Silence is not a description of absence

How to read the ledger below. Each numbered point carries the kind of evidence behind it. ESTABLISHED is stated in the authority's own text, with a locator. IMPLEMENTED is the rule as the authority actually applied it. OBSERVED is carried by a source outside this one. ASSUMED is the drafter's inference, flagged as such and not the authority speaking. Quotations are checked against a cached copy of the primary source by script.

In one paragraph

The Federal Circuit granted panel rehearing in Novartis v. Accord on 21 June 2022, vacated its own earlier decision affirming the district court, and reversed. A claim limitation requiring the absence of a loading dose, added during prosecution to overcome prior art, was not supported by a specification that never mentions loading doses in either direction, because the recognised ways of supporting a negative limitation all require the specification to disclose the excluded element, for instance by listing its disadvantages or distinguishing it from alternatives. The court said it was not creating a heightened standard and left an exception for a specification a skilled artisan would read as inherently excluding the element. Judge Linn dissented.

Reader summary

Every claim required administering the drug at a daily dose "absent an immediately preceding loading dose regimen." That negative limitation was added during prosecution to get around prior art. The specification never mentions loading doses at all, in either direction.

The district court had found that silence supported the exclusion, and reasoned that a prophetic trial describing daily dosing from the start told a skilled artisan no loading dose was given. A prior panel decision affirmed. On rehearing the panel vacated its own decision and reversed.

The rule the court states is straightforward and it is not new: written description needs disclosure, and the recognised routes to supporting a negative limitation all involve the specification saying something about the excluded element. A stated disadvantage of using it. A passage distinguishing it from alternatives. What they share is that the element appears.

The court then does two things that keep this from becoming a bright line. It says silence is generally not disclosure but leaves an exception: if a patentee could establish that skilled artisans would always understand the limitation as necessarily excluded when unmentioned, a silent specification could still suffice. And it says expressly that it is not creating a heightened standard for negative limitations.

Judge Linn dissented, saying the majority did create one by demanding necessary exclusion rather than a reason to exclude. That objection is recorded in Tensions and belongs with any use of this case.

Why this matters when you are drafting

A negative limitation is the highest-risk amendment in the toolkit. Claim 7. The reason to add one arrives with the rejection, and the specification was written before that. Nothing else in a continuation claim has quite that structure.

Check the specification for the excluded element before writing the exclusion. Claims 4 and 5. If the document nowhere mentions the thing being excluded, there is no recognised route to support other than the narrow inherent-disclosure exception in claim 11.

A disadvantage or an alternatives discussion is what you want to find. Claim 4. Those are the two named routes. Note the court's own qualifier at claim 13: the disclosure does not have to rise to disclaimer, so a passage listing drawbacks is enough without any language of surrender.

Do not plan to fill the gap with an expert. Claim 12. Testimony about what a skilled artisan would probably understand from silence is expressly insufficient. The showing that works is that the field always reads silence that way, which is a fact about the art, not about the patent.

When drafting a parent, mention what you might later want to exclude. This is the prospective form of claim 5. A sentence acknowledging an alternative regimen, and why it may be undesirable, is cheap at filing and is the exact material a later negative limitation needs.

Cite this case with its posture. Claim 1. It is a rehearing decision that vacated the same panel's affirmance. The earlier reported decision is not law.

What the authority establishes

[ESTABLISHED, the disposition, and note what it vacates] "We grant HEC's petition for panel rehearing, vacate our prior decision, and reverse the district court's judgment that Novartis' claims are not invalid for inadequate written description." (P. 3.)

[ESTABLISHED, the holding in one clause] "Because the '405 patent fails to disclose the absence of a loading dose, the district court clearly erred in finding that the negative claim limitation" (P. 2.) satisfied section 112(a), a limitation that had been "added during prosecution to overcome prior art". (P. 2.)

[ESTABLISHED, the fact everything rests on] "The patent's specification does not mention loading doses, much less the absence of a loading dose." (P. 3.) Silence in both directions, not an ambiguous passage.

