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Silence isn’t always golden Patent specification doesn’t adequately describe negative limitation

December 1, 2022
Year End 2022 IP Newsletter

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If at first you don’t succeed, try again. The old bromide proved surprisingly meaningful for a pharmaceutical company challenging a competitor’s patent on a treatment method.

The claim that the patent lacked an adequate written description of the method’s “negative limitation” was initially rejected by a three-judge panel of the U.S. Court of Appeals for the Federal Circuit. But the tables turned when the company requested a rehearing before the panel after one judge retired and was replaced.

Round 1

Novartis Pharmaceuticals holds a patent on a method for treating recurring-remitting multiple sclerosis with fingolimod, sold under the brand name Gilenya. The method, as described in the patent’s claims, doesn’t require a so-called initial loading dose to reach therapeutic levels quickly.

The patent’s specification, however, was silent on the subject of loading doses. A specification is intended to disclose the invention to skilled artisans in the relevant field.

Novartis sued HEC Pharm Company and HEC Pharm USA (together, HEC), alleging that HEC’s abbreviated new drug application for a generic version of Gilenya infringed the patent. The trial court found infringement, agreeing with expert testimony that, were a loading dose required, the patent would say that it should be administered “initially.” The Federal Circuit affirmed that ruling.

But HEC requested a rehearing. At the rehearing, HEC maintained that the patent was invalid because its specification didn’t provide an adequate written description of the invention’s “negative limitation” — that is, the absence of a loading dose.

Round 2

The opinion that resulted from the original appeal rejected HEC’s “attempt to create a new heightened written description standard for negative limitations.” The opinion for the rehearing, however, mirrored the dissent from the original appeal.

It found that disclosure is essential — it is the “quid pro quo” of the patent right to exclude. The court explained that a negative limitation has an adequate written description, or disclosure, when the patent specification describes a reason to exclude the relevant element. The specification could, for instance, include a statement identifying the disadvantages of using that element. Or it could include a discussion of alternatives that distinguishes the element.

The court allowed that a negative limitation needn’t be recited in the specification in the exact language used in the patent claims. But the specification generally must include something that conveys to a skilled artisan that the inventor intends the exclusion.

Notably, the appellate court also conceded that the written description requirement could be satisfied despite a specification’s silence in certain circumstances. For example, if a patentee can establish that a particular negative limitation would always be understood by skilled artisans as being necessarily excluded from a particular invention if the limitation isn’t mentioned, the requirement would be met. The court emphasized, though, that testimony from a skilled artisan about the possibilities or probabilities that the element would be excluded wouldn’t constitute sufficient evidence of this.

Alas, this wasn’t such a case. The Federal Circuit panel found no evidence here that a skilled artisan would understand silence regarding a loading dose to necessarily exclude a loading dose.

The roundup

It’s important to note that the Federal Circuit made clear that it hasn’t created a heightened standard for negative limitations. Rather, as with positive limitations, the hallmark of an adequate written description is disclosure.