Notwithstanding the rigorous test for proving inequitable conduct established by the en banc U.S. Court of Appeals for the Federal Circuit last May in its Therasense decision (see IP Update, Vol. 14, No. 6), the Federal Circuit upheld a district court decision finding that the patents covering Aventis Pharma’s blockbuster anti-cancer drug Taxotere were unenforceable due to inequitable conduct.  Aventis Pharma S.A. v. Hospira, Inc., Case No. 11-1018 (Fed. Cir., Apr. 9, 2012) (Prost, J.). 

The patents in question cover intravenous formulations of Taxotere as delivered in a diluted aqueous solution called a “perfusion.”  The patented formulation was designed to overcome stability and toxicity problems in a prior formulation by use of a different surfactant  and by limiting the amount of ethanol as compared to prior art formulations.  

The district court concluded that specific claims of each of the Aventis patents were invalid for obviousness, not infringed and unenforceable.  In terms of its decision on inequitable conduct, the district court (in a pre-Therasense ruling) made separate and distinct findings on intent and materiality, finding that two prior patents were material to patentability and that the inventor intentionally withheld them intending to deceive the U.S. Patent and Trademark Office (PTO).  Aventis appealed.  

In Therasense, the Federal Circuit rejected the “sliding scale” approach to proving inequitable conduct “where a weak showing of intent may be found sufficient based on a strong showing of materiality, and vice versa” and held that “[i]ntent and materiality are separate requirements.”   As for materiality, the Therasense Court held that “but-for materiality is the standard for evaluating the materiality prong of the analysis unless there is affirmative egregious misconduct.”  In affirming the district court, the Federal Circuit that “although the district court did not have the benefit of our Therasense opinion when it rendered its inequitable conduct decision, the [district] court nevertheless found that the withheld references were but-for material to patentability and made distinct intent and materiality findings rather than employing the now-abrogated sliding scale approach.”  

Aventis argued on appeal that the inventor had explained why he did not disclose the references to the PTO and that the district court’s finding that he acted with the intent to deceive “was not the single most reasonable inference that could be drawn from the evidence.”  Additionally, Aventis contended that the withheld references were not material because they were duplicative of references already before the PTO.  


After explaining that the standard for establishing “but-for materiality” in the inequitable conduct context requires only “a preponderance of the evidence, giv[ing] claims their broadest reasonable construction,” the Court made short work of Aventis’ materiality argument noting that, “when a claim is properly invalidated in district court based on the deliberately withheld reference, then that reference is necessarily material for purposes of the inequitable conduct inquiry.”


The Federal Circuit, after reiterating that in order to satisfy the Therasense intent requirement, “the accused infringer must prove by clear and convincing evidence that the applicant knew of the reference, knew that it was material, and made a deliberate decision to withhold it,” nevertheless concluded that Hospira had met its burden.

Giving due regard to the district court’s credibility determination, the Federal Circuit concluded that the district court's finding that the inventor acted with a specific intent to deceive the PTO in “withholding those references is not clearly erroneous.”  At trial, the inventor testified that he considered his prior art work a “failure” and that he therefore believed he did not need to disclose it to the PTO.  Aventis argued that based on this testimony the court erred in finding that the inventor “had the specific intent to deceive the PTO because the finding was not the single most reasonable inference that could be drawn.”

However, noting the totality of inventor’s testimony, including his testimony that his prior experiments (reported in the withheld reference) was one of the “main factors that shaped [his] thinking” in choosing a surfactant for the claimed invention, the Federal Circuit concluded the district court was justified in finding the inventor’s explanation to not be credible, especially since the inventor disclosed to the PTO other prior art that presented the problem he was attempting to solve (without disclosing a possible solution).

Practice Note:  In this case, since the district court’s invalidity findings were affirmed (based on a clear and convincing evidence standard), satisfaction of the materiality prong (based on the preponderance standard) was a forgone conclusion. 

On a related note, the remand to the district court in the Therasense case that gave rise to the en banc Federal Circuit decision has now resulted in a ruling that even under the far stricter test now in effect, the Therasense patent is unenforceable due to inequitable conduct.  Therasense v. Becton Dickinson, Case No. 3:04-cv-02123-WHA (ND Cal., March 27, 2012) (Alsup, Distr. J.).  In the remand decision, the court found that the withheld briefs were material under the “but for materiality” test and that the persons who withheld it did so with the specific intent to deceive the PTO. Early on his decision, in reference to the Federal Circuit’s Therasense decision, Judge Alsup seems to question the wisdom of an inequitable conduct standard under which “an applicant or his attorney may knowingly and deliberately withhold from the PTO any reference known to be inconsistent with a position taken by him or her before the PTO so long as the withholder does not know that the reference itself would lead to a rejection.”