The Supreme Court has handed down today its judgment in Regeneron Pharmaceuticals Inc v Kymab Ltd [2020] UKSC 27, allowing Kymab’s appeal and holding Regeneron’s patents invalid for insufficiency by a majority of 4:1.

The judgment emphasises the fundamental principle of the patent bargain, which envisages that the patentee makes full disclosure of the invention in return for a time-limited monopoly. Sufficiency is, amongst other tools like novelty, inventive step and industrial application, one of the ways to ensure such patent bargain is struck in the right place, such that the protection afforded by the claim is commensurate with the technical contribution to the art made by the disclosure of the invention in the patent. Whilst the Lords and Lady of the Supreme Court were of the view that their judgment does not change the existing, fundamental legal principles of sufficiency contained in the well-established authorities in the UK and of the Technical Board of Appeal of the European Patent Office, this case illustrates the importance of, and difficulty in, identifying a patent’s technical contribution and the significant consequences which follow.


This appeal related to the validity of two of Regeneron’s patents EP(UK) No 1 360 287 and its divisional EP (UK) No 2 264 163. In essence, the invention in the patents was an innovative – and ground breaking – advance to develop “reverse chimeric mice” consisting in part of human and in part of murine elements, created by inserting parts of human variable regions into the mouse. Any mouse having this genetic structure (so-called Reverse Chimeric Locus) would avoid the problem of becoming immunologically sick and be more effective as platform for antibody production.

Claim 1 of EP’163 was to:

“A transgenic mouse that produces hybrid antibodies containing human variable regions and mouse constant regions, wherein said mouse comprises an in situ replacement of mouse VDJ regions with human VDJ regions at a murine chromosomal immunoglobulin heavy chain locus and an in situ replacement of mouse VJ regions with human VJ regions at a murine chromosomal immunoglobulin light chain locus.”

At [15] Lord Briggs giving the majority judgment of the Supreme Court characterised the claim as seeking a monopoly for the making of a genetically engineered mouse having two characteristics: first relating to what a mouse does (namely produce the hybrid antibodies described) and, second, what is contained in its genome (namely the Reverse Chimeric Locus).

It was not in dispute before the Supreme Court that Claim 1 was a product claim covering a range of types of mice. On the one end of scale, it would include mice with only a few human segments introduced into the mouse genome but was broad enough to capture mice with a whole of the human variable gene locus inserted. This was an important factor affecting the diversity of useful antibodies, with the gold standard in the art as at the priority date being viewed as the whole of the human variable region gene locus inserted as part of the hybrid antibody gene structure [58]. It was also not in dispute that Regeneron’s patents only enabled the skilled person to make products over a very small part of that range, at the least beneficial end [58].

Legal issue

Where the parties diverged was on the importance of the range of human genes incorporated into the chimeric mouse for the question of sufficiency. Regeneron argued that the existence of this range in Claim 1 was irrelevant, because “the unique advantage conferred by the use of a Reverse Chimeric Locus, namely a cure for the immunological sickness of the recipient mouse, worked across the whole range, regardless of the amount of the human variable region DNA inserted into the murine genome” [19]. In other words, the technical contribution was the solution to that technical problem (ie, preventing immunological sickness in the mice), which was delivered across the whole range captured by Claim 1 [20] and so the protection should be correspondingly broad.

Kymab, on the other hand, argued that the range of the human gene inserted was of key importance – and was part of the technical contribution –  because the amount of human genome inserted affected the ability of the mouse to produce a wide variety of B cells and so affected its effectiveness as antibody production platform. By not enabling the skilled person to produce substantially all of the embodiments falling within the claims, the appellant argued that the patent should fail for insufficiency.

Lord Briggs framed the legal question in this case as follows: “whether a product patent, the teaching of which enables the skilled person to make some, but not all, of the types of product within the scope of the claim, passes the sufficiency test where the invention would contribute to the utility of all the products in the range, if and when they could be made.” [5]

Legal principles relating to sufficiency

The Supreme Court starts its analysis of the law in the same way that it has previously when considering the questions of plausibility and inventive step, namely by reference to the patent bargain.  When considering the requisite bargain for a product claim, the disclosure to the public requires the teaching of the patent to enable to product to be made.  As a consequence, where a range of products is claimed, subject to de minimis exceptions,  the “essential patent bargain is not satisfied in relation to products in that part of the range which cannot be made, using the teaching in the patent” [25].

