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UK Court Expands File-Wrapper Estoppel, but not Doctrine of Equivalents

The decision in the case of Actavis v Eli Lilly was handed down by the High Court on 15 May 2014. This rather lengthy decision by Mr Justice Arnold touches on a multitude of issues.  Of particular interest, are:

  • Divergence (not for the first time) between the UK and German courts over the so-called Doctrine of Equivalents
  • A revival of the Improver questions for considering whether a “variant” falls within the scope of a claim
  • More “file-wrapper estoppel” and
  • A new-found confidence in the UK Court in granting an order (declaration of non-infringement) with extra-territorial reach.

Outline of the case

Actavis was seeking a declaration of non-infringement of Eli Lilly patent EP1313508. This patent relates to the use of pemetrexed disodium in combination with vitamin B12 or a pharmaceutical derivative thereof and optionally a folic acid.  Eli Lilly have marketed this product as Alimta and it has been used in chemotherapy for the treatment for certain types of lung cancer since 2004.  Actavis wish to bring to market a combination of pemetrexed diacid, pemetrexed dipotassium or pemetrexed ditromethamine with vitamin B12 and a folic acid and intend to obtain regulatory approval for their product by reference to Alimta.

A key issue of the case revolved around whether the term “pemetrexed disodium” could be interpreted to provide a scope of protection covering all compositions containing pemetrexed.

Differences between UK and German cases

Contrary to the decision of the English High Court, the decision of the German Düsseldorf Regional Court held that the use of pemetrexed dispotassium would infringe claim 1 of the German designation of the Eli Lilly patent.  In arriving at this decision, it was found that, while there was no infringement of the patent if the claims were construed literally, there was infringement of the patent if the claims were construed using the doctrine of equivalents, i.e. while two features may not be exactly the same, they are close enough to be considered equivalents that are both protected by the scope of a claim. Importantly, Mr Justice Arnold disagreed with the approach of the German court constructions of the claims and the lack of consideration given to the prosecution history of the patent.

Claim construction to determine infringement, and the use of patent prosecution history as a guide

Under UK law, as well as that of the EPO and many other territories, it is important to properly identify the “person skilled in the art” when attempting to construe the claims of a patent and determine their scope of protection.  A substantial part of the decision relates to settling this issue and the disagreements between the parties as to the identity of the skilled person (or in fact the team of skilled persons) and what formed the common general knowledge.  The correct interpretation of the person skilled in the art is of great importance when determining infringement, and it is unwise for an inventor or lay person to interpret claims.  Rather, it is a point to be carefully considered with a patent attorney whose role it is to anticipate how the courts approach this aspect of patent law.

Mr Justice Arnold went on to provide a thorough analysis of the UK approach to claim construction.  The basis for how to interpret claims is set out for all of the countries in which Actavis sought a declaration of non-infringement by the protocol on the implementation of Article 69 of the European Patent Convention (EPC).  This protocol has been integrated into the national law of all member states which are party to the EPC.  Article 2 of the protocol states that “for the purposes of determining the extent of protection conferred by the European patent, due account shall be taken of any element which is equivalent to an element specified in the claims”.  When considering

  • whether pemetrexed disodium is equivalent to
  • pemetrexed dipotassium, pemetrexed diacid, or pemetrexed ditromethamine,

the court applied the Improver Questions.  These questions were developed in the case of Improver Corp v Remington Consumer Products Ltd [1990] FSR and set out the principles of assessing if a feature of a claim is equivalent to that of a potentially infringing article.

The Improver questions are as follows:

  1. Does the variant have a material effect upon the way the invention works?  If yes, the variant is outside the claim.  If no -
  2. Would this (i.e. that the variant had no material effect) have been obvious at the date of publication of the patent to a reader skilled in the art?  If no, the variant is outside the claim. If yes -
  3. Would the reader skilled in the art nevertheless have understood from the language of the claim that the patentee intended that strict compliance with the primary meaning was an essential requirement of the invention?  If yes, the variant is outside the claim.

File Wrapper Estoppel

Mr Justice Arnold also turned to the prosecution history of the Eli Lilly patent when considering the answers to the Improver Questions.  UK courts have been hesitant to take the prosecution history of a patent into consideration when assessing claim construction. However, in this instance, Arnold J. held that it was appropriate, as Eli Lilly had narrowed their original claim from “an antifolate” to “pemeterex disodium”.  In the decision, Arnold J. supported this approach by stating:

“I accept that, for the reasons explained by Jacob J in Bristol-Myers Squibb and Lord Hoffmann in Kirin-Amgen, courts should be cautious before relying upon prosecution history as an aid to construction. In the real world, however, anyone who is interested in ascertaining the scope of a patent and who is professionally advised will obtain a copy of the prosecution file (most, if not all, of which is generally open to public inspection) and will consider it to see if it sheds light on the matter.  In some cases, perhaps not very many, the prosecution history is short, simple and shows clearly why the claims are expressed in the manner in which they are to be found in the granted patent and not in some broader manner.  In such a situation, there is no good reason why the court should shut its eyes to the story told by the prosecution file.  On the contrary, consideration of the prosecution file may assist in ensuring that patentees do not abuse the system by accepting narrow claims during prosecution and then arguing for a broad construction of those claims for the purpose of infringement. 

It was on the basis of this assessment of the claims that Arnold J. decided that Actavis did not infringe the Eli Lilly patent and were entitled to a declaration of non-infringement in the UK, France, Italy, and Spain.

Declaration of non-infringement for foreign territories

Actavis sought a declaration for non-infringement not just for the UK designation of the Eli Lilly patent but also for France, Italy, and Spain.  Eli Lilly argued that the relevant law applicable to each of the patents in these countries was the national law of those countries. Mr Justice Arnold had to consider whether the court was able to issue a declaration of non-infringement for the foreign territories.  Unusually for a UK court, he held that the applicable law was indeed English law and that it was proper for the court to issue a declaration of non-infringement in France, Italy, and Spain as well as in the UK. 



The doctrine of preventing abuse of the system by accepting narrow claims during prosecution and then later arguing for broader claims is referred in the US as “file wrapper estoppel” and is contrary to UK tradition that the patent, like a contract, is to be interpreted without reference to extraneous evidence.  This is not the first decision to depart from that  tradition - see Rohm & Haas v. Collag in Autumn 2002 edition of this newsletter and Monsanto v Cargill in our Spring 2006 edition, but this new decision is more unequivocal.  It does not merely put a foot in the door of file wrapper estoppel.  It kicks the door down. 

It should be no great surprise that the UK Court takes a view that when a patentee writes “sodium” in a claim, he or she does not mean “potassium”, and the need for third party certainty set out in the Protocol of Interpretation of Article 69 should not extend the scope of a claim in such a way.   The “Improver Questions” may have been out of favour in the last ten years, but whether they are used as a tool for interpreting “variants” or some other approach is used, UK courts are consistently against ignoring or re-writing explicit terms in a claim – see House of Lords Rules out Doctrine of Equivalents in the Autumn 2004 edition of this newsletter.

This decision may pave the way to more UK court judgements extending to other European states where the same patent claims are in force.  It may increase the popularity of the UK courts as a venue for seeking declarations of non-infringement.