IP Briefs: The Positive Side of Negative Disclaimers

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BioPharm International, BioPharm International-06-01-2007, Volume 20, Issue 6

Addition of a disclaimer to a claim, based on words not present in the application as filed, is referred to as an undisclosed disclaimer.

Biopharmaceutical and pharmaceutical companies rely on patent protection of proprietary compounds to ensure an exclusive market position after approval to market the compound. Typically, a company will file a patent application on the compound or on a number of candidate compounds well before clinical studies begin, and sometimes before a single compound is identified for clinical development.

When preparing an application for filing, the company's patent attorney conducts a search of the patent and scientific literature, to evaluate whether the candidate compounds have already been described in the literature, and are thus unpatentable. As any patent attorney will admit, however, it is impossible to identify every possible document that may bear on patentability of the candidate compounds for two reasons. First, no search can be exhaustive of the patent and scientific literature worldwide. Second, most patent applications are published 18 months after filing with the US Patent and Trademark Office. This means that a patent publication that may render one or more of the company's candidate compounds unpatentable for lack of novelty may not be publicly available at the time the patent attorney conducts the patentability search and files the company's patent application. Thus, short of having a crystal ball, any assessment of patentability is imperfect.

Years after filing the patent application, a patent examiner will be assigned to the application to opine on the patentability of the pending claims. The patent examiner will conduct a search of the scientific and patent literature, which will now include patent application publications that were not yet published when the patent attorney conducted the patentability search years before, i.e., patent applications filed before, but published after, the filing date of the company's patent application. If a patent publication is identified by the examiner that describes one or more of the claimed candidate compounds, the applicant is faced with an unpleasant surprise—any pending claims that include a compound described in the newly identified publication are deemed unpatentable for lack of novelty.

This article considers the use of a tool called a negative disclaimer, or more simply, a disclaimer, as an approach for dealing with these unexpected surprises. We review the admissibility of disclaimers in the US and in Europe as a means to restore novelty to a claim rejected over a document that was not publicly available, or was unknown to the patent attorney at the time of filing the patent application.


Consider the claims in US Patent No. 6,989,366. Claim 1 is to a method for reducing food intake in a subject desirous or in need of reducing food intake. The method involves administering an amount of an exendin agonist effective to reduce food intake, wherein the exendin agonist is an exendin peptide analog. Claim 15 specifies that the exendin agonist is an exendin peptide analog having a certain generic sequence, with the proviso that the exendin peptide analog is not exendin-3 or exendin-4. The language set forth in italics is a disclaimer and has the effect of excluding from the scope of the claim the peptides known as exendin-3 and exendin-4.



The concept of using a negative disclaimer in a claim to distinguish over the prior art first appeared in the US legal system over 30 years ago.1 In a chemical case before the court, a pending claim had been amended to recite "said homopolymer being free from the proteins, soaps, resins, and sugars present in natural Hevea rubber" in order to exclude previously disclosed elements in the art. The court found the disclaimer permissible, because each recited limitation in the disclaimer was definite. In another case,2 the court found that the negative disclaimer "incapable of forming a dye with said oxidized developing agent" was definite because the boundaries of the patent protection sought were clear.

In these cases, the literal words used in the negative disclaimer were not present in the application as filed. Addition of a disclaimer to a claim based on words not present in the application as filed is referred to as an undisclosed disclaimer.

Several other US cases also suggested that the law favored allowing applicants to insert undisclosed disclaimers into patent claims. In 1977, the court stated that the idea that one who fully discloses and teaches how to make and use a genus and numerous species therein, has somehow failed to disclose that genus minus two of those species, was said to result in an overly-legalistic application of the law.3 In holding that to deny applicants the ability to narrow claims to a subgenus simply because there is no express support in the specification would be to demand that patent applicants be all knowing and foretell what prior art be cited so that they can layer their claim scope accordingly throughout the disclosure. Applicants would have to "either prophetically divine what the art contains, or they must lay down a barrage of claims, starting with the widest and proceeding by the successive incorporation of more and more detail, until all combinations have been exhausted."4

Despite these early cases holding that undisclosed disclaimers are permissible, the law today has changed, making it more difficult to add an undisclosed disclaimer to pending claims in a US application. In finding that addition of a negative disclaimer to a pending claim introduced concepts not described in the application as originally filed, the court in 1984 established that any negative disclaimer or exclusionary proviso had to find support in the patent application as filed.5 Indeed, this is the rule currently applied by patent examiners in the US, where a negative disclaimer which does not have basis in the application as filed is generally impermissible.

However, two non-precedential cases in 1996 seem to soften this approach. In one case, a decision to permit addition of a disclaimer to the claims was permitted because the application as originally filed suggested that the applicant possessed the idea of the invention absent the disclaimed subject matter.6 In the other case, the patent applicant was able to expressly limit the claims so that they included only a portion of the whole invention, on the grounds that a description of the whole invention in the application as filed also describes a portion of the whole invention.7 These cases suggest that an applicant in the US may use a negative disclaimer that is not expressly set forth in the application at the time of filing in situations where the application as filed conveys that selected portions of the invention may be excised.


