When the description limits the scope of the invention: careful drafting really matters!

Author: Stefano Barazza (Studio Legale Barazza)

AstraZeneca AB and others v Hanmi USA Inc and others, United States Court of Appeals for the Federal Circuit, Docket No 2013-1490, 19 December 2013

Journal of Intellectual Property Law & Practice (2014) doi: 10.1093/jiplp/jpu054, first published online: April 18, 2014

The Federal Circuit found that a written description defining ‘the present invention’ as a limited subset of the substance mentioned in the claims clearly confined the invention to the limited subset, disclaiming anything else. The doctrine of claim differentiation cannot override the limitations unmistakably set out by the patent applicant in the written description.

Legal context and facts

In 1995, AstraZeneca filed a patent application covering pharmaceutical compositions containing certain salts of an omeprazole enantiomer, namely those defined by the cations Na+, Mg2+, Li+, K+, Ca2+ or N+(R)4. The invention also claimed methods of use of such compositions for the treatment of gastric acid related diseases, including gastrointestinal inflammatory diseases. In response to the rejection of the original claims, AstraZeneca amended its application, focusing on the S-enantiomer of omeprazole, esomeprazole. The amended claims covered pharmaceutical compositions comprising esomeprazole and an ‘alkaline salt’ (US Patent No 5,714,504) or a ‘pharmaceutically acceptable salt’ (US Patent No 5,877,192).

The pharmaceutical company soon brought the invention to the market, manufacturing the brand drug Nexium, containing the magnesium salt of esomeprazole as its active ingredient, for the treatment of gastroesophageal reflux disease and other gastric acid related diseases. In 2010, Hanmi filed a New Drug Application with the US Food and Drug Administration, seeking regulatory approval for a drug containing the strontium (Sr2+) salt of esomeprazole. Hanmi certified, under 21 USC s 355(b)(2)(A)(iv), that AstraZeneca's '504 and '192 patents were invalid or would not have been infringed by the new product.

AstraZeneca filed suit against Hanmi before the District Court for the District of New Jersey (Civil Action No 11-760 JAP), alleging patent infringement under 35 USC s 271(e)(2)(A). In December 2012, the district court ruled on the parties' request for claim construction, finding that the term ‘alkaline salts’, contained in the claims of the '504 patent, was defined by the related written description as encompassing only the Na+, Mg2+, Li+, K+, Ca2+ or N+(R)4 salts. The same construction was applied to the term ‘pharmaceutically acceptable salts’, employed in the '192 patent, which incorporated by reference the description contained in the '504 patent. The parties consented to the entry of a final judgment that, under the district court's claim construction, Hanmi's product did not infringe the asserted patents. AstraZeneca brought an appeal before the Court of Appeals for the Federal Circuit, challenging the district court's construction of the term ‘alkaline salts’ in the '504 patent.


The Federal Circuit upheld the district court's decision, finding that the written description of the '504 patent contained a clear disclaimer of any salt except those characterized by the six enumerated cations. In reaching this conclusion, the court primarily relied on the detailed description included in the '504 patent, according to which:
The present invention refers to the new Na+, Mg2+, Li+, K+, Ca2+ or N+(R)4 salts of the single enantiomers of omeprazole, where R is an alkyl with 1–4 carbon atoms, i.e. Na+, Mg2+, Li+, K+, Ca2+ or N+(R)4 salts of (+)-[omeprazole] and (–)-[omeprazole], where R is an alkyl with 1–4 carbon atoms.
The judges held that, by using the term ‘the present invention’, AstraZeneca provided a clear definition of the scope of its invention, limiting it to the six identified salts. Further, they noted that the abstract confirmed this limiting disclaimer, as the inventor only mentioned ‘the [n]ovel optically pure compounds’ formed by the above-mentioned cations. Reciting previous case law (Verizon Services Corp v Vonage Holdings Corp, 503 F 3d 1295 [2007]; Honeywell International Inc and others v ITT Industries Inc and others, 452 F 3d 1312 [2006]; and SciMed Life Systems Inc v Advanced Cardiovascular Systems Inc. 242 F 3d 1337 [2001]), they concluded that those statements clearly confined the invention to the six identified cations. The panel clarified that AstraZeneca, by using such language and conspicuously choosing only certain members of the class of salts potentially suitable for use in the invention (which included all the metals of Periodic Table Groups IA and IIA, plus ammonium), ‘conveyed a clear and definitive meaning that it was disclaiming other members of the class—like Hanmi's chosen strontium’.

The court also reviewed and dismissed three arguments advanced by the appellant to dispute the district court's claim construction.

With a first claim, AstraZeneca argued that the six identified salts were just examples of the broader group of ‘alkaline salts’ claimed by the invention. This interpretation, according to the pharmaceutical company, was justified by the presence of a sentence, in the written description of the '504 patent, according to which the ‘[a]lkaline salts … are, as mentioned above, besides the sodium salts … and the magnesium salts …, exemplified by their salts with Li+, K+, Ca2+ or N+(R)4’.

The panel found that the statement did not negate the clear disclaimer language employed in the written description and in the abstract. In this perspective, the judges noted that only four of the six cations were directly mentioned as examples, and that the sentence constituted a mere summary of the two preceding paragraphs, respectively dedicated to the salts from Group IA of the Periodic Table, including sodium (Na), and to those from Group IIA, including magnesium (Mg).

The second argument raised by the appellant concerned the amendments introduced in the patent application after the examiner's rejection of the original claims. AstraZeneca alleged that a broad interpretation of ‘alkaline salts’ was supported, in the prosecution history, by the clinical studies submitted when it amended the original claims to focus on esomeprazole. These studies allegedly ‘involved both the monovalent sodium salt and the divalent magnesium salt of [esomeprazole], thus supporting the full scope of the genus of alkaline salts disclosed in the application and as claimed herein’.

