Aventis Pharma S.A. v. Amphastar Pharmaceuticals, Inc. 525 F.3d 1334 (Fed. Cir. 2008) Aventis invented a drug to stop blood clots. They filed for a patent on the drug. It was initially denied. The USPTO found that the drug was obvious when compared to some prior art. If Aventis wanted a patent, they would have to show how their drug had different properties than what was already available in the prior art. Aventis came back and amended their patent. This time it was approved. Avantis amended their patent to show evidence that their drug stayed in the body for less time (aka had a shorter half-life) than the drugs described in the prior art. That made it different. In the biochemical community, it is often difficult to tell exactly what a compound is, so patents are granted more on what the properties of the compound is, not what the exact compound is. Amphastar was marketing their own, similar blood clotting drug. They sued Aventis to have the Aventis patent invalidated. Amphastar argued that when Aventis did their half-life tests, they used a different dosage for their drug than for the drugs in the prior art. That's why the half-lives appeared to be different. Amphastar argued that this was deceitful and so Aventis' patent should be invalidated due to inequitable conduct. The Trial Court invalidated the patent. Aventis appealed. The Trial Court found that Aventis was guilty of inequitable conduct. The Court found that there was evidence of an intent to deceive because there was no scientifically defensible reason why Aventis should have used different dosages, and no legitimate reason for their failure to disclose that fact to the USPTO. Note that if you are found guilty of inequitable conduct on even a single small point then the entire patent is declared invalid. You can't amend, or just throw out the single claim. See 35 U.S.C. §251. The Appellate Court affirmed. The Appellate Court found that there are two elements to inequitable conduct - an intent to deceive, and the materiality of the deception. The Court found that the more material the omission or misrepresentation, the less intent must be shown to elicit a finding of inequitable conduct. The Court looked at the evidence, and found that there was a lot of evidence of an intent to deceive on an issue that was very material to whether the patent was granted or not. Aventis argued that they used different dosages because when the drugs would be used clinically, they would use different doses. Of course even if that is true, Aventis should have been clear about it in their patent application. In a dissent it was argued that inequitable conduct should be restricted to only the most extreme cases of fraud and deception.