In Univ. of Mass v. L’Oréal USA, Inc., No. 21-1969 (Fed. Cir. June 13, 2022), the Court of Appeals for the Federal Circuit (“Federal Circuit”) rejected the district court’s claim constructions, vacated the indefiniteness ruling, and remanded the case for further proceedings.


UMass sued L’Oréal for infringement of U.S. Pat. No. 6,423,327 (“the ’327 patent”) and 6,645,513 (“the ‘513 patent”). Representative claim 1 of the ’327 patent read:

[a] method for enhancing the condition of unbroken skin of a mammal by reducing one or more of wrinkling, roughness, dryness, or laxity of the skin, without increasing dermal cell proliferation, the method comprising topically applying to the skin a composition comprising a concentration of adenosine in an amount effective to enhance the condition of the skin without increasing dermal cell proliferation, wherein the adenosine concentration applied to the dermal cells is 10-4M to 10-7M.

The district court adopted UMass’s construction of the wherein clause (underlined above) that the recited concentration range is “the concentration as it is applied to the dermal cells,” not the concentration of adenosine that is applied to the epidermis (the skin surface). Id. at *5 (emphasis added). Relying on this construction, the district court subsequently held the skin-enhancement clause (in bold above) indefinite, and thus entered its final judgment of invalidity of the asserted claims. Id. at *6. For a more detailed discussion of district court’s ruling, see https://www.finnegan.com/en/insights/blogs/prosecution-first/subjective-terms-require-objective-definition.html.

Federal Circuit

The Federal Circuit, however, rejected the district court’s construction of the wherein clause, reasoning that the claim language is not plain on its face and that the proper interpretation is determined by the specification and the prosecution history. Id. at *8.

The Federal Circuit reasoned that the difference in the objects used after “apply” (“to the dermal cells” compared to “to the skin”) may not necessarily mean different things, because the verb “apply” can cover both direct application (i.e., to the skin surface) and indirect application (i.e., to the sub-surface layer). Id. The Federal Circuit further found that the wherein clause refers to “the adenosine concentration applied to the dermal cells,” which is the language for invoking an antecedent, thereby supporting construing the claim to involve one concentration rather than two. Id. at *9. Finally, the Federal Circuit found that the claims refer to the composition being applied, not the “concentration.” Id. at. *9-10. Therefore, “the concentration applied to the dermal cells” in the wherein clause naturally refers to a number of particles per unit of volume of the adenosine composition before putting it in contact with the dermal cells. Id. at *10.

Turning to the specification and the prosecution history, the Federal Circuit concluded that the concentration in the wherein clause refers to the concentration of adenosine in the composition applied to the skin’s surface. Id. at *11. The Federal Circuit referred to multiple embodiments described in the specification, none of which “specify a measurement of concentration after seepage through the skin into the dermis – much less a measurement of concentration as an amount of adenosine per unit of volume of dermal cells.” Id. Additionally, the prosecution history provided even stronger support for the Federal Circuit’s construction. Id. at *12. For example, to overcome a rejection, the applicants imported the adenosine concentration range from a dependent claim to the wherein clause of issued claim 1. In support of the amendment, the applicants did not say there was any change in where the concentration was to be measured. Rather, they argued that “all [claims] are based on the application of certain concentrations of adenosine to the skin[.]” Id. at *13. The Federal Circuit stressed that this is not a case where the prosecution history must meet the standard of clear and unmistakable disclaimer for overcoming an otherwise plain meaning. Id. at *14. “Because the meaning of the relevant claim language is not plain, . . . we can look to the prosecution history to ‘inform [] the meaning of the disputed claim phrase and address[] an ambiguity otherwise left unresolved.’” Id. at *14 (quoting Personalized Media Communications, LLC v. Apple Inc., 952 F.3d 1336, 1345 (Fed. Cir. 2020)).

By rejecting the district court’s claim construction of the wherein clause, the Court “eliminated an important premise of the indefiniteness determination, warranting vacatur of that determination and remand for further proceeding.” Id. at *7.


