Claim Drafting Issues for Biotech, Chemical and Pharma Patent Applications, Part II: From Indefiniteness to Negative Claim Limitations, Know Best Practices

“If a claim term has more than one ordinary meaning, it is prudent, if not essential, to define all of the ordinary meanings in the specification.”

claim draftingIn our previous blog post, we covered claim construction, Markush Groups, and dependent claim invalidation. As stated previously, while it is impossible to cover all of the various issues related to claim drafting for biotech, chemical and pharma patent applications, in Part II we will highlight some more of the most common issues that may come up, including changes to the law around indefiniteness; product-by-process and means plus function claims; and negative claim limitations. See Debora Plehn-Dujowich’s presentation at the 2022 IP Watchdog Life Sciences Masters conference for more.


Another recent change in the law impacting claim drafting is in the area of indefiniteness. In 2014, the Supreme Court in Nautilus, Inc. v. Biosig Instruments, Inc., 134 S. Ct. 2120 (2014) overturned the “insolubly ambiguous” test for indefiniteness and replaced it with a “reasonable certainty” standard. Furthermore, in Teva Pharmaceuticals USA v. Sandoz, Inc., No. 2012-1567 (Fed. Cir. June 18, 2015), the Federal Circuit held, applying the new “reasonable certainty” standard, that a claim term that had no default meaning to one of skill in the art and was subject to multiple different meanings was invalid as indefinite. Specifically, the court held that the claim term “molecular weight” could represent any of three different weight measures in the art and that neither the claim itself, the specification, nor the prosecution history specified which of these meanings defined the scope of this term in the claim.

The court stated in the Teva decision that:

“Claim 1 of the ?808 patent recites ‘molecular weight’ without specifying the meaning of that term. The parties agree that ‘molecular weight’ could refer to Mp, Mw, or Mn and they agree that each of these measures is calculated in a different way and would typically yield a different result for a given polymer sample. But the claim on its face offers no guidance on which measure of “molecular weight” the claims cover.”

Following this case, in 2017, in BASF Corp. v. Johnson Matthey Inc. 875 F.3d 1360 (Fed. Cir. Nov. 20, 2017), the Federal Circuit opined on whether functional language in a claim can provide the requisite “reasonable certainty”. In this case, the claim language in question described a chemical reaction performed by a coating in a diesel fuel filtration system, using the phrase “composition…effective to catalyze”. The Federal Circuit held that, in this case, a person of ordinary skill in the art would be reasonably certain as to which chemical reactions would perform the recited function. Therefore, while the inquiry is context-specific, functional language can provide reasonable certainty to the person of ordinary skill in the art as to the meaning of a claim term.

To consider indefiniteness when drafting claims, patent practitioners should review their claims and consider whether a skilled person, in light of the specification, would be reasonably certain about the scope of the claim. If not, then perhaps claim term definitions can be added or revised to provide reasonably certainty. If a claim term has more than one ordinary meaning, it is prudent, if not essential, to define all of the ordinary meanings in the specification. And, functional language may not ultimately be indefinite, but that determination will again rely on the person of ordinary skill in the art and whether such functional language would be clear. If not, the specification should be developed to provide that clarity.

Product-by-Process Claims

Product-by-process claims are not limited to the manipulation of the recited steps. See MPEP 2113. Rather, product by process claims are limited only by the structure implied by the steps.

In re Thorpe was a seminal case that held that determination of a product-by-process claims’ patentability is based on the product itself, and not by the steps of the process:

“[E]ven though product-by-process claims are limited by and defined by the process, determination of patentability is based on the product itself. The patentability of a product does not depend on its method of production. If the product in the product-by-process claim is the same as or obvious from a product of the prior art, the claim is unpatentable even though the prior product was made by a different process.” In re Thorpe, 777 F.2d 695, 698, 227 USPQ 964, 966 (Fed. Cir. 1985)

The Federal Circuit has also held that “[b]ecause validity is determined based on the requirements of patentability, a patent is invalid if a product made by the process recited in a product-by-process claim is anticipated by or obvious from prior art products, even if those prior art products are made by different processes.” Amgen Inc. v. F. Hoffman-La Roche Ltd., 580 F.3d 1340, 1370 n 14, 92 USPQ2d 1289, 1312, n 14 (Fed. Cir. 2009).

However, in the context of an infringement analysis, a product-by-process claim is only infringed by a product made by the process recited in the claim. Id. at 1370 (“a product in the prior art made by a different process can anticipate a product-by-process claim, but an accused product made by a different process cannot infringe a product-by-process claim”).

Means Plus Function Claims

Means plus function claims, or claims invoking 35 U.S.C. §112(f), are often thought of in the context of the computer/software fields, where claiming by function may be more practical than claiming a particular structure. However, means plus function claims are a claim type that the practitioner in the biotech/pharma/chemical arts field may also consider as a strategy that, if done properly, may allow the drafter to capture equivalents of a particular structure, material or act that is disclosed in the specification. The statute reads:

An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.

MPEP 2181(I) sets forth a three-prong analysis for determining whether or not a claim is a “means plus function” claim:

  1. The claim limitation must use the term “mean”, “step” or an equivalent term (e.g., a generic placeholder for such term);
  2. The term from (1) is modified with functional language, typically linked to transitional language, such as “for” or “such that”; and
  3. The term from (1) is not modified by sufficient structure, material or acts for performing the claimed function.

