The Supreme Court on Using Prosecution History to Interpret Claims

Charlotte Rush & Avi Freeman | August 2017

We reported recently that the UK Supreme Court has issued a judgment in Eli Lilly v Actavis UK Limited.  The judgment is about the infringement by Actavis of Eli Lilly’s patent claiming an anti-cancer drug containing pemetrexed disodium and vitamin B12. 

Actavis had developed a cancer treatment involving the combination of pemetrexed compounds and vitamin B12.  Though the pemetrexed compounds did not include pemetrexed disodium, the court found that the Actavis products directly infringed the Lilly patent.

Our initial report (Decision of the United Kingdom Supreme Court on Non-Literal Infringement) discussed how this judgment has established new law on the interpretation of claims for infringement issues.

Another notable aspect of this judgment is the discussion of the use of prosecution history, i.e. the record of the exchange between the applicant’s representative and the patent office, to aid claim interpretation.

In UK courts, the use of prosecution history in the interpretation of claims has generally been discouraged.  However, the possibility of using the prosecution history for the Lilly patent in this case had been raised as an issue.

The court handled the question of infringement by initially disregarding prosecution history and coming to the provisional conclusion that the Actavis products indeed infringed the patent.  The court then considered the use of prosecution history and how it would affect the finding of infringement.

Actavis supported the use of the prosecution history because of the view that the proceedings before the European Patent Office made it clear that only the use of pemexetred disodium, and no other pemexetred compound, could lead to infringement of the Lilly patent.

The prosecution history for the Lilly patent shows that the use of the term “pemetrexed disodium” in the claims resulted from objections to broader terms.  Initially, the name of the class of chemicals “antifolate” was used.  However, the examiner objected that there was a lack of disclosure in the specification or this general term. 

The claims were then amended to refer to “pemetrexed,” a specific antifolate, which was objected to for not having basis in the application as filed.  Lilly finally replaced this with the compound “pemetrexed disodium”.

According to Actavis, these actions lead to the interpretation of the claims as being limited to pemetrexed disodium only.  Actavis were of the view that it would be unfair for Lilly to be able to rely on the limitation to pemetrexed disodium during examination, but then argue in infringement proceedings that the scope of their claims actually extends beyond pemetrexed disodium.

Responding to this contention, the court deliberated on the issue of whether, and if so when, it is permissible to turn to the prosecution history of a patent when considering whether a variant infringes.  In dealing with this issue, the court considered the positions taken on the use of prosecution history in the 2004 House of Lords decision of Kirin-Amgen Inc. v Hoechst Marion Roussel Limited, and in other European countries.

In the USA prosecution history is important when it comes to infringement.  Applicants should act with caution in US patent prosecution when it comes to making amendments or arguments that could be interpreted as disclaiming subject-matter.  The US law regarding the effect that such amendment can have on the availability of protection for equivalents is well known.  In the UK it has always been different since courts are generally reluctant to give much weight to the prosecution history.

In this case, the Supreme Court agreed with the comments in the Kirin-Amgen decision which cautioned against the use of prosecution history in claim construction, in line with the approaches of the courts in Germany and the Netherlands (more on Europe below).  It was indicated that “a sceptical, but not absolutist, attitude” should be taken to the use of prosecution history.

In other words, since the contents of the prosecution file are publicly available and unlikely to be extensive, justice may occasionally require reference to the contents of the file.  However, reliance on the prosecution history to determine the scope of a patent must be limited.

The view was taken that the prosecution history should only be used if

(i)            the point at issue is unclear from the specification and claims and can be unambiguously resolved from the prosecution file, or

(ii)           ignoring the contents of the file would be contrary to the public interest.

The court then considered the issue of whether the prosecution history of the patent in this case altered the provisional conclusion of infringement.  It was decided that it did not.

The consideration by the examiner of whether or not the teaching of the specification extended to antifolates other than pemetrexed disodium was said to not have any bearing on the question of whether the doctrine of equivalents allowed pemetrexed salts other than pemetrexed disodium to be within the scope of the patent.

This judgment appears to have reinforced the approach taken previously by the House of Lords in Kirin-Amgen, and so the law in this area has not significantly changed.  The Supreme Court has, however, provided further and more precise guidelines on when the prosecution history can or should be used.  Only time will tell whether this will result in a stricter approach, or open the door to a systematic use of prosecution history in certain circumstances.

This is not a radical conclusion to the prosecution history side of the Supreme Court judgment, though a revolution in the use of prosecution history was perhaps not to be expected in the face of such a ground-breaking position on equivalents in infringement.  One drastic change per judgment of the Supreme Court is surely enough.

Beyond the UK

After concluding under UK law that the Actavis products directly infringed the Lilly patent, the Supreme Court then turned to the question of direct infringement in France, Italy and Spain.  It is a feature of European patent law that a court in one European state can make a judgment with respect to infringement of corresponding designations in other EPC states.

The Supreme Court decided that under French law, the doctrine of equivalents applied in this case, which was contrary to the position taken by the Court of Appeal.  Under Italian law, the Supreme Court again rejected the Court of Appeal’s conclusion, and decided that it was clearly appropriate to apply the doctrine of equivalents. 

When addressing the question under Spanish law, it was held that the Spanish courts would maintain their previous procedure of following the UK approach by adopting the Supreme Court’s recasting of the Improver questions.  This decision was reached partly because it would bring the Spanish courts more in line with the German and Dutch courts.

By this reasoning, the Supreme Court also concluded that direct infringement would be established in France, Italy and Spain.

Irrespective of what one might think about the merits of the judgment itself and its conclusions regarding direct infringement, from the perspective of providing certainty to businesses it is reassuring that the same result has been reached in each of these different European jurisdictions.