Patents: validity and infringement of DNA-sequencing patents

The Patents Court has held that four out of five patents related to DNA-sequencing technology were valid and infringed, and has considered the meaning of the person skilled in the art when assessing obviousness and insufficiency.


An invention involves an inventive step if, having regard to the state of the art, it is not obvious to a person skilled in the art (Article 56, European Patent Convention; section 3, Patents Act 1977) (EPC) (1977 Act).

A European patent application must disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art (Article 83, EPC; section 14(3), 1977 Act).

The concept of the person skilled in the art therefore applies in two distinct circumstances, in relation to obviousness and insufficiency, and might be two different persons or teams. For insufficiency a person skilled in the art is the person or team to whom the patent is addressed and whose attributes, skills and common general knowledge are necessary to implement the patent (Schlumberger v EMGS [2010] EWCA Civ 819).

In Sabaf SPA v MFI Furniture Centres Limited and others, the House of Lords held that the two features of a gas burner were obvious and did not interact and so, despite the fact that there had not previously been a product that combined the two features, the law of collocation rendered the patent obvious (

In Regeneron Pharmaceuticals Inc v Kymab Ltd, the Supreme Court held that two patents for a transgenic mouse used for the development of human antibodies were invalid for insufficiency (


I sued M for infringement of its five patents relating to DNA-sequencing technology. M wished to sell DNA-sequencing systems in the UK. M denied infringement of any valid claim and claimed that the patents were invalid for obviousness and insufficiency.

M argued that the skilled person would be a team interested in or researching DNA sequencing by synthesis because the key piece of prior art did not relate to DNA sequencing. I argued this was incorrect as, at the priority date, there were no teams engaged in this specific research. I proposed instead a test based on an established field at the priority date.

M also argued that two of the claimed integers in one of I’s patents each performed the function for which they were already known in the art or which was obvious. Therefore, the patent claimed a mere collocation, so there was no inventive step (Sabaf).

On insufficiency, M argued that the patent claims covered later developed successful techniques which could not, without undue burden, have been performed by the skilled person across the full range of the claims, and needed further steps to make them work.


The court held that four of the five patents were valid as amended and infringed by one or more of M’s products. The fifth patent was invalid for lack of inventive step. If it had been valid, three of M’s products would have infringed, but one product would not have infringed, either directly or under the doctrine of equivalents.

Patents are directed to those likely to have a real and practical interest in the subject matter of the invention, including the devising of the invention as well as putting it into practice. In some cases, therefore, two different skilled persons may be relevant. The skilled person should not be defined too broadly or too narrowly.

Where it is necessary to define the skilled person for the purposes of obviousness in a different way from the skilled person to whom the patent was addressed, the approach to take is to start by asking what problem the invention aims to solve, and then to consider in which established field the problem could be located. The notional person or team in that established field is the relevant team making up the person skilled in the art. Here, the skilled person was a team working on research into sequencing, which was a more general characterisation than M’s.

The court rejected M’s challenge of insufficiency made in reliance on Regeneron. It does not matter that there are methods of sequencing that do not work or that some examples that work are not known at the priority date, as these variations are not relevant ranges for the purposes of the Regeneron insufficiency analysis. What matters for this type of range is that the skilled person can, without undue burden, identify examples of these methods of sequencing that will work as at the priority date.

The court also set out the principles for assessing obviousness in collocation cases. Before asking whether the invention involved an inventive step, it is necessary to decide whether it is a single invention or two or more inventions. If two integers interact on each other, if there is synergy between them, they constitute a single invention having a combined effect and the obviousness test applies to the idea of combining them. If each integer performs its own proper function independently of any of the others, then each is, for the purposes of obviousness, a separate invention and each has to be assessed separately.

The new or improved result claimed has to be the result of the relationship between the parts of the combination. This should be decided by reference to the claim, rather than with a focus on what is obvious from the prior art. There must be an interaction between the elements which the designer of the relevant product has to take into consideration, otherwise the claim will simply be a collocation of elements which perform their own functions independently of each other.

The court rejected M’s challenge to an expert called for I on the ground that, although he was a distinguished scientist, he had been asked to give evidence in a field that was not his own. The evidence of expert witnesses can be of assistance to the court regardless of whether the witness was working on the problem of the patent at the relevant time. The court also stressed the importance of expert witnesses giving candid and objective evidence and not arguing the case for the party calling them. The court may not place weight on evidence from an inventor given that inventors are unlikely to represent the skilled person armed only with the common general knowledge.


This decision provides a more general formulation of the principles set out in Regeneron for determining insufficiency and guidance on their application. It also provides a useful summary of the principles for defining the skilled person for the purposes of obviousness. In addition, the court’s practical points relating to expert witnesses are of interest.

Case: Illumina Cambridge Ltd v Latvia MGI Tech SIA and others [2021] EWHC 57 (Pat).

First published in the March 2021 issue of PLC Magazine and reproduced with the kind permission of the publishers. Subscription enquiries 020 7202 1200.

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