The U.S. Supreme Court will not make a determination on Ranbaxy's challenge of the validity and enforceability of Pfizer's main Lipitor patent, the court said last week.

Ranbaxy took its case before the Supreme Court after the Federal U.S. Circuit Court of Appeals, a Washington, D.C.-based patent appeals court, denied the generic firm's request asking the court to rehear a decision it made last August upholding the exclusivity of the main Lipitor patent held by Pfizer. The case is Ranbaxy Laboratories Ltd. v. Pfizer Inc.

The ruling prevents Ranbaxy from launching generic atorvastatin, the active ingredient in Lipitor, before expiration of the main '893 patent in March 2010. The appeals court did, however, invalidate patent '995, a second patent challenged by Ranbaxy, which covers the crystalline form of atorvastatin. It was set to expire in June 2011.

Pfizer plans to request that the U.S. Patent and Trademark Office fix a technical defect in the second patent. The company expects to have the defect corrected within the next three years.

Ranbaxy had no comment on the Supreme Court decision.