## Facts

- Aventis owned patents covering low molecular weight heparin (LMWH) compositions used as anticoagulants and marketed as Lovenox/Clexane.
- During prosecution, the examiner rejected claims over prior art, including a European patent (EP ’144), for anticipation and obviousness.
- To obtain allowance, Aventis relied heavily on declarations by Dr. André Uzan asserting Aventis’s LMWH had a longer half-life at a 40 mg dose and provided clinically meaningful advantages, including supporting unexpected results over EP ’144.
- The declarations presented half-life comparisons but did not disclose the dose administered for the EP ’144 product in the comparative testing.
- Evidence later showed the comparison used different doses and that when Aventis’s LMWH and the EP ’144 product were compared at equal doses, the half-life difference was minimal.
- Aventis sued Amphastar for infringement; Amphastar asserted inequitable conduct based on the omission of the EP ’144 dosage information.
- In a prior appeal, the Federal Circuit held the withheld dosage information was material and remanded for findings on intent.
- After a bench trial on remand, the district court found intent to deceive and held the patents unenforceable; Aventis appealed.

## Issues

1. Whether the district court clearly erred or abused its discretion in finding inequitable conduct based on intentional withholding of material dosage information underlying comparative half-life data submitted to the USPTO.
2. Whether clear and convincing evidence supported the finding that Aventis acted with intent to deceive the USPTO.

## Decision

- The Federal Circuit affirmed the judgment of unenforceability for inequitable conduct.
- Materiality was established because the omitted dosage information bore directly on the half-life comparisons that were central to overcoming prior art rejections.
- The district court did not clearly err in finding intent to deceive, relying on strong materiality, the misleading impression of an equal-dose comparison, and the lack of a credible innocent explanation for the omission.
- Aventis’s arguments that the examiner would have requested the dose, or that the declarations implicitly conveyed dose differences, did not defeat the intent finding.
- The asserted patents were unenforceable, defeating Aventis’s infringement claims.

## Legal Principles

- Inequitable conduct requires clear and convincing evidence of (1) materiality of the withheld or misrepresented information and (2) intent to deceive the USPTO.
- Materiality and intent may be evaluated on a sliding scale; stronger materiality can reduce the amount of additional evidence needed to infer intent, though intent cannot be inferred from materiality alone.
- Intent may be inferred from circumstantial evidence, including misleading presentation of comparative data, omission of key experimental conditions, and implausible or non-credible explanations for nondisclosure.
- Applicants have a duty of candor; an examiner’s failure to request specific details does not excuse withholding information that is important to evaluating patentability.

## Conclusion

The Federal Circuit affirmed that Aventis’s patents were unenforceable because Aventis secured allowance by submitting comparative half-life evidence while withholding the prior art dosage used in those comparisons, and the record supported a finding—by clear and convincing evidence—of both materiality and intent to deceive the USPTO.


Aventis Pharma S.A. v. Amphastar Pharms., Inc., 525 F.3d 1334 (Fed. Cir. 2008)