The court again dismissed the argument, finding that the sentence mentioned by the appellant, read in the context of an amendment that narrowed the rejected claims and of the clear limitation set forth in the written description, did not support AstraZeneca's conclusion. Reciting previous case law (Eli Lilly & Co v Teva Parenteral Medics Inc, 689 F 3d 1368 [2012]; Merck & Co v Mylan Pharmaceuticals Inc, 190 F 3d 1335 [1999]), it clarified that ‘the term “genus” can refer simply to an enumerated collection, without an independently unifying characteristic of the collection's members – as when “genus” is used for a Markush-type claim that recites a group whose members may have nothing in common but their membership in the group’. The judges applied this teaching to the sentence at issue, concluding that the reference to the salts ‘disclosed in the application and as claimed herein’ limited the genus to the six identified salts. The panel also observed that the prosecution history did not mention, nor included data for, any salt beyond those identified in the written description.

Finally, the court evaluated AstraZeneca's argument on the applicability of the doctrine of claim differentiation. The appellant noted that each independent claim reciting a pharmaceutical composition comprising an ‘alkaline salt’ had a dependent claim that differed only by the addition of ‘wherein the alkaline salt is a Na+, Mg2+, Li+, K+, Ca2+ or N+(R)4 salt’. Thus, AstraZeneca claimed that the doctrine of claim differentiation prevented an interpretation that limited the definition of the term ‘alkaline salts’ used in the independent claims to the limited subset mentioned in the dependent claims, as such interpretation would have rendered the latter claims redundant, being identical in scope to the former. The judges, however, swiftly dismissed this argument, noting that the doctrine of claim differentiation ‘cannot override the unmistakable limitation of “alkaline salts” set out in the written description’, as clear statements of scope in the specification prevail on the inference otherwise suggested by claim differentiation (The Toro Co v White Consol Indus Inc, 199 F 3d 1295 [1999]).

Practical significance

The decision of the Federal Circuit falls in line with the previous case law that examined the relevance of the specification during the phase of claim construction. It has clarified that the claims should be read in light of the specification (see Slimfold Mfg Co v Kinkead Indus Inc, 810 F 2d 1113 [1987]: ‘[c]laims are not interpreted in a vacuum, but are part of and are read in light of the specification’), without unnecessarily importing limitations from it. However, the ‘[i]nterpretation of descriptive statements in a patent's written description is a difficult task, as an inherent tension exists as to whether a statement is a clear lexicographic definition or a description of a preferred embodiment’ (E-Pass Technologies Inc v 3Com Corp, 343 F 3d 1364 [2003]). The interpreter, therefore, should look for a ‘clear disclaimer’, through which the patentee explicitly limited the scope of the claims (Liebel-Flarsheim Co and others v Medrad Inc, 358 F 3d 898 [2004]), even if it did not employ an explicit definitional language (Phonometrics Inc v Northern Telecom Inc, 133 F 3d 1459[1998]).

In the case in hand, the court identified the ‘clear disclaimer’ in the statements found in the detailed description and in the abstract, which respectively referred to the six identified salts when describing the ‘present invention’ and the ‘novel compounds’. In SciMed Life Systems Inc v Advanced Cardiovascular Systems Inc, the Federal Circuit relied on similar statements to infer ‘a clear case of disclaimer of subject matter that, absent the disclaimer, could have been considered to fall within the scope of the claim language’ (similarly, see Honeywell International Inc, 452 F 3d 1312 [2006]). In particular, the use of the words ‘the present invention’, ‘this invention’ or ‘all embodiments of the present invention’ is particularly effective in conveying the idea that the patentee is describing the invention as a whole, rather than one of its embodiments. Incidentally, when the specification employs such language, courts are not generally required to evaluate whether the patentee intended, instead, to describe a specific embodiment: according to Modine Manufacturing Co v United States ITC (75 F 3d 1545 [1996]) ‘when the preferred embodiment is described as the invention itself, the claims are not entitled to a broader scope than that embodiment’.

A clear disclaimer language, as shown in the present decision, cannot be easily overcome. The court clarified that sporadic ambiguous statements contained in the specification, or submitted during prosecution, are insufficient to this aim. In Honeywell International Inc, the Federal Circuit exhibited the same attitude towards the relevancy of prosecution history, noting that ‘[w]here … the written description clearly identifies what his invention is, an expression by a patentee during prosecution that he intends his claims to cover more than what his specification discloses is entitled to little weight’ (citing Biogen Inc v Berlex Labs, 318 F 3d 1132 [2003]). Similarly, the doctrine of claim differentiation, according to the court, cannot override the clear disclaimer language used by the patentee (see Multiform Desiccants Inc v Medzam Ltd, 133 F 3d 1473 [1998]: ‘the doctrine of claim differentiation can not broaden claims beyond their correct scope, determined in light of the specification and the prosecution history and any relevant extrinsic evidence’).

In light of the guidance provided by the Federal Circuit, patent applicants should ensure that the specification supports the breadth of the claims, without containing any language that could be interpreted as a clear disclaimer. In particular, the specification should unambiguously distinguish the statements that describe the invention as a whole from those which concern one or more of its embodiments, employing a coherent language throughout the application.

1 comment:

  1. Usually towards the end of examination at the EPO the description is amended to bring it into conformity with the claims that have been allowed. In my experience this doesn't happen before the USPTO. However perhaps it is something that should be given consideration in view of this decision.