In In Re Bimeda Research & Development Ltd., the Federal Circuit upheld the decision of the USPTO Patent Trial and Appeal Board (PTAB) that found that a claim that excluded the presence of a specific compound was not supported by a description that excluded a genus of compounds. This case illustrates the challenges of establishing written description for exclusion of specific embodiments.

The Patent At Issue

The patent at issue was Bimeda’s U.S. Patent 6,506,400, which was undergoing ex parte reexamination. The patent is directed to compositions for preventing bovine mastitis by providing a physical barrier within the teat canal to block mastitis-causing organisms. As noted by the Federal Circuit, the patent emphasized that it did not require the use of antiinfective agents such as antibiotics.

Claim 1 as originally granted recited:

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 claims at issue recited that the teat seal canal had an “acriflavine-free” formulation.

The PTAB Decision

The acriflavine claims were rejected under 35 USC § 112, ¶ 1, for lack of written description. As summarized by the Federal Circuit, the Examiner “reasoned  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.” The Examiner also explained that “the ’400 patent’s disclosure failed to describe formulations which … could exclude acriflavine but include other antiinfectives.” 

[T]he specific exclusion of acriflavine introduces a new concept, as [it] implies inclusion of one or more undisclosed antiinfectives other than acriflavine. Such a concept is not supported in the disclosure as originally filed.

The Board affirmed the Examiner’s rejection, agreeing that the specification “failed to demonstrate possession of a formulation that specifically excluded the acriflavine species of antiinfectives,” or possession of ”a formulation which excluded acriflavine but could include other antiinfective agents.”

The Federal Circuit Decision 

Judge Clevenger wrote the opinion for the court, which was joined by Judge Prost. Chief Judge Rader wrote a concurring opinion.

The court upheld the PTAB decision:

Substantial evidence supports the [PTAB decision] because the disclosure is generally inconsistent with a formulation which … excludes acriflavine but could include antibiotics.

The court noted that the specification emphasized the “antibiotic-free” approach of the invention and agreed with the Board that “the ’400 patent’s disclosure is … inconsistent with a claim which “excludes acriflavine, but not the presence of other anti-infectives or antibiotics.”

Chief Judge Rader’s Concurrence

While joining the court’s decision, Chief Judge Rader criticized the PTAB’s focus on a traditional written description “possession” analysis rather than “wrestl[ing] with the fact that the claim at issue (and the patent as a whole) focuses on negative claiming.” 

[T]he specification clearly supports a formulation which excludes all antiinfectives. Acriflavine was a well-known species of antiinfective that had been used in teat seals to treat bovine mastitis for over 75 years. … Some of the Board’s analysis of possession ignored these facts and ignored the nature of the claims.

The Difficulty Of Negative Claiming 

This case illustrates the difficulty of negative claiming. Unless the original specification describes specific carve-outs, an Applicant’s ability to exclude specific subject matter from the claims is limited. One quirk of U.S. patent law is that an Applicant can exclude components or steps that are described as optional, in accordance with MPEP § 2173.05(i). Thus, for example, if Bimeda’s application had stated that acriflavine optionally can be included in its compositions, it would have been able to specifically exclude acriflavine without running afoul of the written description requirement. Perhaps this rule explains the PTAB analysis that troubled Chief Judge Rader.