In a judgment handed down on 24 June 2020, the UK Supreme Court (UKSC) overturned an earlier Court of Appeal ruling and decided two patents asserted by Regeneron against Kymab (EP1360287 and EP2264163) were invalid for reasons of insufficiency.

The patents related to the use of transgenic mice for the production of antibodies for use as therapeutics in humans. The inventors aimed to solve the problem of the “human anti-mouse antibody” (HAMA) response, which occurs when antibodies made in mice are administered to humans. The proposed solution was the so-called “reverse chimeric locus”, in which some of the human genes used to make antibodies in humans are inserted into the corresponding location in the mouse genome. The provision of mice with this reverse chimeric locus was the foundation of the Regeneron patents.

However, the specific replacement of the all the necessary genes (known as the V, D and J segments) with the human equivalents is very challenging due to the amount of DNA that must be targeted to a specific location in the mouse genome. In fact, it was not until several years after the filing of the original patents that specific and targeted replacement of all the V, D and J segments was actually achieved.

In the UK court proceedings, it was determined that, at the priority date, it was only actually possible to produce a mouse with a very small proportion of the relevant genes replaced in a targeted manner. Whilst the Court agreed this solved the problem of the HAMA response, the claim scope extended from this enabled embodiment to the much more ambitious goal of providing mice that had all the relevant genes replaced.

In the UKSC’s view, disclosing a single way of carrying out the invention was enough, “as long as there are suitable variants known to the skilled person through the disclosure or common general knowledge” that enable the rest of the claims scope. In Regeneron’s case, reliance on the common general knowledge was not possible because of the technical difficulties associated with the specific and targeted replacement of larger parts of the mouse genome.

It is clear the UKSC considered the breadth of the claims to be wider than justified by the contribution to the art, because only a small area of the invention could be put into practice at the priority date. The UKSC referenced the context of the invention and what they considered to be the problem it addressed, namely the provision of mice that can produce a diverse range of potentially useful antibodies for use in human therapy. Mice having only a small amount of the requisite antibody segments replaced with their human counterparts are limited in the diversity of antibodies they can produce. Mice having all of the requisite antibody segments replaced, are significantly more useful. This range of segment replacement is what the UKSC referred to as a “relevant range”. Where one falls on that range “significantly affects the value or utility of the product in achieving the purpose for which it is to be made”. The ability (or not) of the skilled person to provide products falling within that “relevant range” is therefore pertinent to sufficiency.

The UKSC opined that “the claim to a monopoly over the whole of that range went beyond the contribution which the product made to the art at the priority date, precisely because mice at the more valuable end of the range could not be made, using the disclosure in the patents”.

On that basis, the UKSC allowed Kymab’s appeal, revoking both patents.

Practice Points

  • Inception of an idea (in this case the concept of the reverse chimeric locus) and the reduction of that idea to practice across the claim scope are both required for an invention to be considered patentable.

  • When drafting applications, consider in detail the scope of each feature of your claims. If a feature is both (1) broad and (2) responsible for the advantages of the invention, consider including (optional) language in your specification that limits the breadth of that feature, in case you need to limit the scope of that feature during prosecution.

  • Consider whether the skilled person can (or cannot) put the invention into practice across its whole scope based on their common general knowledge.

  • Have detailed conversations with your inventors about each feature of the claims, and determine where the scope is justified (does the common general knowledge enable the remaining scope), or will more evidence or explanation might be needed on filing to support that scope.