A return to traditional threshold of Sufficiency in UK Patent Law following Regeneron Pharmaceuticals Inc vs Kymab Ltd?

Author: Lee Samuel |

2 Jul 2020


In the decision [2020] UKSC 27, dated 24 June 2020, the UKSC decided upon a longstanding dispute between Regeneron and Kymab.  The case concerned two Regeneron patents for the production of human antibodies using transgenic mice. Typically, human antibodies made by transgenic mice induce immunological sickness. However, this can be prevented by replacing part of the mouse antibody variable regions with human antibody variable regions thus producing hybrid antibodies containing mouse and human variable regions.

Kymab’s case focused on the concept of sufficiency in UK patent law, specifically in relation to product claims that cover a range of embodiments when the patent only contains data exemplifying a few. In short, how much supporting data is needed to uphold a broad claim. Kymab alleged the filed application, whilst disclosing antibody production when replacing several variable regions, did not disclose data showing that when replacing a large number/all of mouse antibody variable regions with human variable regions, in a single mouse, would lead to antibody production. Rather, Kymab alleged the filed application only disclosed success for a smaller range or subset. Regeneron countered it had met its disclosure obligations even though it had not specified precisely how all the claimed products may be made.

The UKSC decided in Kymab’s favour, and invalidated both of the EP(UK) patents for insufficient disclosure stating that the two patents only enabled the skilled person to make products across what it assessed to be part of the claims.


UK and EP law consistently state that a set of claims to a single product or a range of products has to be “sufficiently disclosed”, which means that the skilled person must be able to put the invention into effect across the entire scope of the claims, on reading the filed application using no more than common general knowledge and without “undue experimental burden”.  This ensures the extent of the granted patent monopoly corresponds with the extent of the contribution the patent disclosure makes to the art

The present decision reminds us that a patent claim to a product lacks sufficient disclosure if it is not possible on reading the first filing to make substantially all the products that fall within its scope.  Judging the amount of data to put in a patent application, having regard to the amount of protection required, is a skill underpinned by a vast knowledge of case law, so consult with your patent attorney before filing. Moreover, consider carefully when to file; filing too early and with insufficient data may curtail protection or even make the patent vulnerable to revocation for lack of sufficiency.

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