A patent represents a bargain between the patentee and the public - in return for a valuable 20 year monopoly right over use of the invention, the patentee discloses the invention to the world, thereby offering the ability to others to 'work the invention' after the monopoly has expired. In order to patent an inventive product, patent law requires that the skilled person in the art would be able to make the product by using the teaching disclosed in the patent, together with the common general knowledge available at the priority date, without undue experimental burden or having any inventiveness.
In the recent decision of Regeneron v Kymab, the Supreme Court has described this sufficiency requirement as a 'bedrock' of patent law, which prevents patentees obtaining a monopoly exceeding their contribution to the art. In particular, the Supreme Court had to consider sufficiency in circumstances where the invention was to a range of products – here, a ground-breaking range of types of genetically modified mouse – but the disclosure in the patent only enabled the skilled person to make some of the types of product in the range at the priority date.
The Court of Appeal, which found the patents valid, had clearly thought that limiting protection to only those products which the invention enabled to be made at the priority date gave "scant and short-lived reward for [the patentee's] efforts and ingenuity", in circumstances where public benefit would be derived from using its invention in future types of product. The Court of Appeal had therefore upheld the validity of the patents, concluding there was no need for Regeneron to disclose how to make the full range of mice because the idea was a "principle of general application".
The Supreme Court has overturned this decision, whilst recognising that the Court of Appeal's approach would increase the rewards for inventors in complex, rapidly developing areas like genetic engineering for treating diseases. The Supreme Court concluded it was settled law that, in relation to a product claim, substantially the whole of the range of products within the scope of the claim should be enabled to be made by the disclosure in the patent. Patentees may still rely, if they can, upon a principle of general application if it would appear reasonably likely to enable the whole range of products within the scope of the claim to be made. However, if the validity of the patent is challenged, the risk is that that 'general principle' will be established at trial not to have, in fact, enabled a significant, relevant, part of the claimed range to be made, as at the priority date. Further, the requirement to show enablement across the whole scope of the claim applies only across a relevant range (and not, for example, an irrelevant factor such as the length of the mouse's tail).
Interestingly, the decision of the Court of Appeal had been given by Kitchin LJ (as he then was), who was elevated to the Supreme Court in 2019 but could not, of course, participate in the Supreme Court hearing.
The case concerns two patents relating to transgenic mice that can be used as platforms for therapeutic antibody discovery. The patents claim the in situ replacement of mouse variable region immunoglobulin gene segments with human variable immunoglobulin gene segments, maintaining the mouse constant regions, so as to create a "reverse chimeric locus". The Supreme Court was told that hybrid mice incorporating the invention have a range of medical uses, including in relation to the potential development of antibody therapies against COVID-19.
Following the launch by Kymab of its 'Kymouse' in 2013, Regeneron sued for patent infringement. The Patents Court judge (the late Mr Justice Henry Carr) had found infringement established, but that all relevant claims were invalid for insufficiency. In particular, he said that there would be formidable difficulties in producing such a hybrid gene structure as claimed in the patents. The Court of Appeal, however, thought it could be achieved through the prior knowledge and disclosure in the patents, but only so as to produce a hybrid gene structure with a small sub-set of the human variable region. Transplantation of the whole of the human variable region into a hybrid gene structure was, in fact, only achieved by further inventive processes adopted subsequent to the patent.
Whilst the patents did not enable, at the priority date, mice at the more valuable end of the range to be made, the Court of Appeal had upheld the validity of the patents. It concluded that the disclosure in the patents was sufficient because the invention was a ground-breaking general principle, and it was sufficient if it could be seen that it would, in due course, benefit all products in the range, provided that at the priority date, the patent teaching enables at least one type of product in the range to be made immediately.
Having reviewed a series of UK and European Patent Office decisions, the majority of the Supreme Court (a majority of 4:1, with the majority judgment given by Lord Briggs, and a dissent by Lady Black) set out the following general principles relating to sufficiency:
- The sufficiency requirement exists to ensure that the extent of the monopoly conferred by the patent corresponds with the extent of the contribution which it makes to the art.
- For a product claim, the contribution to the art is the skilled person's ability to make the product itself, rather than (if different) the invention.
- Patentees are free to choose how widely to frame the range of products for which they obtain protection. However, they need to ensure that they make no broader claim than enabled by their disclosure.
- The disclosure required will, together with the common general knowledge at the priority date, be sufficient to enable the skilled person to make substantially all the types or embodiments of products within the scope of the claim.
- A claim which seeks to protect products which cannot be made by the skilled person using the disclosure in the patent will, subject to de minimis or wholly irrelevant exceptions, be bound to exceed the contribution to the art made by the patent.
- This does not mean that the patentee has to demonstrate in the disclosure that every embodiment within the scope of the claim has been tried, tested and proved to have been enabled to be made. Patentees may rely, if they can, upon a principle of general application if it would appear reasonably likely to enable the whole range of products within the scope of the claim to be made. But they take the risk, if challenged, that the supposed general principle will be proved at trial not in fact to enable a significant, relevant, part of the claimed range to be made, as at the priority date.
- A claim which in substance passes the sufficiency test will not be defeated by dividing the product claim into a range denominated by a wholly irrelevant factor (e.g. the length of a mouse's tail). The requirement to show enablement across the whole scope of the claim applies only across a relevant range. Broadly, a range will be relevant if it is denominated by reference to a variable which significantly affects the value or utility of the product in achieving the purpose for which it is to be made.
- Enablement across the scope of a product claim is not established merely by showing that all products within the relevant range will, if and when they can be made, deliver the same general benefit intended to be generated by the invention, regardless of how valuable and ground-breaking that invention may prove to be.
Applying these principles to the case, the Supreme Court majority concluded that the relevant claims 'clearly' failed for insufficiency. At the priority date, the disclosure of the patents, together with the common general knowledge, did not enable transgenic mice at the more valuable end of the range to be made. Therefore the claim to a monopoly across the whole of that range went far beyond the contribution that the product made to the art at the priority date. The Court of Appeal's approach had watered down the sufficiency requirement and had tilted the careful balance between a patentee and the public in an unwarranted way.