Federal Circuit Emphasizes the Importance of Prosecution History in Resolving Ambiguous Claim Terms in University of Massachusetts v. L’Oréal USA, Inc.

Authored by Richard Kurz and Anne Bolton

On June 13, 2022, the Federal Circuit issued a precedential opinion that vacated the district court’s judgment of indefiniteness, deciding that the ruling was based on an erroneous claim construction.1  The patents-in-suit claimed methods for skin enhancement by topical application of compositions containing adenosine.2  The independent claims contain two clauses that recite an adenosine concentration range.3  The first clause refers to “topically applying to the skin a composition comprising adenosine.”4  The second clause recites a range of “adenosine concentration applied to the dermal cells,” which are cells that are located below the skin surface (the skin surface is the epidermis).5  This made the claim language ambiguous about whether the claimed concentration range is the adenosine concentration in the composition itself, or is instead the concentration that is suffused into the subsurface dermal cells.6  The district court determined that the plain and ordinary meaning of the claim language is that the recited range is the adenosine concentration in the dermal cells, rather than the concentration in the composition.7  Noting the distinction between the two clauses, both of which referred to concentration, the district court held that the claims were indefinite because they were ambiguous and entered a final judgment of invalidity.8

On appeal, the Federal Circuit Panel determined that the claim language was ambiguous, but explained that the district court should have looked to the specification and prosecution history to attempt to resolve the ambiguity before making an indefiniteness determination.9  Despite the ambiguous claim language, the Federal Circuit determined that the specification and prosecution demonstrated that the claim would be understood as referring to the adenosine concentration in the composition.10  Thus, the Federal Circuit vacated the district court’s indefiniteness ruling and remanded the case to the district court to proceed under the new claim construction.11


The University of Massachusetts and its exclusive licensee, Carmel Laboratories, LLC, (collectively, “UMass”), filed an infringement action in 2017 in the District of Delaware against L’Oréal S.A. and its American subsidiary, L’Oréal USA, Inc. (“L’Oréal”).12  The action concerned patents claiming a method to enhance skin without increasing dermal cell growth by applying a topical composition containing a stated concentration of adenosine.13  The patent specifications describe human skin as having two primary layers:  the epidermis, which is the surface layer, and the dermis, which is the deeper layer containing dermal cells.14  The independent claims contain two clauses that made the claims ambiguous.15  The “skin enhancing clause” recites “topically applying to the skin a composition comprising a concentration of adenosine.”16  The claims then end with a “wherein clause” that recites “wherein the adenosine concentration applied to the dermal cells is 10-4 M to 10-7 M.”17  The issue on appeal was whether the recited range refers to the concentration of the product applied to the skin, as L’Oréal contended, or the concentration suffused into the dermal cells after application, as UMass argued.18

Relevant to the decision was that in March 2018, L’Oréal filed petitions for inter partes review of the two patents, which the Patent Trial and Appeal Board (“PTAB”) denied.19  In denying the petition, the PTAB adopted UMass’s construction that the wherein clause recites the adenosine concentration in the subsurface dermal cells.20

The district court agreed with the PTAB’s construction, determining that the wherein clause “has its plain and ordinary meaning without the need for further construction.”21  Emphasizing the distinction between the concentration recited in the wherein clause and the skin enhancement clause, the district court granted L’Oréal’s motion for summary judgment of invalidity on grounds of indefiniteness.22

The Federal Circuit’s Analysis

On appeal, the claim construction was reviewed de novo.23  The Panel explained that words of a claim are generally given their plain and ordinary meaning, but this must be viewed in context of the specification and the prosecution history, especially when resolving ambiguities.24

