Claim interpretation is a key issue in any patent infringement case. A product or process will only infringe a patent if it contains all the features of at least one claim in the patent. So the question of how to interpret patent claims is of critical importance.
For years, the UK courts have grappled with determining how far the scope of patent protection can extend beyond a patent claim’s literal meaning. The Supreme Court set out a new test in Actavis UK v Eli Lilly  UKSC 48 (12 July 2017). Products which vary only in immaterial ways from the claims of a patent (often described as “variants” or “equivalents”) are now more likely to be found to infringe.
This complex decision may have a significant effect on future UK patent infringement cases. This article summarises the key principles.
Legal background: variants/equivalents
In every jurisdiction, the courts have to set rules for interpreting patent claims. A patent comprises a detailed description of the invention, and, at the end of the description, the claims of the patent. The patent claims set out the scope of the monopoly of the patent holder. In assessing patent infringement, the court must compare the alleged infringement with the language of the claims. The alleged infringement will infringe the patent if it is found to have each “integer” of a claim, i.e. each feature of a claim. Thus, for example, if one integer of a claim states that a particular component of the product must be “curved”, the court must consider the allegedly infringing product and determine whether the component in it is “curved”.
The difficulty is that, depending on the wording of the claim, it may be easy for an alleged infringer to create a product which reproduces all of the key elements of the invention covered by the patent claims, but has a variation to one or more integers which takes it outside the scope of the literal meaning of the claims. Such a product may essentially copy everything which is inventive in the patent, but because of the minor variation, it falls outside the scope of the claim and so does not infringe the patent.
The key question for each jurisdiction is whether a product, which varies in a minor way from the claim of the patent, should be held to infringe the patent, even if this results in the scope of protection of the claims extending beyond their literal meaning.
The US approach: doctrine of equivalents
In the US, the approach taken is the “doctrine of equivalents”. The US approach was summarised by the House of Lords in the seminal case of Kirin-Amgen  UKHL 46, as follows:
“37. In the United States, where a similar principle is called the 'doctrine of equivalents', it is frankly acknowledged that it allows the patentee to extend his monopoly beyond the claims. In the leading case of Graver Tank & Manufacturing Co Inc v Linde Air Products Co 339 US 605, 607 (1950), Jackson J said that the American courts had recognised: 'that to permit imitation of a patented invention which does not copy every literal detail would be to convert the protection of the patent grant into a hollow and useless thing. Such a limitation would leave room for – indeed encourage – the unscrupulous copyist to make unimportant and insubstantial changes and substitutions in the patent which, though adding nothing, would be enough to take the copied matter outside the claim, and hence outside the reach of law'...
“39. However, once the monopoly had been allowed to escape from the terms of the claims, it is not easy to know where its limits should be drawn. In Warner-Jenkinson Co v Hilton Davis Chemical Co 520 US 17, 28-29 (1997) the United States Supreme Court expressed some anxiety that the doctrine of equivalents had 'taken on a life of its own, unbounded by the patent claims'. It seems to me, however, that once the doctrine is allowed to go beyond the claims, a life of its own is exactly what it is bound to have.”
The UK approach
Section 125(1) of the Patents Act 1977, which applies to UK patents, states that the invention in a patent is that set out in the claims, as interpreted by the description and drawings.
Article 69 of the European Patent Convention (“EPC”), which applies to European patents, including those designating the UK, is similarly worded. The Protocol on the Interpretation of Article 69 provides further detail on how article 69 is to be applied. Article 1 of the Protocol provides that the extent of protection should be a fair balance between (a) a strict literal interpretation of the claims; and (b) the claims being used merely as a guideline to what the patent-holder had contemplated, from a consideration of the patent’s description and drawings. Article 2 (added in 2000) states that due account must be taken of any element which is equivalent to an element specified in the claims.
