What is the significance of the Supreme Court decision on "pemetrexed disodium"?

Actavis UK Limited & Ors v Eli Lilly and Co [2017] UKSC 48 concerns Eli Lilly's European patent, EP 1 313 508, claiming a combination of pemetrexed disodium with vitamin B12 for the prevention of the growth of tumours.

Actavis sought declarations that its proposed pemetrexed diacid, pemetrexed dipotassium and pemetrexed ditromethamine products would not infringe this patent.

The focus of the case was on the limitation of the claim language "pemetrexed disodium" – does the scope of the claim nonetheless extend to pemetrexed dipotassium, pemetrexed diacid or pemetrexed ditromethamine? The Patents Court and the Court of Appeal held that these other forms of pemetrexed were not protected by the claim.

Now, in a widely unexpected and important decision, the UK Supreme Court has held that the claim may be infringed by other forms of pemetrexed, including pemetrexed dipotassium and pemetrexed diacid.

The decision makes it clear that the protection of patent claims may extend beyond the scope of their language, in certain circumstances, to include immaterial variants – referred to in many jurisdictions as a "doctrine of equivalents".

The Eli Lilly decision appears far-reaching: a claim to one salt of a compound has been held to protect a salt of that compound that is not claimed. How will the decision impact on other cases?

Undoubtedly, the Supreme Court decision in Eli Lilly will be tested by patentees and third parties in the months and years to come. It will be argued by patentees that the decision now applies to extend claim protection to products or processes in ways that would have earlier been thought far-fetched.

Indeed, the decision appears intended to tip the balance when examining infringement towards protection for patentees and away from certainty for third parties.

As regards third parties, they will naturally have to scrutinise this decision when considering those patents that potentially block launch strategies and other activity, and how they might work-around them.

Furthermore, the Supreme Court has clarified two, narrow circumstances in which the contents of the prosecution file may apply. As a result, more attention will need to be paid to what was said and done in this file when considering claim scope.

There are, however, reasons for reading Eli Lilly circumspectly.

Firstly, despite the result of the decision, the Supreme Court appears to regard it as a clarification of the law, rather than a change of course – "our domestic law has long recognised that an immaterial variant does not get the infringer off the hook" – and Lord Neuberger finds English cases dating back to as early as 1843 in which protection was held to extend to variants that are outside the claim language.

This may allow the first instance courts to take a cautious approach to the application of the decision, wary of “opening the floodgates”.

Secondly, contrary to the norm in English patent cases, there was no validity counterclaim to infringement in Eli Lilly for the Supreme Court to consider. Such validity counterclaims can place an important 'squeeze' on the scope that a patentee contends for its patent claims.

The most obvious such squeeze is the risk that a claim too broadly construed will be found insufficient. The Supreme Court appears to allude to this when it states that the disclosure of the patent should not be confused with its scope of protection.

Thirdly, the Supreme Court draws attention to the significance of the variant to the invention. The court suggests that a variant is more likely to be immaterial if it is not part of the inventive concept claimed.

In the present case, the sodium cation is not part of the inventive concept, which is instead the administration of the pemetrexed anion together with vitamin B12. Not all claim features will be part of the inventive concept as construed in every case.

Therefore, this way of looking at a claim may serve as a broader guide as to whether a variant is likely to fall within the scope of protection or not.

There is a final point to consider. The Supreme Court refers to the fact that it believes the approach to the scope of protection of claims set out in Eli Lilly is consistent with other European courts, particularly Germany and the Netherlands; these jurisdictions have made allowance for many years for certain features to be included within the scope of protection of claims even though they fall outside the language used.

However, in practice, it is fair to say that this is used as something of a last resort in these countries, to avoid an unfair result. If this experience is any guide, decisions in the English courts that a variant that lies outside the language of a claim is nonetheless protected by it, may remain exceptional.