[ESTABLISHED, the recognised routes to supporting a negative limitation] There is adequate written description when, for example, "the specification describes a reason to exclude the relevant" element (P. 5.), which could be found in "statements in the specification expressly listing the disadvantages of using" that element (P. 5.), or in a specification that distinguishes among the element and alternatives to it. (P. 5.)

[ESTABLISHED, and this is the sentence to carry] "The common denominator of these examples is disclosure of the element." (P. 5.) Every safe route requires the excluded thing to appear somewhere in the document.

[ESTABLISHED, the rule stated flatly] "Silence is generally not disclosure." (P. 5.) The court cites the manual for the same proposition: "The mere absence of a positive recitation is not a basis for an exclusion." (P. 5.)

[ESTABLISHED, why the contrary rule would swallow the requirement] "If it were, then every later-added negative limitation would be supported so long as the patent makes no mention of it." (P. 5.) The failure mode is specific to limitations added later, which is what makes this a continuation-practice case.

[ESTABLISHED, what suffices short of verbatim recitation] "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." (P. 5.)

[ESTABLISHED, the prohibition stated as a prohibition] The "written description requirement cannot be met through simple disregard of the presence or absence of a limitation." (P. 6.)

[ESTABLISHED, the exception, which is narrow and real] "While a written description's silence about a negative claim limitation is a useful and important clue and may often be dispositive, it is possible that the written description requirement may be satisfied when a skilled artisan would understand the specification as inherently disclosing the negative limitation." (P. 6.)

[ESTABLISHED, what the exception requires, and it is a high bar] "If, however, a patent owner could establish that a particular limitation would always be understood by skilled artisans as being necessarily excluded from a particular claimed method or apparatus if that limitation is not mentioned, the written description requirement would be satisfied despite the specification's silence." (P. 7.) Always and necessarily, not usually.

[ESTABLISHED, what will not establish it] "When the specification is itself silent regarding a negative limitation, testimony from a skilled artisan as to possibilities or probabilities that the recited element would be excluded would not suffice" (P. 7.), because "If silence were generally sufficient, all negative limitations would be supported by a silent specification." (P. 7.) Expert testimony framed in likelihoods cannot fill the gap.

[ESTABLISHED, the court's own disclaimer] "We do not today create a heightened standard for negative claim limitations." (P. 12.) The required disclosure "need not rise to the level of disclaimer." (P. 12.)

[ESTABLISHED, the closing statement of the rule and its limit] "While silence will not generally suffice to support a negative claim limitation, there may be circumstances in which it can be established that a skilled artisan would understand a negative limitation to necessarily be present in a disclosure. This is not such a case." (P. 12.)

[ESTABLISHED, the review standard, which cuts against reading this broadly] "Whether a claim satisfies the written description requirement is a question of fact that, on appeal from a bench trial, we review for clear error." (P. 4.) And the finding here was that "The district court's finding that the no-loading-dose limitation meets the written description requirement was clearly erroneous." (P. 12.)

[IMPLEMENTED, and it is the most useful thing in the record] Claims 4, 5 and 8 together give a drafting test that does not depend on the outcome: does the specification say anything about the element the claim excludes? Claim 11 says a silent specification can still work, but only on a showing about the field rather than about the patent, which is evidence a drafter cannot create at drafting time.

[ASSUMED, drafter's inference, flagged as such] The exclusion that clears prior art is almost always identified after the art is found, which is after filing. Claim 7 names that sequence as the reason for the rule. The opinion does not discuss continuation practice; the inference is that a negative limitation is the limitation type most likely to be unsupported, because the reason to write it did not exist when the specification did.

Quotations, verified against the source

All from the Federal Circuit's opinion on panel rehearing. Page locators computed from the docket stamp, which numbers the majority and the dissent in one continuous sequence.

