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In a significant legal decision, the U.S. Supreme Court on Monday declined to hear Celanese International Corp.'s appeal regarding a patent dispute over the process used to create the artificial sweetener in Coke Zero. The case, which involves Celanese's challenge to a Federal Circuit ruling, addresses the patent eligibility of the process for producing acesulfame potassium, or Ace-K, a key ingredient in the popular beverage.

In an order list, the justices opted not to take up Celanese's appeal of the Federal Circuit's decision, which affirmed the ruling of the U.S. International Trade Commission (ITC) that invalidated Celanese's patent. The primary issue at hand was whether the "on-sale bar" — a rule that prohibits patents for technologies used or sold more than a year before a patent application is filed — applies to the Celanese process.

Celanese's patent claimed an improved method for producing Ace-K, but the process had been used in production for over a year prior to the patent filing. The company argued that the on-sale bar should not apply because the claimed invention, the Ace-K process, was not itself sold but was instead used to create an end product that was sold. They contended that under the 2011 America Invents Act (AIA), the on-sale provision only applies when the claimed invention itself is on sale, not when it is used to produce a product for sale.

The Federal Circuit, however, disagreed, ruling that the on-sale bar was triggered by Celanese's use of the process, and the Supreme Court declined to intervene.

The case also drew attention from industry groups, with the National Association of Manufacturers supporting Celanese's position. In an amicus brief, the group argued that the Federal Circuit's interpretation of the on-sale bar was inconsistent with international patent practices.

Celanese is represented by Deanne E. Maynard, Seth W. Lloyd, and Aaron G. Fountain of Morrison Foerster LLP. The ITC is represented by Wayne W. Herrington, Benjamin S. Richards, and Sarah M. Harris of the U.S. Department of Justice's Civil Division.

The case is Celanese International Corporation et al. v. International Trade Commission et al., case number 24-635, in the U.S. Supreme Court.