Having reviewed the authorities, Lord Briggs summarised eight key principles relating to the law on sufficiency at paragraph 56 of his leading judgment, with both his leading judgment and the dissenting judgment of Lady Black suggesting that there is little, if any, disagreement with the Court of Appeal as to the correct legal principles to be applied to sufficiency. The eight key principles set out by Lord Briggs are:

i) The requirement of sufficiency imposed by article 83 of the EPC 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.

ii) In the case of a product claim, the contribution to the art is the ability of the skilled person to make the product itself, rather than (if different) the invention.

iii) Patentees are free to choose how widely to frame the range of products for which they claim protection. But they need to ensure that they make no broader claim than is enabled by their disclosure.

iv) The disclosure required of the patentee is such as will, coupled with the common general knowledge existing as 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. That is what, in the context of a product claim, enablement means.

v) 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, measured as it must be at the priority date.

vi) 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.

vii) Nor will a claim which in substance passes the sufficiency test be defeated by dividing the product claim into a range denominated by some wholly irrelevant factor, such as 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. Put broadly, the 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.

viii) 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.

In addition to these principles the judgment of the Supreme Court emphasises that the determination of sufficiency is highly fact-specific and turns on how the person skilled in the art would interpret the patent and its claims at the priority date, with Lady Black in her dissenting judgment stating that this case turned on how the relevant claim was characterised and how the law is applied to the particular facts of this case.  What appears to have been crucial in this case was how the technical contribution of the patent was framed.

What is technical contribution?

On the one hand, the Court of Appeal and Lady Black focus their assessment of the technical contribution as being aligned with the “ground-breaking” innovative contribution of the patent in the disclosure of mice with a reverse chimeric locus that solved the problem of immunological sickness, with this invention being used in every reverse chimeric mouse irrespective of the “quantum of replaced material in the reverse chimeric locus”. In their view, to satisfy the requirement of sufficiency it was necessary for the skilled team to be able to produce transgenic mice incorporating the reverse chimeric locus and producing hybrid antibodies, and this they could do.  In Lady Black’s dissenting judgment, this was a fair protection across the breadth of the claim as “the range [of claimed reverse chimeric mice claimed with differing amounts of human genes] coincides with the technical contribution of the patents which was to solve the problem of immunological sickness, or putting it (loosely) another way, to facilitate the making of immunologically efficient mice” [86].

On the other, the majority view was that innovative contribution (even if ground breaking) was not the same as a patent’s technical contribution. This is reflected in the second of Lord Briggs’ eight legal principles which states “In the case of a product claim, the contribution to the art is the ability of the skilled person to make the product itself, rather than (if different) the invention.”  The case on sufficiency therefore turned on whether the range of human gene to be inserted in the reverse chimeric mice, as viewed from the perspective of the skilled person at the priority date, formed part of the technical contribution of the patent, or if it was irrelevant to it.

The Court agreed with Kymab that the range of human genes being incorporated into the chimeric mouse in the context of Claim 1 was relevant to the technical contribution of the patent. It did so by reference to the wording of Claim 1 but also by looking at the more general disclosure in the patent, based on which the skilled person would understand that the mice were not an end in itself, and were developed to, ultimately, produce a stream of antibodies in treating disease in humans. As such, the range was “understood to be a very important factor affecting the diversity of useful antibodies capable of being “discovered” by the use of transgenic mice… even though it did not affect the immunological health of the transgenic mouse” [57].

Accordingly, it was therefore necessary, save for de minimis exceptions, that the patent should disclose how to make the claimed antibodies from across the whole range of the claim.


The Supreme Court by majority of 4:1 (Lady Black delivering the dissenting judgment) held that Regeneron’s patents were invalid for insufficiency as they did not enable the skilled person to perform the invention across the scope of the claim, as on the facts of the case Claim 1 was broad enough to capture reverse chimeric mice that could not be made at the priority date (eg, mice with a whole or large part of the human variable gene locus inserted).

In doing so, Lord Briggs giving the majority judgment emphasised that the sufficiency requirement is a “bedrock” of patent law and this should not be developed or “watered down”  by the courts. In doing so he observed that  “It is settled law that in relation to product claims the sufficiency requires substantially the whole range of products within the scope of the claim to be enabled to be made as at the priority date, not by the contribution which the invention may make to the value and utility of products, the ability to make which, if at all, lies in the future” [60].

The Supreme Court noted the Court of Appeal’s consideration that confining the patentee with a ground-breaking invention to protection only over a range of products which the invention currently enables to be made at the priority date would give the patentee a “scant and short-lived reward for their efforts and ingenuity”.  However, it concluded that offering the patentee protection for embodiments that could not be made at the priority date would “tilt the careful balance thereby established in favour of patentees and against the public in a way which is not warranted by the EPC, and which would exceed by a wide margin the scope for the development of the law by judicial decision-making in a particular Convention state” [59]. It would grant to Regeneron a monopoly over the manufacture and exploitation of the gold standard chimeric mouse in the circumstances when its patent would not have enabled to make such a mouse at all. To allow such a claim would not be a fair bargain in light of how the Supreme Court had framed the relevant technical contribution of the patent.  Whilst this decision could be viewed as a harsh result in light of Regeneron’s efforts and ingenuity, the judgment shows the importance of identifying the correct technical contribution when considering validity of the patent.

Jonathan Turnbull
Jonathan Turnbull
+44 20 7466 2174
Monika Klajn
Monika Klajn
+44 20 7466 7604