The UK courts have, over the years, developed the principle of purposive construction, which involves carrying out an assessment of what the person skilled in the art (“PSA”) would understand the patent claims to mean. This was summarised by Lord Hoffmann in Kirin-Amgen as follows:
“34. 'Purposive construction' does not mean that one is extending or going beyond the definition of the technical matter for which the patentee seeks protection in the claims. The question is always what the person skilled in the art would have understood the patentee to be using the language of the claim to mean. And for this purpose, the language he has chosen is usually of critical importance. The conventions of word meaning and syntax enable us to express our meanings with great accuracy and subtlety and the skilled man will ordinarily assume that the patentee has chosen his language accordingly. As a number of judges have pointed out, the specification is a unilateral document in words of the patentee's own choosing. Furthermore, the words will usually have been chosen upon skilled advice. The specification is not a document inter rusticos for which broad allowances must be made. On the other hand, it must be recognised that the patentee is trying to describe something which, at any rate in his opinion, is new; which has not existed before and of which there may be no generally accepted definition. There will be occasions upon which it will be obvious to the skilled man that the patentee must in some respect have departed from conventional use of language or included in his description of the invention some element which he did not mean to be essential. But one would not expect that to happen very often.”
Thus, the basic principle is that the court would form a view on what the claims of the patent meant, taking into account the context to the invention as it would be understood by the PSA, and then would determine whether the alleged infringement fell within the scope of the claims.
Only in very limited circumstances could an alleged infringement with an element falling outside the literal meaning of the claims nevertheless be found to be infringing. The test commonly used to determine this was a three-step test known as the Improver/Protocol questions, and first set out by Lord Hoffmann in Improver Corp v Remington Consumer Products Ltd  FSR 181:
“If the issue was whether a feature embodied in an alleged infringement which fell outside the primary, literal or acontextual meaning of a descriptive word or phrase in the claim ('a variant') was nevertheless within its language as properly interpreted, the court should ask itself the following three questions:
“(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.
“On the other hand, a negative answer to the last question would lead to the conclusion that the patentee was intending the word or phrase to have not a literal but a figurative meaning (the figure being a form of synecdoche or metonymy) denoting a class of things which included the variant and the literal meaning, the latter being perhaps the most perfect, best-known or striking example of the class.”
Question 3 of the Improver test highlights that, in terms of previous UK law, though there was some scope for a variant to be found to be infringing, this could only happen where the PSA would understand the variant to fall within the figurative meaning of the word/phrase at issue. The Improver questions were thus still aimed at finding out what the PSA would understand to be the correct interpretation of the claim. And only if it fell within that interpretation could a product be found to infringe.
Issues in this case
Eli Lilly has a patent relating to the use of pemetrexed in treating cancer. It discovered that damaging side effects could be minimised by giving patents pemetrexed disodium (a type of pemetrexed salt), together with vitamin B12, and its claims covered this combination.
Actavis wished to launch products comprising other pemetrexed salts plus vitamin B12, being different salts to the one claimed in the patent but operating the same way. Actavis sought a declaration of non-infringement. As the Supreme Court noted at para 30:
“As a matter of ordinary language, it is quite clear that the only type of pemetrexed compound to which the patent’s claims expressly extend is pemetrexed disodium. One only needs to read claim 1 and claim 12 to justify that: as a matter of ordinary language, 'pemetrexed disodium' means that particular salt, and no other salt, let alone the free acid. If the first few words of each claim were not enough to make this good, the contrast between the specific reference to pemetrexed disodium and the wider reference to 'vitamin B12 or a pharmaceutical derivative thereof' underlines the point.”
New infringement test
The Supreme Court ruled that the question whether an item infringes a patent should be approached by addressing two questions through the eyes of the person skilled in the art (“PSA”):
- Does the item infringe any of the claims as a matter of normal interpretation?
- If not, although the item may be characterised as a variant, does it nonetheless infringe because it varies from the invention in a way which is immaterial?
The court noted that this new two-step test complies with article 2 of the Protocol, as question 2 squarely raises the principle of equivalents, but limits its ambit to those variants which contain immaterial variations from the invention.
