Although the stringent “but for” test of materiality of Therasense has made it difficult to show inequitable conduct, in Apotex, Inc. v. UCB, Inc., 2013-1674 (Fed. Cir. 2014) the Federal Circuit affirmed a finding of inequitable conduct.  After finding materilaity, i.e., that thepatent would not have been allowed but for misconduct, the Federal Circuit went out of its way to point out that there is no duty to disclose suspicions or beliefs regarding the prior art.  The Federal Circuit said that there is nothing wrong with advocating, in good faith, a reasonable interpretation of the teachings of the prior art.  However the Federal Circuit found that the misconduct at issue, however, goes beyond failing to disclose a personal belief or alternative interpretations of the prior art; but consisted of affirmatively and knowingly misrepresenting material facts regarding the prior art.  In fact, the Federal Circuit found that the case comes close to the type of affirmative misconduct that in Therasense we held could justify finding inequitable conduct without showing but-for materiality.  The Federal Circuit found the conduct conduct evidences a pattern of lack of candor, and agreed with the district court that deceptive intent was the single most reasonable inference that can be drawn from the evidence.