A new prescription for negative claim limitations

In a unique case, the CAFC reversed its decision on a patent infringement and raised the standard for written descriptions of negative claim limitations. By Hailey Bureau of BSKB.

In a rare move, the Court of Appeals for the Federal Circuit (CAFC) recently reversed its previous ruling for Novartis Pharmaceuticals Corp, now holding that a negative limitation in the claims of Novartis’ patent lacked written description, in Novartis Pharms Corp v Accord Healthcare (Fed Cir, June 21, 2022).

Previously, in a precedential January 2022 decision, the CAFC affirmed the United States District Court for the District of Delaware holding that the patent for Novartis was not invalid and was infringed by HEC Pharm Co.

Upon granting a request for rehearing, the CAFC vacated its precedential January 2022 decision, and reversed the district court’s judgment that Novartis’ claims are not invalid for inadequate written description. In its most recent precedential decision in June 2022, the CAFC raised the standard for demonstrating adequate written description for negative claim limitations by requiring that the limitation in question be “necessarily excluded” in the specification.

Negative limitations

Title 35 USC § 112(a) requires that “the specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor or joint inventor of carrying out the invention.”

This creates two separate requirements referred to as enablement and written description. The specification must describe the invention such that a person having ordinary skill in the art would understand that the inventor actually possessed the invention claimed and the specification must sufficiently disclose how to make and use the invention. Ariad Pharms v Eli Lilly & Co (Fed Cir, 2010) (en banc).

Typically, a claim defines an invention by what it is, rather than by what it is not. In other words, the invention is described by “positive limitations” to define the elements of the claim. However, US patent laws allow for “negative limitations” to be used in drafting a claim. A simple example of a negative limitation would be “wherein the solvent is not water.” The negative limitation is an express exclusion of an element as a feature of the claim. In essence, a negative limitation defines the invention by what it is not.

The patent being challenged is US patent No. 9187405 (the ‘405 patent), owned by Novartis, and is directed to methods of treating relapsing-remitting multiple sclerosis using the immunosuppressant fingolimod. Novartis markets a drug product covered by the patent under the brand name ‘Gilenya’. HEC filed an abbreviated new drug application (ANDA) with the US Food and Drug Administration seeking approval to market a generic version of Gilenya, which triggered Novartis to sue HEC in district court, asserting that HEC infringes the ’405 patent.

“The court finds that for an element to be excluded from the scope of a claim via a negative limitation, the specification must ‘necessarily exclude’ the element.”

Hailey Bureau, BSKB

Claim 1 of the ‘405 patent recites, “A method for reducing or preventing or alleviating relapses in relapsing-remitting multiple sclerosis in a subject in need thereof, comprising orally administering to said subject 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol, 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.” The limitation of “at a daily dosage of 0.5 mg, absent an immediately preceding loading dose regimen” was added to the claim during prosecution and is the negative limitation at issue.

The district court held that HEC infringes the patent and that the patent is not invalid, finding that the limitation of “at a daily dosage of 0.5 mg, absent an immediately preceding loading dose regimen” met the written description requirement.

HEC appealed that decision to the CAFC, which subsequently affirmed the judgment of the lower district court in January 2022. The CAFC granted the rehearing, and vacated the January 2022 decision, holding that the district court clearly erred in holding that the negative limitation is supported by the written description of the specification.

Silence is inadequate

In arriving at the reversal, the court noted that the ’405 specification does not discuss the presence or absence of a loading dose. Because of this silence, the court takes the position that this does not support the negative limitation that precludes loading doses. In the court’s view, the issue is whether the specification precluded the use of a loading dose. On this, the court finds that the evidence is lacking to demonstrate that a person having ordinary skill in the art would understand that the silence regarding the loading dose in the specification would “necessarily exclude” a loading dose.

The majority states that “If it were, then every later-added negative limitation would be supported so long as the patent makes no mention of it. While a negative limitation need not be recited in the specification in haec verba, there generally must be something in the specification that conveys to a skilled artisan that the inventor intended the exclusion, such as a discussion of disadvantages or alternatives.”

For the first time, the court finds that for an element to be excluded from the scope of a claim via a negative limitation, the specification must “necessarily exclude” the element.

In his dissent, Judge Linn takes the position that the majority elevated the written description standard to require not only a “reason to exclude” but also a showing that the negative limitation is “necessarily excluded”.

Judge Linn’s perspective is that requiring that the limitation be necessarily excluded goes too far. In relying on Ariad, Judge Linn points out that the standard for a negative limitation is no different than for a positive limitation, in that the written description must reasonably convey to those skilled in the art that the inventor had possession of the claimed subject matter as of the filing date of the application.

In relying on prior case law, Judge Linn points out that a negative limitation is not “fatal” if a person having ordinary skill in the art would have understood when reading the specification that the negative limitation reflects what the specification shows has been invented.

Judge Linn’s position is the majority posed the wrong question, which lead to the incorrect finding stating that, “The question is not whether the patentee precluded the use of a loading dose but whether the claim language that precludes the administration of a loading dose is supported by the written description passages that disclose the effective administration of nothing more than a ‘daily dose’.”

Changing views

Not only does this decision raise the standard for written description support for negative limitations, but it also raises a unique procedural issue. The January 2022 decision consisted of a three-judge panel: Judge O’Malley, Judge Linn, and Chief Judge Moore (dissenting). Judge O’Malley penned the majority opinion.

Then, Judge O’Malley retired and was replaced on the panel by Judge Hughes. HEC requested a rehearing, on which Judge Hughes (not on the original panel) agreed with Chief Judge Moore (originally dissenting) that a rehearing should be ordered. In the present decision, Chief Judge Moore writes the majority opinion with Judge Linn as the dissent.

It is an extremely rare occurrence for the CAFC to grant a rehearing at all, let alone grant a rehearing and reverse its prior precedential decision. This procedure also highlights the issue that a member of the original majority in the January 2022 decision was not required to agree with the decision to grant the rehearing. There may be concerns for future litigants to consider when deciding whether to appeal to the CAFC since the shuffling of the panel appears to have resulted in such inconsistent viewpoints on the law.

Immediately following the decision, Novartis filed a petition for panel and en banc rehearing on July 21, 2022. In its petition, Novartis raised two issues for reconsideration: (1) the retirement of one judge after the panel decision should not have reversed the outcome of the prior January 2022 decision; and (2) the June 2022 decision created a new standard for written description support for negative limitations. Several amicus briefs were filed in support of granting en banc review. En banc review was denied in a brief decision issued on September 20, 2022. Novartis now plans to seek review by the US Supreme Court.

Hailey Bureau is an associate with BSKB. Bureau’s practice focuses on patent prosecution specialising in chemistry and life sciences. She can be contacted at:

Images: Shutterstock / Hernan E. Schmidt

Issue 3, 2022

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