Under the first prong, terms that can be used as a “generic placeholder” instead of the traditional “means for” language can include, for example, “mechanism for,” “module for,” “device for,” “unit for,” “component for,” “element for,” “member for,” “apparatus for,” “machine for,” or “system for”. The absence of the “mean”, “step” or equivalent (generic placeholder) language will trigger a rebuttable presumption that 35 USC § 112(f) does not apply.

Under the second prong, it must be clear that the element in the claims is set forth, at least in part, by the function it performs and not by a structure, material or acts for performing the claimed function. Use of transitional phrases like “for” or “such that” assist with the drafting of the functional language.

Under the third prong, if the “means” term is modified by a sufficient structure, material or acts that form the claimed function, then 35 USC §112(f) will not apply. Indeed, if one of ordinary skill in the art, upon reading the specification, would understand a term to have a sufficiently definite meaning that it is clearly the name for the structure that performs the function, even when the term covers a broad class of structures or identifies the structures by their function, then 35 USC §112(f) will not apply. According to MPEP 2181(I)(C):

To determine whether a word, term, or phrase coupled with a function denotes structure, examiners should check whether: (1) the specification provides a description sufficient to inform one of ordinary skill in the art that the term denotes structure; (2) general and subject matter specific dictionaries provide evidence that the term has achieved recognition as a noun denoting structure; and (3) the prior art provides evidence that the term has an art-recognized structure to perform the claimed function. Ex parte Rodriguez, 92 USPQ2d 1395, 1404 (Bd. Pat. App. & Int. 2009) (precedential). “The standard is whether the words of the claim are understood by persons of ordinary skill in the art to have a sufficiently definite meaning as the name for structure.” Williamson v. Citrix Online, LLC, 792 F.3d 1339, 1349, 115 USPQ2d 1105, 1111 (Fed. Cir. 2015).

Therefore, to use means plus function language in a claim, the specification must set forth adequate disclosure showing what is meant by this functional language. When this is done properly, the broadest reasonable interpretation (BRI) of such a claim will include the structure, material or act described in the specification that performs the entire claimed function and importantly, will also include equivalents of the disclosed structure, material or act. However, if the claim, or the specification, is not drafted properly, indefiniteness rejections can be applied under 35 U.S.C. §112(b) and/or written description rejections can be applied under 35 U.S.C. §112(a). Furthermore, the BRI of a means plus function claim can cause a claim to read on prior art, where not using such language (e.g., just claiming the actual structure, material or act disclosed in the specification) may have been free of the art. Finally, 35 U.S.C. §112(f) requires a combination of elements and therefore, care must be taken not to make the “means for” the only limitation in the claim.

An example of effective means plus function claiming in a pharmaceutical case is illustrated in Ex parte Gleave, Appeal 2012-004973 (P.T.A.B. Jan. 22, 2014). In this case, an original claim to a pharmaceutical composition drafted using more standard drafting techniques, was redrafted to invoke 35 U.S.C. §112(f). Specifically, where the original claim broadly claimed a “therapeutic agent effective to achieve a desired therapeutic benefit, the means plus function claim recited (a) a “means for” performing a specific technical function, and (b) a pharmaceutically acceptable carrier. The specification disclosed particular structures that performed the recited specific technical function and ultimately, the Patent Trial and Appeals Board ruled that the claim therefore covered not only these particular structures, but also equivalents that are effective to perform the same function. Using means plus function language has to be done in a thoughtful manner, but it can be effective.

Negative Claim Limitations

Negative claim limitations are sometimes introduced during prosecution to try to avoid prior art. However, care should be taken to ensure that there is proper support in the specification for any negative claim limitations. In a recent Federal Circuit decision (Novartis Pharmaceuticals v. Accord Healthcare Inc. Fed. Cir. 2022), the court held that the negative limitation “absent an immediately preceding loading dose” added during prosecution to overcome prior art failed to satisfy the written description requirement of 35 U.S.C. §112(a). Claim 1 of the Novartis patent at issue (U.S. Pat. No. 9,187,405) recites:

Claim 1. 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 court explained that for negative claim limitations, there is adequate written description when, for example, “the specification describes a reason to exclude the relevant [element].” Santarus, Inc. v. Par Pharm., Inc., 694 F.3d 1344, 1351 (Fed. Cir. 2012). A reason to exclude an element may be found in statements in the specification expressly listing the disadvantages of using that element, for example. Id, at 1351.

However, according to the court the ‘405 specification “discloses neither the presence nor absence of a loading dose.”

According to MPEP 2173.05(i):

Any negative limitation or exclusionary proviso must have basis in the original disclosure. If alternative elements are positively recited in the specification, they may be explicitly excluded in the claims. See In re Johnson, 558 F.2d 1008, 1019, 194 USPQ 187, 196 (CCPA 1977) (“[the] specification, having described the whole, necessarily described the part remaining.”). See also Ex parte Grasselli, 231 USPQ 393 (Bd. App. 1983), aff’d mem., 738 F.2d 453 (Fed. Cir. 1984).

Therefore, to include a negative limitation in a claim, care must be taken to ensure that it has adequate support in the specification. Support may be in the form of a description of reasons to exclude the element, or it may be in the form of a list of alternative elements. However, the lack of any description of an element in the specification may not be sufficient support for a negative claim limitation excluding the element.

Stay Aware to Stay on Top

The learning process never ends. As the USPTO, the PTAB and the federal courts continue to provide guidance on claim construction and other issues, patent practitioners will have to continue to update their best practices for claim drafting.



Warning & Disclaimer: The pages, articles and comments on do not constitute legal advice, nor do they create any attorney-client relationship. The articles published express the personal opinion and views of the author as of the time of publication and should not be attributed to the author’s employer, clients or the sponsors of

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