A split panel of Judges O’Malley, Linn and Moore (dissenting) affirmed a district court ruling that the claims of U.S. Pat. No. 9,187,405 met the written description requirement (WDR) of s. 112(a). Novartis Pharmaceuticals v. Accord Healthcare Inc., Appeal No. 2021-1070 (Fed. Cir., Jan. 3, 2022). Claim 1 reads as follows:

A method for [treating] relapses in Relapsing-Remitting multiple sclerosis in  subject in need thereof, comprising administering to said subject [fingolimod] in free form or in a pharmaceutically-acceptable salt form, at a daily dosage of 0.5 mg, absent an immediately preceding loading dose regimen.

This is a Hatch-Waxman dispute in which the generics must prove that the ‘405 patent’s claims are invalid for failure to meet the WDR. Part one of the opinion affirmed that the daily dosage met the WDR since it was explicitly disclosed in a prophetic trial in the specification. In an animal model, termed the EAE model, a dosage if 0.3 mg/kg/week was effective to treat the rats. Although Accord argued that conversion of this dose to a dose in humans of 5 mg/day was “mathematical sleight of hand”, and the conversion parameters were not given in the patent or in this opinion, you can do this conversion by dividing the rat dose by 7 and multiplying the result by 60 (kg body weight of adult human). So Accord’s arguments were of no avail.

More interesting, and the cause of the dissent, is the majority’s rationale for holding that the negative claim limitation of “no preceding loading dose” satisfied the WDR. Neither the specification of the ‘405 patent nor of the priority document discloses this limitation, leaving Novartis to argue that the POSA would recognize that this limitation was implicit in the language used to describe both the EAE study and the prophetic trial. Accord had on its side the maxim that silence about a claim limitation in the specification does not permit the introduction of a negative limitation, to exclude the claim element.

The majority relied heavily on precedent for the proposition that a negative limitation is adequately supported if the specification “describes a reason to exclude the relevant limitation.” At least in some cases, the reason(s) to exclude do not require express articulation, but still must be apparent to the person of ordinary skill in the art. “Written description may take any form, so long as a skilled artisan would read the disclosure as describing the claimed invention.”

This introduction allowed the majority to rely on expert testimony that the POSA would recognize, e.g. in a clinical setting, that silence regarding the loading dose limitation would teach the POSA that no loading step was to be employed. Or, put another way, as one expert testified: “So there are two perfectly logical places that if there was going to be a loading dose, it would have been stated.”

The majority also discussed the language used to describe the clinical trial as suggesting that no loading dose was employed: “[T] district court found that ‘starting with a daily dose plainly implies that there is no loading dose’, as a loading dose is a larger-than-daily dose.”

The dissenting Judge Moore argued that this affirmation would permit making negative limitations out of any claim element. It is her opinion that a negative limitation requires some reason to exclude “such as by listing the disadvantages of some embodiment” of the invention, or even reciting alternative features of the invention. She notes Rivera v. Int’l Trade Comm’n, 857 F.3d 1315, 1322 (Fed, Cir. 2017) for the proposition that the “knowledge of [POSA] may be used to inform what is actually in the specification, but not to teach limitations that are not in the specification, even if those limitations would be rendered obvious by the disclosure.” She closes with a warning: “If silence were sufficient then every later -added negative limitation would be supported as  long as the patent makes no mention of it. This is a fundamental error of law.”

I think that this conclusion’s reach is beyond its grasp. The majority used extrinsic evidence to win its case. However, the next time you plan on adding a negative limitation to a claim during prosecution, consider these views of the WDR and proceed with caution!