due to a raft of problems. Sales of Pfizer's Celebrex have been cut almost in half due to safety concerns. Revenue from Bextra was eliminated when the drug was withdrawn after being linked to a deadly skin condition.