"Because the '405 patent fails to disclose the absence of a loading dose, the district court clearly erred in finding that the negative claim limitation" (P. 2.)
"added during prosecution to overcome prior art" (P. 2.)
"We grant HEC's petition for panel rehearing, vacate our prior decision, and reverse the district court's judgment that Novartis' claims are not invalid for inadequate written description." (P. 3.)
"The patent's specification does not mention loading doses, much less the absence of a loading dose." (P. 3.)
"Whether a claim satisfies the written description requirement is a question of fact that, on appeal from a bench trial, we review for clear error." (P. 4.)
"the specification describes a reason to exclude the relevant" (P. 5.)
"statements in the specification expressly listing the disadvantages of using" (P. 5.)
"The common denominator of these examples is disclosure of the element." (P. 5.)
"Silence is generally not disclosure." (P. 5.)
"The mere absence of a positive recitation is not a basis for an exclusion." (P. 5.)
"If it were, then every later-added negative limitation would be supported so long as the patent makes no mention of it." (P. 5.)
"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." (P. 5.)
"written description requirement cannot be met through simple disregard of the presence or absence of a limitation." (P. 6.)
"While a written description's silence about a negative claim limitation is a useful and important clue and may often be dispositive, it is possible that the written description requirement may be satisfied when a skilled artisan would understand the specification as inherently disclosing the negative limitation." (P. 6.)
"When the specification is itself silent regarding a negative limitation, testimony from a skilled artisan as to possibilities or probabilities that the recited element would be excluded would not suffice" (P. 7.)
"If silence were generally sufficient, all negative limitations would be supported by a silent specification." (P. 7.)
"If, however, a patent owner could establish that a particular limitation would always be understood by skilled artisans as being necessarily excluded from a particular claimed method or apparatus if that limitation is not mentioned, the written description requirement would be satisfied despite the specification's silence." (P. 7.)
"We do not today create a heightened standard for negative claim limitations." (P. 12.)
"need not rise to the level of disclaimer." (P. 12.)
"While silence will not generally suffice to support a negative claim limitation, there may be circumstances in which it can be established that a skilled artisan would understand a negative limitation to necessarily be present in a disclosure. This is not such a case." (P. 12.)
"The district court's finding that the no-loading-dose limitation meets the written description requirement was clearly erroneous." (P. 12.)
"applies a heightened written description standard to the facts of this case in requiring not only a" (P. 14.)

Tensions and open questions

The dissent says the majority did what claim 13 disclaims. Judge Linn wrote that the majority "applies a heightened written description standard to the facts of this case in requiring not only a" reason to exclude but a showing that the limitation was necessarily excluded. (P. 14.) Claims 4 and 11 do sit uneasily together on exactly that point, and a practitioner should treat the gap between them as unsettled rather than resolved.

Where the inherent-disclosure exception has teeth is untested here. Claim 11 describes a showing about a whole field. The opinion gives no example of a case where it succeeded, and says only that this is not such a case.

How much disclosure of the element is enough is not quantified. Claim 4 names disadvantages and alternatives; claim 13 says disclaimer is not required. Between those two lies a large space the opinion does not map.

The daily-dosage limitation was never reached. The court expressly declined to reach the second written-description challenge, so this record says nothing about it.

Clear-error review is doing real work in both directions. Claim 15. A district court found support; the panel found that finding clearly erroneous; the dissent would not have. The doctrine as applied is fact-bound even where the rule reads categorical.

What this record does and does not cover

The standard for negative limitations, the inherent-disclosure exception, the application to this record, the court's disclaimer of a heightened standard and the disposition were read end to end, and the dissent was read closely enough to state its objection.

What was NOT read closely, and is therefore outside what this record can support: the pharmacology, the trial record, the prophetic-trial dispute in detail, and the procedural history. This record says nothing about whether the daily-dosage limitation was supported, because the court did not reach it, nor about anticipation. The district court's findings are known here only through this court's account of them.

Currency

This record was verified against its primary source on 2026-08-15. That is a fidelity check: the quotations, locators and attribution are accurate to that source. Whether the authority has since been narrowed, distinguished, abrogated or reversed has not been checked here. Confirm it still stands before relying on it.