Federal Circuit Finds Inequitable Conduct For Failure To Cite Prior Art Under the Heightened Therasense Standard

April 9, 2012

What This Means To You

  • Provide all prior art references that may have led to the conception or reduction-to-practice of the claimed invention to the US Patent and Trademark Office (USPTO).
  • At allowance, closely scrutinize whether any non-disclosed prior art meets the heightened “but-for” materiality standard of Therasense.


In Aventis Pharma v. Hospira, the US Court of Appeals for the Federal Circuit (Federal Circuit) affirmed a district court holding that two Aventis follow-on patents encompassing polysorbate-Taxotere® perfusion formulations invalid for inequitable conduct. This case marks the first time the Federal Circuit applied the heightened inequitable conduct standard post-Therasense.

Case Background

After Hospira and Aventis applied for FDA approval to market generic polysorbate-Taxotere® perfusion formulations, Aventis filed suit in the District Court of Delaware for their infringement of follow-on U.S. Patents 5,750,561 (the ’561 patent) and 5,714,512 (the ’512 patent). On September 27, 2010, the district court, having considered the entire record, concluded all asserted claims of the patents-in-suit were invalid for obviousness, and both patents were unenforceable due to inequitable conduct.

Inequitable conduct occurs when a patent applicant intentionally and materially misleads the USPTO, and both intent and materiality must be proven. The most typical inequitable conduct allegation is failure to notify the USPTO of a known reference that impacts patentability. Over time, the standard for establishing inequitable conduct had lowered to a sliding-scale approach: a lower “should have known” intent element was acceptable against a stronger showing of materiality; a lower “likelihood of materiality” was acceptable against a stronger showing of intent.

After the Aventis district court decision, the Federal Circuit set forth a heightened standard for failure to disclose a prior art reference in Therasense, Inc. v. Becton, Dickinson & Co. The Therasense court first held that an omitted reference is material only if “but for” its exclusion the patent would not have issued. The Therasense court secondly held that there must be proof of a specific knowledge and deliberate intent to deceive, or, if lack of such proof, inference of a specific intent but only if that conclusion is the “single most reasonable inference able to be drawn from the evidence.” The Therasense court further held a sliding-scale approach between the separate elements of intent and materiality should not be applied. Against this backdrop, in April 2012 on appeal, the Federal Circuit considered whether the Aventis district court properly found inequitable conduct consistent with the heightened standard set forth in Therasense.

Decision Analysis

The Aventis Federal Circuit found the circumstances involving non-disclosure of two prior art references met the heightened Therasense standard, and the Aventis district court properly found both patents invalid for inequitable conduct.

The 1989 Dictionnaire Vidal (“Vidal”) describes Sandoz Laboratories experiments with etoposide, noting lack of anaphylaxic side effects when formulated with polysorbate instead of Cremophor®. The inventor Fabre testified Vidal was one of the “main factors that shaped [his] thinking” in choosing polysorbate to formulate Taxotere®. There was also an internal Aventis memo noting Sandoz used polysorbate with some success.

Gueritte-Voegelein et al., J. Med. Chem. (1991) 992-8 (“GV”) is a publication generated from Aventis in-house work, mentioning that Taxotere® showed better solubility in polysorbate than Taxol®. The inventor Fabre initially testified that he had only reviewed an early draft of GV that did not contain this teaching. Fabre later testified that he had, in fact, reviewed the final draft “with some care,” and had later modified a product brochure to include a citation to the published GV.

Establishing “but-for” materiality was not an issue for the Aventis Federal Circuit. The district court found claim 5 of the ’561 patent and claim 7 of the ’512 patent invalid as obvious over Vidal and GV. When a claim is properly invalidated in district court based on a deliberately withheld reference, then that reference is necessarily material for purposes of the inequitable conduct inquiry. The Aventis Federal Circuit concluded since Vidal and GV were necessarily material under the district court’s higher “clear and convincing standard,” Vidal and GV had to be but-for material under the USPTO’s lower “preponderance of the evidence” standard.

The Aventis Federal Circuit also had no difficulty inferring inventor Fabre had a specific intent to deceive by not providing Vidal and GV to the USPTO. The district court judge considered inventor Fabre lacked credibility based on inconsistent testimony, and that he had learned valuable information from the references.

The Aventis Federal Circuit confirmed the elements of inequitable conduct were met under the new Therasense standard, and that the ’561 and ’512 patents were obtained through inequitable conduct.


Upon filing a patent application, provide all prior art references that may have led to the conception or reduction-to-practice of the claimed invention to the USPTO. This may involve internal discussions amongst anyone associated with the invention, including in-house attorneys, staff, non-inventors, and inventors.

At the time of allowance, re-evaluate whether all prior art has been cited to the USPTO. If there is non-disclosed prior art, closely scrutinize whether such art is “but-for” material under the heightened Therasense materiality standard: if “but-for” its exclusion, the claims would not now be allowed. If there is indecision whether the prior art meets such a standard, the best recourse is not to pay the issue fee, but to file a request for continued examination (RCE), and submit the prior art reference for the Examiner’s consideration.

Alternatively, after the patent has issued, under the new AIA rules, the patentee may request supplemental examination in order for the USPTO to consider, reconsider, or correct information believed material to the patent, such as undisclosed prior art references deemed “but-for” material. Supplemental examination may be a way for a patentee to protect against future claims of inequitable conduct if patent infringement litigation arises.