At para 56, the court states that question 2 of the new test involves “not merely identifying what the words of a claim would mean in their context to the notional addressee, but also considering the extent if any to which the scope of protection afforded by the claim should extend beyond that meaning”.
The Supreme Court considered that in previous cases, the courts had wrongly conflated the two questions which now form part of the two-step test.
The court further advised that in answering question 2 of the new test, a reformulated version of the Protocol/Improver questions should be used, as follows:
- 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, i.e. 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 the previous version of the Improver/Protocol questions, it had to be obvious to the PSA, at the priority date of the patent, that the variant would achieve substantially the same result. This revised second question allows for variants, the effect of which would not have been obvious at the priority date, to be brought within the scope of the patent for infringement purposes.
The Supreme Court further warned that taking too literal an approach to interpretation would lead to the answer to question 3 always being yes, which should be avoided. In particular, the court stated at para 65 that “the fact that the language of the claim does not on any sensible reading cover the variant is certainly not enough to justify holding that the patentee does not satisfy the third question”.
Outcome and implications
It was clear that Actavis's products, also pemetrexed salts, would achieve the same result in the same way as the patented product. That would have been obvious to the PSA, particularly as the expert evidence suggested that the PSA would have investigated whether any of Actavis's alternative compounds worked, as a routine exercise.
On question 3, the court considered the PSA would not have assumed Eli Lilly was restricting its protection to pemetrexed disodium, even though that was the only substance claimed. The patent specification taught that other anti-folate drugs might work similarly. Eli Lilly had only carried out experiments on pemetrexed disodium, but that in itself would not mean that it intended to exclude other pemetrexed salts from the scope of protection.
The court also ruled that a patent’s prosecution history will only be relevant to issues of interpretation in certain exceptional cases.
This case has already generated much positive and negative commentary. The decision makes it clear that variants which fall outside the meaning of any normal interpretation of the claims can now be found to infringe, but provides relatively limited guidance on when, and in what circumstances this could be the case. The full implications of this will not be known until the lower courts start to grapple with the new test.
Of particular significance is how this new approach to interpretation in infringement cases will sit with interpretation when determining a patent's validity. It is common in patent cases for the alleged infringer to challenge the validity of the patent. In such cases, a “squeeze” argument is often run, in terms of which the alleged infringer will argue that if the patent is given a broad interpretation, so as to include the alleged infringement, it is invalid because of a piece of prior art which renders that broad interpretation anticipated and/or obvious. However, if the patent is given a narrow interpretation to overcome the prior art, the alleged infringement will not infringe. This was not at issue in the present case, because Actavis was not challenging the patent’s validity, but may well prove to be an issue in future cases.
Further decisions are awaited with interest!
In this issue
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- Too close to the wind? (1)
- The Land Register: two ticking timebombs
- Adult ADHD: a performance management issue
- Reading for pleasure
- Opinion: Sandra McDonald
- Book reviews
- President's column
- ScotLIS enters user test phase
- People on the move
- Priced out of justice
- The residence nil rate band – are your clients affected?
- State aid outside the EU
- IP actions at the Court of Session
- Give me liberty or give me a welfare attorney
- Personal injury trusts and professional trustees
- How to protect your firm and your clients from email fraud
- Court to child: a different approach
- Who can appeal a contempt ruling?
- Moveable property: reform at last?
- Too close to the wind?
- Limited partnerships and the PSC register
- Scottish Solicitors' Discipline Tribunal
- Recent changes to the PSG offer to sell
- Assigned standard securities
- On our own feet
- OPG tackles rising demand for PoAs
- Law reform roundup
- PI court timetable amended
- Reception greets Accredited Paralegal scheme
- Making paper history
- Your Law Society of Scotland Council members
- Master Policy renewal: it's easy online
- Ask Ash
- AML risks and company services
- Thinking of getting engaged?
- Q&A corner