SnIPpets | Intellectual Property Law Blog | Of mice and men: Supreme Court finds that Regeneron transgenic mouse patents are invalid for insuffiency | Fieldfisher
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Of mice and men: Supreme Court finds that Regeneron transgenic mouse patents are invalid for insufficiency



United Kingdom

On 24 June 2020, the Supreme Court held that Regeneron's patents for types of a transgenic mouse used for the development of human antibodies were invalid for insufficiency. In doing so, the Supreme Court reversed the Court of Appeal's earlier decision that the patents were valid and infringed, and re-affirmed the high threshold patents are required to meet in order to be sufficient. (The Supreme Court also published a very helpful Press Summary).


Under UK patent law, in order to patent an inventive product, a patentee must demonstrate that a skilled person can make the product by the use of the teaching disclosed in the patent coupled with the common general knowledge which is already available at the time of the priority date, without having to undertake an undue experimental burden or apply any inventiveness of their own. This requirement is labelled sufficiency. If the patent claims a range of products, it has usually been understood that the invention must be enabled over the whole of the range of products for which the claim is made for the patent to be sufficient.

Regeneron owned two patents which covered mice whose genes were modified to possess human antibody genes, allowing the mice to mirror a human's normal immune reaction and thus produce a broad spectrum of antibodies for therapeutic use. In 2013, Regeneron brought a patent infringement claim against Kymab, who counterclaimed that the patents were invalid for insufficiency. The High Court agreed that the patent was insufficient, on the basis that the one example in the patent – which required swapping DNA sequences of a large size – could not have been carried out at the priority date.

However, this decision was reversed by the Court of Appeal, which held that, given the radical nature of the invention and the fact that it had provided a 'principle of general application,' the patent was valid and sufficient. Essentially, the court felt it was unfair to limit Regeneron's monopoly to only the types of mice that could be made at the priority date, given that the invention was 'an inventive, indeed ground-breaking, general principle.' Kymab then appealed this decision to the Supreme Court.


The Supreme Court held that the Court of Appeal did not correctly apply the law as it stands, and had given undue weight to the idea behind the invention, rather than the claimed product itself. The question was whether or not the inventive product was enabled to be made by the disclosure, i.e. whether the skilled person could make it at the priority date. It was not enough that 'the benefits which the invention unlocked (in terms of preventing murine immunological sickness) would in due course be realised across the whole range [of mice.]'
The court emphasised that the Court of Appeal's analysis could not be regarded as a legitimate development of the law. To water down the sufficiency requirement in that way 'would tilt the careful balance thereby established in favour of patentees and against the public in a way which is not warranted by the EPC [European Patent Convention]'.


This is an important judgment which emphasises the requirement for patents to contain sufficient data to back up the 'inventive concept' claimed in the patent. Speculative patents will not be valid even where the inventive concept is original or ground-breaking, even if this means that the patentee is given a 'scant and short-lived reward for their efforts and ingenuity.'

Practically speaking, this judgment will have significant implications in the biotech industry, where companies are often faced with a difficult decision as to when to file a patent. The pressures of filing a patent early, including the need to beat out competitors to be 'first-to-file,' must be weighed carefully against whether the patent contains sufficient data and information for the inventive concept to be enabled at the priority date. While patentees are not required to give examples that each and every embodiment of a claim can be made, scientific companies should be conscious that third party competitors may well put to proof the sufficiency of their patents, especially when faced with infringement claims.

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