The return of the doctrine of equivalents


Geoff Hussey and Varuni Paranavitane

The return of the doctrine of equivalents

yuriyzhuravov /

In a very significant decision, the UK Supreme Court has changed the test for patent infringement, reintroducing a doctrine of equivalents across much of Europe. Geoff Hussey and Varuni Paranavitane of AA Thornton report.

In or around 2000, Eli Lilly discovered that pemetrexed—an antifolate, which was known to have therapeutic effects on cancerous tumours but which was also known to have seriously damaging side-effects—could be safely administered if done so together with vitamin B12.

Eli Lilly applied for a European patent (EP1313508) covering the use of any antifolate. During prosecution Eli Lilly initially narrowed the claims to pemetrexed and then to pemetrexed disodium so that the European Patent Office would grant the patent. Eli Lilly has successfully marketed the drug since 2004 as Alimta.

In 2012, Actavis sought declarations of non-infringement at the English High Court in respect of many European designations of the patent for use of (a) pemetrexed diacid, (b) pemetrexed ditromethamine, and (c) pemetrexed dipotassium.

The High Court found there to be no infringement, whereas the Court of Appeal held that although the Actavis products did not directly infringe, they did so indirectly due to the presence of sodium ions in the solution used to administer the drug.

In July, the UK Supreme Court overturned these decisions and held that the use of pemetrexed diacid, ditromethamine and dipotassium directly infringes the UK, French, Spanish and Italian patents that specify use of pemetrexed disodium. In doing so the Supreme Court has not only significantly changed the test for patent infringement, clearly introducing a doctrine of equivalents, but it has also reduced the ultimate effect of certain types of claim amendments made during prosecution.

The new infringement test

Lord Neuberger, giving the judgment of the Supreme Court, outlined how the question of patent infringement should be approached by addressing two issues through the eyes of the skilled addressee of the patent.

(i) Does the variant infringe any of the claims as a matter of normal interpretation; and, if not,

(ii) Does the variant nonetheless infringe because it varies from the invention in a way or ways which is or are immaterial?

Lord Neuberger considered that issue (i) raised a pure question of interpretation; whereas issue (ii) raised a question which would normally be answered by reference to the facts and expert evidence.

In relation to issue (ii) Lord Neuberger held that the following three questions should be used for guidance on whether a variant should fall within the scope of protection of a patent.

Notwithstanding that it is not within the literal meaning of the relevant claim(s) of the patent, does the variant achieve substantially the same result in substantially the same way as the invention, ie, the inventive concept revealed by the patent?

Would it be obvious to the person skilled in the art, reading the patent at the priority date, but knowing that the variant achieves substantially the same result as the invention, that it does so in substantially the same way as the invention?

Would such a reader of the patent have concluded that the patentee nonetheless intended that strict compliance with the literal meaning of the relevant claim(s) of the patent was an essential requirement of the invention?

In reaching this approach Lord Neuberger considered article 69(1) of the European Patent Convention (EPC) 2000, which sets out the basic approach that the extent of protection conferred by a European patent shall be determined by the claims, but that the description and drawings shall be used to interpret those claims.

He also paid close attention to the Protocol on the Interpretation of Article 69 and its attempt to strike a balance between a fair protection for the patentee and a reasonable degree of legal certainty for third parties. Article 2 of the protocol states that due account shall be taken of any element which is equivalent to an element specified in the claims.

As for the UK, this new test provides a significant departure from well-established principles that have been applied for many years. Lord Neuberger was well aware of this and provided a thorough examination of the previous approach, starting with Catnic Components v Hill & Smith, in 1982. Here, Lord Diplock approved a test aimed at establishing whether the skilled addressee of the patent would understand that strict compliance with the claim was intended to be an essential requirement of the invention, so that any variant would fall outside the monopoly claimed even though it could have no material effect upon the way the invention worked.

This approach was developed in 1990 by Mr Justice Hoffman in Improver v Remington when the first set of infringement questions (the so-called Improver questions) were used: first, does the variant have a material effect upon the way the invention works?; second, would the fact that the variant had no material effect have been obvious at the date of publication of the patent?; and third, 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?

