Most patent claims describe an invention using positive claim limitations that expressly recite the required elements or features of an invention. Sometimes, however, it is necessary, or desirable, to use a negative claim limitation to expressly specify an invention requires the absence of an element or feature. But when is it allowable to claim the negative?

In Novartis Pharmaceuticals v. Accord Healthcare, HEC Pharm appealed the district court finding that the negative claim limitation “absent an immediately preceding loading dose” in U.S. Patent No. 9,187,405 satisfies the written description requirement of 35 U.S.C. § 112(a).  Initially, the Court of Appeals for the Federal Circuit agreed with the district court. But granting a petition for hearing, the Federal Circuit vacated its prior decision and reversed the district court’s finding in a split decision.

On appeal, “[w]hether a claim satisfies the written description requirement is a question of fact,” which is reviewed for clear error. In these cases, the appellate court “defer[s] to the district court’s findings ‘in the absence of a definite and firm conviction that a mistake has been made.’”

The written description requirement is met when a patent’s specification “reasonably conveys to those skilled in the art that the inventor had possession of the claimed subject matter as of the filing date.” Courts have found that for a negative claim limitation, such as the no-loading-dose limitation, to be allowable, there must be adequate written description to support the claimed absence of the element. If there is clear and convincing evidence the written description is lacking for the negative limitation, the claim is invalid.

This raises the question as to what constitutes adequate written description for the absence of an element. In its Novartis decision, the Federal Circuit states a verbatim recitation of the claim language is not necessary, but “[s]ilence is generally not a disclosure.” The majority point out there are several ways to meet the requirement, but “there generally must be something in the specification that conveys to a skilled artisan that the inventor intended the exclusion.” For example, this could be done through “a discussion of disadvantages or alternatives.”

Alternatively, the Court acknowledges that the written description requirement can be met when a person of skill in the art would understand the specification inherently discloses the negative limitation. The Court, however, cautions that expert testimony “as to the possibilities or probabilities that the recited element would be excluded would not suffice,” because “such testimony could effectively eliminate the written description requirement.” In other words, all negative limitations would be supported if silence combined with expert testimony was enough and the statutory, written description requirement impermissibly would be rendered meaningless as to negative claim limitations. The Court, however, recognized that in certain circumstances a patent owner may satisfy the written description requirement by establishing that a person of skill in the art would understand an element is “necessarily excluded from a particular claimed method or apparatus if that limitation is not mentioned.” The potential for proving inherency lives.

In Novartis, the district court found the no-loading-dose limitation supported because the specification never mentions a loading dose. The district court also found this negative limitation supported because the specification “describes giving a ‘daily dosage of 0.5 … mg’ fingolimod to treat RRMS, started ‘initially.’” The district court interpreted this to mean the dosing regiment begins with administering a daily dosage rather than beginning with a higher loading dosage.

The Federal Circuit’s majority found the district court erroneously relied on expert testimony describing that the regimen required “initially” administering a daily dosage. The Court explained the specification instead states “initially patients receive treatment for 2 to 6 months,” but nowhere refers to “‘initially’ administering a daily dosage.”

Further, the Court points out the specification is silent as to the use of a loading dose. The majority found the district court was clearly erroneous in its reliance on the disclosure of a daily dose in combination with silence as to a loading dose as support for the negative limitation. The Federal Circuit’s majority reasoned that there would have been no need to add the negative limitation “[i]f reciting a daily dosage without mentioning a loading dose necessarily excluded a loading dose.” As a result, the Federal Circuit found the specification did not provide adequate written description for the negative limitation, and the claims are thus invalid.

In reaching its decision, the Federal Circuit’s majority expressly stated “[w]e do not today create a heightened standard for negative claim limitations.” The opinion indicates the Court is merely applying the same written description requirement used for positive claim limitations to negative claim limitations.  In dissent, Judge Linn begs to differ. Judge Linn argues the district court applied the correct standard and reached the correct result.

In sum, if a negative limitation is used to distinguish an invention from prior art, courts will require support for it in the specification. Also, expect the issues of negative limitations to show up again in future court cases, as they are used more often during prosecution to overcome prior art rejections. Stay tuned.