In Takeda Pharmaceutical Co. v. Zydus Pharmaceuticals USA, Inc., Appeal No. 13-1406, the Federal Circuit reversed a district court’s finding of infringement and affirmed its judgment of claim validity.

Takeda sued ANDA-filer Zydus for infringing a formulation patent relating to an acid reflux drug. Claim 1 of the patent recites a formulation with “fine granules having an average particle diameter of 400 µm or less.” The district court construed that term to include particle diameters within the accepted margin of error of ±10%. Based on this claim construction, the district court determined that Zydus’s product infringed Takeda’s patent. The district court also determined that Zydus failed to prove that the claim was invalid for failure to comply with the definiteness, written description, and enablement requirements. Zydus appealed.

The Federal Circuit reversed the district court’s infringement finding and instead concluded that the proper construction of the disputed claim term is “fine granules having an average particle diameter of precisely 400µm or less.” The Federal Circuit based its construction on the fact that the specification discloses that the maximum particle size is “practically 425 µm or less.” The specification’s use of the word “about” at three points in the specification did not justify a 10% expansion of claim scope. The Federal Circuit then upheld the district court’s finding of validity. Zydus had argued that the claim is indefinite because it does not specify the measurement method used to determine average particle diameter. In rejecting that argument, the Federal Circuit held that “the mere possibility of different results from different measurement techniques” does not render the claim indefinite. Regarding enablement, the Federal Circuit held that, because the patent identifies one viable measurement technique, there is no dispute that a skilled artisan would know how to use that technique to measure particle diameter.