Whether claim language has plain meaning and how its meaning should be construed are viewed in the context of the claim as a whole and the patent as a whole, including the prosecution history. “We cannot look at the ordinary meaning of the term … in a vacuum. Rather, we must look at the ordinary meaning in the context of the written description and the prosecution history.’” Id. at *7-8, quoting Medrad, Inc. v. MRI Devices Corp., 401 F.3d 1313, 1319 (Fed. Cir. 2005). In the current case, an apparent change in object did not warrant different interpretations of the term “concentration” in the two clauses, in view of the specification and prosecution history. A patent drafter, however, should still try to avoid such unnecessary ambiguity by keeping the claim language consistent. See Aqua-Aerobic Systems, Inc. v. Aerators Inc., 211 F.3d 1241 (Fed. Cir. 2000) (different phrases interpreted differently, even if the drafter intended them to have the same meaning); Epcon Gas Systems, Inc. v. Bauer Compressors, Inc., 279 F.3d 1022 (Fed. Cir. 2002) (construing “substantially below” and “substantially constant” differently because of what the court found to be “subtle differences” in the way the terms were used in the claim.). In addition, when making amendments to claims, confirm that any later-added language is consistent with the existing language.

This case also serves as a reminder to drafters to stay alert when claims require some kind of measurement. Consider how infringement will be proven right from the start. If there is more than one way to perform a measurement, the specification should explain, for example, which way applies or else indefiniteness may be an issue. See Nautilus, Inc. v. Biosig Instruments, Inc., 134 S.Ct. 2120 (U.S. June 2, 2014); Amgen, Inc. v. Hoechst Marion Roussel, Inc., 314 F.3d 1313 (Fed. Cir. 2003).

Further Thoughts

Another claim drafting consideration would be adding in a functional phrase to describe the skin enhancement clause plus the wherein clause to invoke means-plus-function under § 112(f). For example, adding means-plus-function language in the claims during prosecution or in a continuation application could allow one to reduce the indefiniteness risk.

Section 112(f) is invoked when a claim term fails to ‘recite sufficiently definite structure’ or else recites ‘function without reciting sufficient structure for performing that function.’ See Williamson v. Citrix Online, LLC, 792 F.3d at 1349 (Fed. Cir. 2015). Claim construction of a means- plus-function term involves two steps. First, the court identifies the claimed function. It must be clear that the element in the claims is set forth, at least in part, by the function it performs as opposed to the specific structure, material, or acts that perform the function. See York Prod., Inc. v. Central Tractor Farm & Family Center, 99 F.3d 1568, 1574 (Fed. Cir. 1996). Here, one could recite “a means for enhancing the condition of the skin without increasing dermal cell proliferation.” This phrase recites the function of enhancing the condition of the skin but fails to recite the how or the structure to do so. That is, the phrase would invoke means-plus-function.

Next, the court identifies the structure or act that performs the claimed function. The corresponding structure or act of a means-plus-function limitation must be disclosed in the specification itself in a way that one skilled in the art will understand what structure or act will perform the recited function. See Atmel Corp. v. Information Storage Devices, Inc., 198 F.3d 1374, 1381 (Fed. Cir. 1999).

As already discussed above and as highlighted by the Federal Circuit, here, the specification and prosecution history provided ample support directed to the structure or acts that perform the claimed function. Thus, under the “means-plus-function” perspective, the indefiniteness of “enhancement” may no longer be a problem. Rather, it becomes part of an insufficiently defined act (means) to perform a function in a means-plus-function claim.

Further, courts allow linking of a function by the prosecution history to “inform [] the meaning of the disputed claim phrase and address[] an ambiguity otherwise left unresolved.” Personalized Media Communications, 952 F.3d at 1345. Thus, a patent owner is provided with several opportunities to show that the means-plus-function phrase is supported with structure in the specification and in the prosecution history.

Although a patent owner often wants to avoid unintended invocation of §112(f) because of narrowness concerns, such narrowness and literal equivalents thereof under §112(f) might not be a problem in a pharmaceutical method of use particularly if it avoids an indefiniteness conclusion. Additionally, when there is an allegedly indefinite term in the claim, consider whether one could argue that the term recites a function or insufficiently defined structure or act to invoke a means-plus-function limitation to reduce the possibility of running afoul of §112(b). Remember though, one of ordinary skill in the art must be able to recognize structure in the specification or prosecution history as clearly linked to the means-plus-function element. If not, the claim may still have an indefiniteness issue under §112(b).

† Kathleen Hanley is a Summer Associate at Finnegan.

‡ Stacy Lewis is a Law Clerk at Finnegan.