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Illumina Cambridge Limited v Latvia MGI Tech SIA & Others – the “chocolate teapot” theory

Posted: 21/04/2021

Earlier this year, Mr Justice Birss handed down his judgment in the case of Illumina Cambridge Limited v Latvia MGI Tech SIA & Others [2021] EWHC 57 (Pat). The judgment is the first application of the sufficiency principles set out in the Supreme Court’s landmark decision in Regeneron Pharmaceuticals Inc v Kymab Ltd [2020] UKSC 27, and clarifies that the principle applies to patented processes as well as patented products.

The case

The case related to patents owned by Illumina that derived from work by Solexa, a spin out company from Cambridge University bought by Illumina in 2007. The defendants, Latvia MGI Tech SIA and others in the Beijing Genomics Institute group (MGI), sought to sell DNA sequencing systems in the UK. Illumina brought an infringement action stating that MGI’s systems infringed five of its patents relating to DNA sequencing technology. MGI argued that the patents were invalid and denied infringement.

The patents in question covered modified nucleotides and fluorescent imaging. In particular, the inventions claimed in Illumina’s modified nucleotide patents related to using an azidomethyl group as a reversible chain terminator (RCT) in DNA sequencing by synthesis. 

To summarise the judgment, four of the patents (as amended during the proceedings) were found to be valid and infringed and one was found to be infringed but invalid for obviousness. This article focusses on two of the key arguments for invalidity, which related to obviousness and insufficiency.

Defendants’ key arguments


MGI’s first argument was that Illumina’s patents were obvious in view of a journal article from 1991 by Zavgorodny et al. This article disclosed azidomethyl nucleotides, but it failed to mention DNA sequencing or the use of RCTs. MGI argued that a skilled person was a team researching sequencing by synthesis using RCTs, so it would be obvious for a skilled person to use the RCTs disclosed in the Zavgorodny paper to improve sequencing by synthesis.


Section 72(1)(c) of the Patents Act 1977 states that a patent is liable to be revoked if “the specification of the patent does not disclose the invention clearly enough and completely enough for it to be performed by a person skilled in the art”.

MGI argued that Ilumina’s patents were insufficient by applying the Supreme Court's decision in Regeneron Pharmaceuticals Inc v Kymab Ltd. The Supreme Court held that Regeneron’s patent claims concerning the creation of a range of types of transgenic mice were insufficient. The issue before the Supreme Court was whether a disclosure was sufficient if the patent enabled only some, but not all, of the products within the claimed relevant range to be made. The court held that Regeneron’s patents were invalid for insufficiency as they did not enable the skilled person to perform the invention across the scope, or relevant range, of the claim without undue burden.

What did the High Court decide?


The definition of the “skilled person” for the purposes of determining obviousness was a key question. The main difference between the arguments of the two parties was whether the skilled person should be defined by reference to sequencing by synthesis methods.

Mr Justice Birss found that, for the purpose of considering obviousness, the person skilled in the art at the relevant priority date was a team working on research into sequencing by synthesis. This was a broader definition than that contended by MGI. The judge also found that the common general knowledge of the skilled person included knowledge of the concept of sequencing by synthesis with RCTs but that, as far as they were concerned, the idea had not succeeded. He held that there was nothing in the prior art to suggest that it had an application in relation to sequencing by synthesis using RCTs: a skilled person would "read it with interest and having done so, put it down and move on." The claims were consequently found not to be obvious.

“Regeneron” insufficiency

Mr Justice Birss confirmed that insufficiency as described in Regeneron applies to process claims as well as product claims. To be insufficient in a Regeneron sense, a skilled person would not be able to make a product within the relevant range across the entire scope of the claimed invention. If a range is relevant in the Regeneron sense, it must be enabled across the entire range without undue burden.

The skilled person must be able to make a suitable selection without undue burden for the claim to be sufficient, but the claim will not necessarily be insufficient because its scope covers things that have not yet been invented at the relevant date. The features that require enablement over the entire scope of the claim under Regeneron relate to the core inventive concept of the claim.

A chocolate teapot?

Mr Justice Birss illustrated the sufficiency point with an example of a patent claiming a new type of teapot that was inventive because it had a bespoke spout to prevent dripping. The claim may not specifically mention the material from which to make the teapot, as that is irrelevant to the invention. At the priority date, the skilled person would know that china would work to make the teapot and that chocolate would not work. The fact that the claim could be infringed later if a teapot was made using a new material that had not been invented at the priority date would not make the claim insufficient even though material is crucial to the teapot's function. The inventive concept would be the non-dripping feature, which does not relate to the material of the teapot.

The descriptive feature of the claim, that the teapot would need to be made of a suitable material, is not a relevant range according to Regeneron. Relevance of the Regeneron sense depends on examining all the circumstances: not just the language of the claim as drafted but the "essence or core” of the invention. The judge suggested that, in future, the ordinary descriptive or functional language used in most patent claims would be unlikely to be regarded as a relevant range in the Regeneron sense.

In applying this test to the Illumina patents, the judge held that the ranges put forward by the defendants were not considered to be the essence of the invention – they were not Regeneron ranges. The requirement to show enablement across the whole scope of the claim applies only if the patent specifies a "relevant range”. As a result, he held that the claims were sufficient.


This judgment is important as it applies and clarifies the Regeneron sufficiency principle and confirms that it applies to all patents – both for products and processes. It highlights that the relevant features of Regeneron sufficiency are those relating to the “essence of the invention” – the anti-drip spout is more important in this case than whether a chocolate teapot would be advisable!

This article has been co-written with Shamerah Neville, a trainee solicitor in the corporate team.

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