The UK Supreme Court (UKSC) has handed down its judgment in patent dispute Regeneron Pharmaceuticals Inc v Kymab Ltd ( UKSC 27 (24 June 2020), making key rulings for the law of 'sufficiency'.
The requirements for sufficiency of product claims
The UKSC ruled that for a patent claim to a range of products to be sufficient, it must be possible for the skilled addressee of the patent (the 'skilled person') to make substantially all the types or embodiments of such products across the scope of the claim at the relevant date.
This does not mean that the patentee has to demonstrate in the disclosure of the patent 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.
So, for example, consider a patent claim to products which include five types (A to E), all of which are disclosed to be more efficient or useful than their predecessors by the application to their manufacture of the same new invention. For the claim to be sufficient, the disclosure required of the patentee is such as will, coupled with the common general knowledge, be sufficient to enable the skilled person to make substantially all the types or embodiments of products within the scope of the claim – A to E, not just A and B. That is what, in the context of a product claim, enablement means.
However, a claim which seeks to protect products which cannot be made by the skilled person using the disclosure in the patent (coupled with the common general knowledge) will, subject to de minimis or wholly irrelevant exceptions, be bound to exceed the contribution to the art made by the patent. 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 how valuable and ground-breaking that invention may prove to be.
On the facts of the Regeneron v Kymab case, this meant that Regeneron's patent claim to reverse chimeric mice, made by the 'in situ replacement' of aspects of the mouse genome, was insufficient. This was because the patent claim covered a range of size of substitutions to the genome but the skilled person would only have been able to make a small proportion of such substitutions by employing the disclosure of the patent and their common general knowledge at the relevant date.
The Court of Appeal had overturned the first instance judge's finding of insufficiency because it said the law did not require that the patent specification necessarily enabled the skilled person to make or perform all of the embodiments of a claimed invention. The Court of Appeal said that in appropriate cases, a claim may embrace variants which may be provided or invented in the future and which achieve the same effect in a manner which could not have been envisaged without the invention. The technical contribution of Regeneron's patent was the concept of reverse chimeric mice, which avoided the immunological sickness of known chimeric mice, and this was a principle of general application that worked across the scope of the claim. However the UKSC concluded that the Court of Appeal had erred in this reasoning.
So in the terminology of a patent lawyer, it may perhaps be said that in the Regeneron case, the UKSC ruled that: a finding that a patent claim to a product is not insufficient for excessive claim breadth is no answer to a finding that the claim is classically insufficient.
The relevant date for assessment of insufficiency
The UKSC's judgment raises, however, a very notable question for the law of sufficiency: what is the correct date for the assessment of insufficiency?
This point was not in issue before the UKSC in the Regeneron case. However, with reference to an earlier House of Lords authority, Biogen v Medeva  UKHL 18, the UKSC said ():
"It is a general requirement of patent law both in this country and under the European Patent Convention ("EPC") that, in order to patent an inventive product, the patentee must be able to demonstrate (if challenged) 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. It is said that the invention must be enabled by the teaching in the patent."
Throughout its judgment, the UKSC continued to emphasise that the priority date of a patent is the date for the assessment of insufficiency.
Did the UK Supreme Court get the relevant date wrong?
However, in Biogen, Lord Hoffmann's ruling was clearly that the correct date for the assessment of insufficiency is the date of the application for the patent, which is also referred to as the 'filing date'. After discussing the impact of changes from the 1949 to 1977 Acts, in particular the removal of the 'lack of fair basis' ground for revocation and this not meaning that the principle underpinning the ground had been abandoned, Lord Hoffmann said ():
"Section 72(1)(c) [of the Patents Act 1977] can only give effect to this principle if the relevant date for compliance is the date of application. It would be illogical if a patent which ought to have been rejected under section 14(3) is rendered immune from revocation under section 72(1)(c) by advances in the art between the date of application and the publication of the specification."
Much of the House of Lords' reasoning in Biogen that would have been relied upon by the parties to the Regeneron case before the UKSC would have been drawn from earlier parts of the Biogen judgment, in which the House of Lords was considering the concepts of disclosure and enablement in the context of the challenge in that case to the claimed priority date of Biogen's patent. In that context, the House of Lords' reasoning was by reference to the priority date of the patent in issue. The UKSC seems to have missed this point entirely in its reasoning in the Regeneron case.
In fact, the UKSC's statement in  of its Regeneron judgment is also internally illogical: it refers to what is "disclosed in the patent". The patent is the document filed at the filing date, which may be up to a year after the priority date.
Consequences of the change to priority date (if it is here to stay)
If the date for the assessment of insufficiency really is the priority date, the tests for entitlement to priority and insufficiency have been conflated. This is because a patent will be invalid for insufficiency if the priority document (combined with the common general knowledge at the priority date) does not provide the skilled person with an enabling disclosure of the claimed invention of the patent (as eventually granted) – any additional material contained in the application for the patent, or which formed part of the common general knowledge at that date, would not be of assistance.
On the other hand if, as has long been understood to be the case, the date for the assessment of insufficiency is the filing date of the patent, the lack of an enabling disclosure in the priority document would mean only that information made available to the public in the priority year could become prior art for the purposes of the assessment of novelty and inventive step. In the assessment of sufficiency, additional supporting information included in the application as filed (for example, data from experiments demonstrating support for the claimed invention) forms part of the disclosure of the patent; the assessment of sufficiency addresses whether this disclosure enables the skilled person (with the benefit of the common general knowledge at the same date, the filing date) to perform the subject matter of the claim without undue burden.
This long understood approach is consistent, on its face, with section 14 of the Patents Act 1977, which states that the "specification of an application shall disclose the invention in a manner which is clear enough and complete enough for the invention to be performed by a person skilled in the art". It is a less generous approach for patentees than that taken under the previous UK legislation, the Patents Act 1949, for which the relevant date for assessment was the date of publication of the complete specification of the patent (which is after the filing date).
The long understood approach is also the foundation upon which patents have been drafted for decades.
It looks like patent litigators might need another trip to the UKSC to straighten this out.
The UK Supreme Court's judgment in Regeneron Pharmaceuticals Inc v Kymab Ltd ( UKSC 27 (24 June 2020) is available here.