Watch Your Mouth - Therasense, Inc. v. Becton, Dickinson & Co.,

The US federal circuit has now issued an en banc decision on inequitable conduct in the case Therasense, Inc. v. Becton, Dickinson & Co.,.

The case was related to a patent (US 5,820,551) on an electrochemical sensor for testing whole blood (i.e. blood with all its natural ingredients) comprising an electrode. The new thing was that the electrode was not covered by a membrane, whereas there the prior art allegedly relied on the technical prejudice that covering the electrode with a membrane is necessary to prevent some ingredients of the blood from sticking to the surface of the electrode. The inventors have apparently found a way to circumvent the necissity of that membrane.

The closest prior art US 4,545,382 ("the '382 patent") discloses that "Optionally, but preferably when being used on live blood, a protective membrane surrounds both the enzyme and the mediator layers, permeable to water and glucose molecules.”

In order to support the argument that the latter passage did not clearly teach a device without a protective membrane, the applicant's director for R&D, Dr. Sanghera submitted a declaration to USPTO stating:
"[O]ne skilled in the art would have felt that an active electrode comprising an enzyme and a mediator would require a protective membrane if it were to be used with a whole blood sample. . . . [O]ne skilled in the art would not read lines 63 to 65 of column 4 of U.S. Patent No. 4,545,382 to teach that the use of a protective membrane with a whole blood sample is optionally or merely preferred."

Now, the problem starts with the fact that the prior art '382 was held by the applicant of the case under dispute and that the applicant's declarations in this older application were in contrast with Dr. Shanghera's declaration mentioned above.

However, in the EP counterpart of the '382 (the prior art of the case at issue), the applicant's EP representative had argued as followed:
"It is submitted that this disclosure is unequivo-cally clear. The protective membrane is optional, however, it is preferred when used on live blood in order to prevent the larger constituents of the blood, in particular erythrocytes from interfering with the electrode sensor. Furthermore it is said, that said protective membrane should not prevent the glucose molecules from penetration, the membrane is “permeable” to glucose molecules. This teaches the skilled artisan that, whereas the [D1 membrane] must . . . control the permeability of the glucose . . . the purpose of the protective membrane in the patent in suit is not to control the permeation of the glucose molecules. For this very reason the sensor electrode as claimed does not have (and must not have) a semipermeable membrane in the sense of D1." (D1 is another piece of prior art)

This discrepancy (i.e. a discrepancy between declarations given in different procedures relating to different patent applications) and the fact that the submissions of the EP representatives in the EP counterpart of the '382 patent had not been disclosed to the USPTO led to a judgement of a california district court holding the patent unenforceable for inequitable conduct, which was upheld by the Federal Circuit in 2010.

Although the Federal Circuit has finaly vacated the district court's finding of inequitable conduct and has remanded by further proceeding, this case appears to have a big impact on our practice as EP representatives because not only it is clear that our comments on the construction of prior art documents could be used against our clients in the US if the same prior art document is cited in a co-pending or completely unrelated application but also that there may be a duty to disclose these comments as soon as the same documents is cited again. This is a difficult task because, in priciple, it requires keeping track of all the citations of the entire patent portfolio and disclosing all the comments on that document as soon as the document is cited again in another applicaion.