Lord Hoffman (as he was by then) went on to say, in Kirin-Amgen v Hoechst Marion Roussel in 2005 that rather than adhering to literalism and adopting a doctrine of equivalents, the solution was “to adopt a principle of construction which actually gave effect to what the person skilled in the art would have understood the patentee to be claiming”. He also said that article 69 “firmly shuts the door on any doctrine which extends protection outside the claims”.

The approach across Europe

The Supreme Court had to decide the issue under UK, French, Italian and Spanish law. As part of his analysis Lord Neuberger considered the approach to infringement traditionally taken by courts in these countries as well as in Germany and the Netherlands. The resulting judgment contained a succinct analysis of the law of infringement across Europe.

Perhaps as a result of its jurisdiction over the French, Italian and Spanish patents in this case, the Supreme Court appears to have been keen to harmonise the law on infringement across Europe. In its analysis it has attempted to ensure that the same result would be achieved in each country. This desire to harmonise is to be welcomed.

The effect of this new test

The main development of the law may reside in the second question of the new test, which includes a new element taking into account that the variant does, and is known to, achieve the same result as the invention. This, the Supreme Court said, can specifically take into account developments that have occurred since the priority date of the invention.

Lord Neuberger said that this was a “pragmatic” approach, but it is a significant departure from the strict principles of analysis as at the priority date that have previously been applied, and formally introduces an element of hindsight into patent law. Previously, courts have tried to eliminate this. Lord Neuberger specifically stated that, when one is considering a variant which would have been obvious at the date of infringement rather than at the priority date, it is necessary to imbue the skilled addressee with rather more information than it might have had at the priority date.

Applying the above new questions to Actavis’s products, the Supreme Court held that they directly infringed Eli Lilly’s patent, and regarded the Court of Appeal as taking an approach which placed too much weight on the words of the claim and not enough on the protocol.

Impact on patent prosecution

In evaluating the scope of protection afforded by a patent, Lord Neuberger referred to Hoffman’s point in Kirin-Amgen that UK courts “discourage, if they do not actually prohibit, use of the patent office file in aid of construction”.

Lord Neuberger has now said that a sceptical but not absolutist attitude should be adopted to the idea that the contents of the prosecution file of a patent should be referred to when considering a question of infringement, in line with the Dutch and German courts. He held that reference to the file would be appropriate only where (i) the point at issue is truly unclear if one confines oneself to the specification and claims of the patent, and the contents of the file unambiguously resolve the point; or (ii) it would be contrary to the public interest for the contents to be ignored.

However, Lord Neuberger held that, despite the claim being specifically limited to the disodium salt in prosecution, there was nothing on the prosecution file that would alter the decision that the diacid, ditromethamine and dipotassium infringed.

The effect of this analysis is that in certain circumstances there may be no lack of protection caused by some claim limitations made during prosecution, particularly if they are done for purposes other than preserving novelty or inventive step.


Since 2005, UK patent practitioners have treated Lord Hoffman’s speech in Kirin-Amgen as the settled law on infringement. This new decision of the Supreme Court has effectively re-introduced a doctrine of equivalents to the UK, with the aim of reaching a consistent approach to the interpretation of the scope of patent protection across Europe. It may have achieved that by clarifying how the Protocol on the Interpretation of Article 69 EPC 2000 should be applied.

This reformed approach to infringement will broaden the scope of protection afforded to patents in certain circumstances but will add complexity to infringement analysis and may reduce certainty for third parties attempting to work around an invention.

Despite this decision stating that the contents of the file history did not alter the infringement decision, it is clear that the file history was considered. Therefore, although some applicants may be more willing to make concessionary amendments when faced with formal objections, patent attorneys should be careful to avoid limiting statements when submitting claim amendments to maximise the chances of obtaining rights that extend beyond the literal wording of the claims. It is now possible for the scope of protection to extend to equivalents.

Geoff Hussey, Varuni Paranavitane, AA Thornton, patent, patent infringement, therapeutic effects, cancerous tumours, Eli Lilly, decision, held, approach