Amending to exclude a species via a negative limitation may violate the written description requirement

| August 7, 2013

In re Bimeda Research & Development Limited

July 25, 2013

Panel:  Rader, Clevenger, Prost.  Opinion by Clevenger.  Concurrence by Rader.


The court held a negative limitation to exclude a genus does not provide 112, first paragraph written description support to claim a negative limitation that excludes a species, which species was never mentioned in the application.


Bimeda obtained a patent (“the ‘400 patent”) with the following claim 1:

A prophylactic method of controlling infection in a mammary gland by a mastitis-causing organism, comprising sealing a teat canal of a mammary gland with a seal formulation so as to provide a physical barrier in the teat canal.

The PTO ordered ex parte reexamination of the ’400 patent to reevaluate patentability in light of prior art teachings of teat seal formulations utilizing a physical barrier in conjunction with certain antiinfective agents such as antibiotics and the antiseptic acriflavine.

In the reexamination Bimeda cancelled added new independent claim 32, which recited the steps of original claim 1 and added:  wherein the teat seal canal had an “an acriflavine-free” formulation.

The examiner rejected claim 32 under § 112, ¶ 1, reasoning that “acriflavine” was not mentioned anywhere in the original disclosure of the ’400 patent and so therefore the disclosure did not demonstrate possession of an acriflavine-free composition.

On appeal to the board, the board held:

The disclosure failed to demonstrate possession of a formulation that specifically excluded the acriflavine species of antiinfectives.  And that where the patent’s disclosure describes the exclusion of a broad genus, claims to embodiments which exclude particular species are only supported if the disclosure offers some guidance or “blaze marks” to guide the skilled artisan towards excluding that particular species; and

The Board agreed with the examiner that the disclosure failed to convey the full scope of what was affirmatively claimed by claim 32—namely, a formulation which excluded acriflavine but could include other antiinfective agents.

On appeal to the CAFC, Bimeda argues that the disclosure broadly claims a teat seal formulation utilizing a physical barrier, yet does not expressly exclude any particular antiinfective agents.

Bimeda interprets this as tacit indifference to the presence or absence of specific antiinfectives, and contends that the disclosure therefore supports a claim which excludes one particular antiinfective (such as acriflavine) but permits the use of others (such as antibiotics).

The court noted:

The summary of the invention of Bimeda’s patent describes the invention’s “non-antibiotic approach” to preventing mastitis, and explains how this approach achieves the benefit of “meeting consumer preferences for reducing the levels of antibiotics used in food production.”

The remainder of the disclosure similarly distinguishes the invention due to its ability to prevent mastitis without using antibiotics.

Importantly, the patent discloses that the invention presents “no risk of antibiotic residues after calving,” which seemingly can only be true if the formulation excludes all antibiotics.

The court held that substantial evidence supports the Board’s contrary interpretation because the disclosure is generally inconsistent with a formulation which, like claim 32, excludes acriflavine but could include antibiotics.

In the concurrence, Judge Radar notes that the adequacy of written description must be determined on the facts of each case.


Negative limitations do not per se violate 112, first paragraph.  There is nothing inherently ambiguous or uncertain about a negative limitation.  MPEP 2173.05(i).

A disclosure of a genus does not provide support for an unidentified species.  MPEP 2163.05.II.

Likewise, a disclosure to exclude a genus does not provide support for excluding an unidentified species.  MPEP 2163.05.II.

If negative limitations may be desired, they should be put into the application as originally filed.

Claim language “consisting of” and “consisting essentially” may be used.

Full Opinion

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