The Panel started its analysis with the claim language, and concluded that in context of the claim as a whole the language was not plain on its face.25  The Panel first noted that the word “apply” refers to the skin in one clause and to the dermis in the other, but decided that “this does not mean that different things are being applied.”26  Rather, the same concentration “can be applied directly to one object and indirectly to another.”27  Next, the Panel explained that the wherein clause contains the phrase “the adenosine concentration,” suggesting an antecedent connection to the preceding clause’s reference to “a concentration of adenosine.”28  Lastly, the Panel reasoned that under UMass’s construction requiring that the concentration be measured in the dermal cells, the claim would then refer to a concentration that does not exist before the composition is applied.  If so, the Panel concluded that such an interpretation would therefore require the wherein clause to be rewritten to clarify that concentration is measured after application and suffusion.29

The Panel next looked to the specification and noted that none of the embodiments described as “the invention” specify a concentration measurement “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.”30  UMass argued that the specification discusses experiments that directly exposed dermal cells to the recited adenosine concentrations in a laboratory, but this did not persuade the Panel that the invention would include “measuring concentrations beneath the skin surface after topical application.”31

Lastly, the Panel determined that the prosecution histories provided the strongest evidence to resolve the ambiguity concerning the wherein clause.32  A predecessor of the independent claim, which was later amended to the language in the patents’ claims, lacked the wherein clause but contained a separate dependent claim that included the concentration range but made no mention of the dermal cells.33  To overcome a prior art rejection, the applicants added the wherein clause into the independent claim and at that point added the “applied to the dermal cells” language.34  Notably, in the office action response, the applicants described the amended language to the examiner and implied that adding “dermal cells” to the clause changed nothing about where the concentration was to be measured.35

The Panel ultimately decided that although the claim language appeared ambiguous on its face, the specification and, more significantly, the prosecution history demonstrated that the claim referred to the adenosine concentration in the composition.36  As the Panel explained, “[b]ecause the meaning of the relevant claim language is not plain, but rather ambiguous,” the court “can look to the prosecution history to ‘inform the meaning of the disputed claim phrase and address an ambiguity otherwise left unresolved.’”37  Thus, the Panel “[held] that this prosecution history requires that the wherein clause’s reference to the recited concentrations being ‘applied to the dermal cells’ be read as referring to concentrations of the composition applied to the skin’s surface.”38

The Decision’s Impact and Takeaway

The Panel’s decision and reasoning demonstrates that ambiguous claim language should be resolved, to the extent possible, based on the intrinsic record before concluding that a claim is indefinite.39  In this case, the Panel looked beyond plain and ordinary meaning of the terms in the claim, and evaluated the specification and prosecution history to resolve the ambiguity.40  Thus, a takeaway from the Panel’s opinion is that claim terms that are otherwise ambiguous may be construed in a way that resolves the ambiguity based on the intrinsic record.

1 Univ. of Mass. v. L’Oréal S.A., No. 2021-1969, slip op. at 1 (Fed. Cir. June 13, 2022).
2 Id.
3 Id. at 3.
4 Id. at 8.
5 Id.
6 Id. at 5.
7 Id.
8 Id. at 6.
9 Id. at 8.
10 Id. at 14.
11 Id. at 7.
12 Id. at 2. The district court granted L’Oréal S.A.’s motion to dismiss for lack of personal jurisdiction. This decision was vacated on appeal and the Federal Circuit ruled that UMass was entitled to conduct jurisdictional discovery. Id. at 3.
13 Id. at 3.
14 Id.
15 Id. at 8.
16 Id.
17 Id.
18 Id. at 6.
19 Id. at 4.
20 Id.
21 Id. at 5.
22 Id. at 6.
23 Id. at 7.
24 Id.
25 Id. at 8.
26 Id. at 8-9.
27 Id. at 9.
28 Id.
29 Id. at 10.
30 Id. at 11.
31 Id. at 12.
32 Id.
33 Id. at 13.
34 Id.
35 Id.
36 Id. at 8.
37 Id. at 14 (quoting Personalized Media Commc’ns, LLC v. Apple Inc., 952 F.3d 1336, 1345 (Fed. Cir. 2020)).
38 Id.
39 Id. at 7.
40 Id.