UK Supreme Court upholds Kymab's appeal imposing a stricter interpretation of sufficiency of disclosure for patents

By Neil Jenkins, Chris de Mauny


In a judgment handed down today the UK Supreme Court has upheld the appeal of Kymab who had challenged Regeneron's patents covering Kymab's 'Kymouse' transgenic mouse.

This decision will have a profound effect on the validity of many patents, particularly in the life sciences area, especially in biotech. The decision flows from the requirement under the European Patent Convention (of which the UK is a contracting state) that a patent provide sufficient disclosure of the invention it claims. This means that the patent must contain enough information for its invention to be reproduced by others without due burden. This basic principle has proved difficult to apply to patents with claims that may cover a range of products. Should a patent's monopoly be restricted to the specific information it provides or can the monopoly be broader if the patent discloses enough to make some of the product types in the range? Earlier English decisions, influenced by the European Patent Office case law, had allowed broader claims in circumstances where the products may all be produced using a principle that is of general application even if the patent does not disclose specifically how to make each type. 

By its decision today the Supreme Court has firmly confirmed sufficient disclosure as a basic ingredient of the 'patent bargain' which is understood to be the justification for patent monopolies. The monopoly is granted for a limited time in exchange for the patent holder providing (in the patent) sufficient information to allow the subject of the monopoly to be used by the public – once the monopoly expires.

As explained below, Regeneron's patents covering transgenic mice were said by Kymab to be over-broad, covering transgenic mice beyond those made possible by the teaching in the patents. Regeneron's case was that the patents disclosed a principle of general application for how to produce improved transgenic mice and this principle justified broader monopolies. For further details of the arguments put forward during the hearing in February, see our earlier report here.

The patents covered transgenic mice that were better for producing anti-bodies than previous transgenic mice, and methods for producing such mice. Transgenic mice for producing human antibodies had been produced previously by introducing into the mice's DNA the complete human gene sequence for the desired antibody. The antibodies thereby produced by the mice would be less likely to cause adverse immunological reactions in humans than antibodies produced from mixed human and mouse (murine) DNA. These were particular reactions known as 'HAMA' responses – human anti-mouse antibody responses. However, transgenic mice with full human antibody DNA sequences became "immunologically sick", meaning that they produced less effective antibodies compared with unmodified 'wild type' mice. Regeneron's researchers apparently solved these problems by producing transgenic mice with mixed human-murine DNA sequences for the antibodies and later modifying the antibodies produced by the mice in order to replace the murine portions with human portions, avoiding the HAMA response. These mice had what was termed a "reverse chimeric locus" in their DNA, whereby part of the human antibody DNA referred to as the 'human variable sequence' was replaced with a mouse variable sequence. The mice did not suffer significant immunological sickness and the HAMA response was avoided as well.

Kymab's case stemmed from the level of detail provided in the patents about how to introduce the reverse chimeric locus into the murine DNA. This had to be done in a precise, targeted way which Kymab argued left too much to the reader of the patents to do for themselves. Specifically, the patents' claims covered a wide range of sequence lengths and Kymab argued the skilled reader of the patents could not achieve the introduction of the reverse chimeric locus into the murine DNA across the whole range of what was covered at the relevant date.

In the end, the outcome here depended on the Supreme Court's analysis of what the monopoly was and what was required to enable it. The Court considered the monopoly was a range of product types (mice with different length reverse chimeric loci). In part this was because "murine immunological health is not an end in itself. It is a means to a different end" (paragraph 22), the "different end" being the effective production of antibodies from transgenic mice not suffering from immunological sickness.

What had to be enabled, therefore, was the making of mice with reverse chimeric loci across substantially the whole range – from short loci to long loci. The Court of Appeal had been in error on focussing on the benefit that the reverse chimeric loci gave (reduced immunological sickness) because this was not

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