The Federal Circuit has recently affirmed a Northern District of California decision finding, among other things, U.S. Patent No. 5,820,551 (the ‘551 patent) unenforceable due to inequitable conduct. Therasense, Inc. v. Becton, Dickinson and Co., Case No. 2009-1511 (Fed. Cir. 2010). During prosecution before the U.S. Patent and Trademark Office (USPTO), the ‘551 patent was rejected on prior art grounds. In order to avoid the rejection, the Applicant submitted a declaration attesting that the cited prior art’s disclosure of an element being “optionally, but preferably” present in the disclosed device would be interpreted by one of ordinary skill as being “required”. The Applicant then failed to disclose to the USPTO statements made by the Applicant to the European Patent Office (EPO) in a related European application. During a proceeding before the EPO, the Applicant argued that the identical prior art language was “unequivocally clear” that the particular element was “optionally utilized” in the disclosed device. The Federal Circuit found that the Applicant violated its duty of disclosure for failing to make the USPTO aware of the contrary position presented to the EPO.

As a result of the Therasense decision, inventors and their patent attorneys should be mindful of the assertions made to the USPTO and patent offices abroad. In the event contrary representations are made to another forum, an Applicant should consider whether the USPTO should be made aware of the statements.