Pfizer Inc. said on Wednesday it was disappointed a federal appeals court had found that a secondary patent on its Lipitor cholesterol drug is invalid, but said it hoped to correct a "technical defect" in the patent.

The New York-based drugmaker said it hopes to correct the defect through a process at the U.S. Patent and Trademark Office. The patent is on a calcium salt form of the active ingredient of Lipitor, the world's biggest selling drug. It would have protected Lipitor from generic competitors until June 2011.

Earlier on Wednesday, the U.S. Court of Appeals for the Federal Circuit reversed a lower court decision which had accepted the validity of the patent. But the appeals court agreed with the lower court that another patent, covering the basic chemical structure of Lipitor, which extends to March 2010, is valid.