The European approach is more thoughtful, and perhaps more enlightened. In 2004 a ruling body8 in Europe held that disclaimers may be allowable in certain situations, including to restore novelty by delimiting a claim against (i) a patent application that was filed, but unpublished, at the time of applicants filing and (ii) an "accidental anticipation."

The first case, point (i), is the situation noted above in the introductory paragraphs. Specifically, in the situation where a patent examiner identifies a patent publication that was filed at a patent office, but not yet published, at the time of filing the applicant's patent application, a disclaimer can be added to the claims to exclude the subject matter set forth in the prior art patent publication. This is a sensible rule, since the applicant at the time of filing her application could not have known about the subject matter set forth in the earlier filed document because it had not yet been published. It is disappointing that the US patent system does not provide for a similar, sensible approach to restore novelty to a patent claim by subtracting from its claim scope the subject matter in the prior art patent publication.

With respect to situation (ii), an "accidental anticipation" refers to a document that is "so unrelated and remote that the person skilled in the art would never have taken it into consideration when working on the invention."9 A disclaimer to excise the prior material from the scope of the pending claim is permitted in this situation. For example, consider a patent claim to a group of chemical compounds, small molecules or peptides, for use in treating cancer. Suppose a single compound falling within the claimed group of compounds is described for a completely different use, e.g., developing photographic film, in an "accidental" anticipatory document. The European patent office acknowledges that it would be unfair to bar patenting the use of the entire group of compounds for treating cancer simply because the application as filed did not contain basis for a limiting amendment excluding the irrelevant use, developing photographic film. On these facts, the applicant would be allowed to include a disclaimer in the pending claims to remove from the scope of the claims use of the single compound in developing photographic film.

Another example illustrates a situation where an accidental anticipation was found not to exist. In this case, compounds in the anticipating document were described as "good therapeutics" and as having "valuable therapeutic properties" while the claimed compounds were "for use as a medicament."10 Reasoning that this was not a case of accidental anticipation because the anticipatory document belonged to the same technical field as the claimed invention, a disclaimer to the compounds described in the anticipatory document was not permitted.


In the US, addition of a disclaimer to a pending claim to excise subject matter from an earlier-filed document is generally impermissible. There is a slim chance of adding a disclaimer, if the application as filed conveys the inventor contemplated the invention absent the excised subject matter. In practice, this means drafting the application to describe that some of the invention's embodiments, e.g., certain compounds, can be excluded from the claim scope. This is perhaps most easily achieved by including a statement in the application that the invention includes any combinations or subcombinations of any of the compounds disclosed in the application, such as "it is intended that the appended claims be interpreted to include all modifications, permutations, additions and sub-combinations as are within the true spirit and scope of the embodiments discussed." It can also be achieved by explicitly reciting various combinations of the compounds, the various combinations composed of all but one or more of the compounds.

In Europe, the possibility of adding a disclaimer to avoid prior subject matter is more generous. A disclaimer can be added to a claim to excise subject matter that could not have been known at the time of filing a patent application, either because the subject matter was in a document filed at a patent office but not yet published, or was in a document so completely irrelevant to the applicant's field of invention that it constitutes an accidental anticipation.

In summary, disclaimers in the US and in Europe offer a possible, but not a certain approach to restore novelty to a claim rejected over a document that was not publicly available or was unknown to the inventors or patent attorney at the time of filing the patent application. The European patent system is more lenient and will permit a disclaimer in defined situations. The US patent system is less forgiving, and addition of a disclaimer is not likely to be permitted, unless basis for the disclaimer can be found in the application as originally filed.


1. In re Wakefield, 164 USPQ 636, 638, 641; 422 F.2d 897, 899, 904 (CCPA 1970).

2. In re Barr, 170 USPQ 330; 444 F.2d 588 (CCPA 1971).

3. In re Johnson, 194 USPQ 187, 196; 558 F.2d 1008, 1019 (CCPA 1977).

4. In re Driscoll, 195 USPQ 434, 438; 562 F.2d 1245, 1249 (1977).

5. Ex parte Grasselli, 231 USPQ 395; 738 F.2d 453 (Fed. Cir. 1984).

6. Ex parte Parks, 30 USPQ2d 1234, 1236 (Bd. Pat. App. & Inter. 1993).

7. Ex parte Shalati, 1996 WL 1771413 (Bd. Pat. App. & Inter. 1996).

8. Enlarged Board of Appeal Decision G1/03 (OJ 2004, 413) and G2/03 (OJ 2004, 448); http:// legal.european-patent-office.org/dg3/biblio/g030001ex1.htm and http://legal.european-patent-office.org/dg3/biblio/g030002ex1.htm.

9. G1/03

10. Vertex Pharmaceuticals, Inc. v. Guilford Pharmaceuticals, Inc., (T134/01 2005); http://legal.european-patent-office.org/dg3/biblio/t010134eu1.htm.

Judy M. Mohr, PhD, is a partner with Perkins Coie LLP, Menlo Park, CA, 650.838.4402, jmohr@perkinscoie.com.

Gina Freschi is an associate at Bozicevic, Field & Francis, LLP, Palo Alto, CA, 650.327.3400, freschi@bozpat.com.