Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc.

Teva's (plaintiff) patent described its multiple sclerosis drug's active ingredient by a specific molecular weight range, and Sandoz (defendant) argued the patent was invalid as indefinite because three different methods could calculate that value; after hearing competing expert testimony, the district court found a skilled artisan would understand the patent to specify the peak average calculation method, upholding validity, but the Federal Circuit reviewed all determinations de novo and reversed, finding the term indefinite.