Regeneron v Kymab (UKSC, [2020] UKSC 27, 2020)

Dhenne Avocats · 11 October 2026

Our analysis

Summary

By a majority (Lord Briggs, with whom Lord Reed, Lord Hodge and Lord Sales agreed; Lady Black dissenting), the UK Supreme Court held claim 1 of Regeneron’s European Patent (UK) No 2 264 163, directed to a transgenic mouse, invalid for insufficiency. Where a product claim covers a range, the disclosure, together with the common general knowledge at the priority date, must enable the skilled person to make substantially all the types of product within a relevant range; it is not enough that every product in the range would deliver the same benefit once it could be made (para 56). The judgment settles the English test of sufficiency for range claims, a matter of real consequence for biotechnology platform patents.

Facts and procedure

Regeneron owns European Patents (UK) Nos 1 360 287 and 2 264 163, the latter a divisional of the former, both with a priority date of 16 February 2001 (para 13). They teach a « Reverse Chimeric Locus », a hybrid gene structure combining the murine constant region with all or part of the human variable region, designed to overcome the immunological sickness of mice used as platforms for therapeutic antibody discovery (paras 7, 11 and 12). Regeneron alleged that Kymab infringed claim 1 of the 163 Patent and claims 5 and 6 of the 287 Patent by offering its « Kymouse » to the pharmaceutical industry. The trial judge (Henry Carr J) found infringement but held all three claims invalid for insufficiency (para 13). The courts below construed that claim as covering a range of mice, defined in particular by the number of human V segments inserted, from one to 125 (paras 16 and 17). The Court of Appeal found that the teaching enabled only mice with a small subset of those segments to be made, but upheld sufficiency on the footing that the invention was a principle of general application benefiting the whole range (paras 4, 11 and 27).

The applicable law

The sufficiency requirement is laid down in Article 83 EPC, and insufficiency is a ground of opposition under Article 100(b); it is mirrored in sections 14(3) and 72(1)(c) of the Patents Act 1977, which section 130(7) requires to be read consistently with the Convention (para 29). The majority read them in the light of the case law of the EPO Boards of Appeal, notably Exxon/Fuel Oils (T 409/91) and Unilever/Detergents (T 435/91), and of the English authorities Biogen v Medeva and Kirin-Amgen (paras 31 to 55).

Question

Does a product claim whose teaching enables the skilled person to make some, but not all, of the types of product within its scope satisfy the sufficiency requirement where the invention would contribute to the utility of every product in the range, if and when it could be made (para 5)?

Decision

The majority set out eight principles (para 56). Sufficiency ensures that the extent of the monopoly matches the contribution to the art, which, for a product claim, is the ability to make the product itself. The disclosure must enable substantially all the types within a relevant range to be made. Showing that all products would deliver the same benefit, once they could be made, is not enough. Here, at the priority date the disclosure enabled only mice carrying a very small part of the human variable region to be made, while the extent of that region was then understood to be a very important factor in antibody diversity: the range was relevant and the claim went far beyond the contribution (para 57). The Court of Appeal had conflated the contribution with the invention (para 58), and its approach was not a legitimate development of the law (para 59). The appeal was allowed (para 61). Lady Black would have dismissed it: in her view the claim related to a principle of general application, deployed in every mouse across the range, and was therefore enabled (para 86).

Key points for practice

• For a product claim, the contribution to the art is measured by the products the skilled person can make at the priority date, not by the inventive idea (paras 56 and 58).
• The requirement of enablement across the scope of the claim applies only to a relevant range; a variable with no bearing on the value or utility of the product, such as the length of the mouse’s tail, is disregarded (paras 21 and 56).
• Reliance on a principle of general application remains open, but the patentee takes the risk that it does not in fact enable a significant part of the range (para 56).
• Practical point: the scope of a range claim must be tested against what the disclosure actually enables at the priority date; later inventions, including the patentee’s own, cannot cover the part of the range that could not then be made (paras 57 and 58).

Provisions applied

European Patent Convention

Art. 83; Art. 100

National law

Patents Act 1977 (United Kingdom), sections 14(3), 72(1)(c) and 130(7)

Case law cited

Regeneron v Kymab, [2018] EWCA Civ 671 (decision under appeal); Actavis Group PTC v ICOS, [2019] UKSC 15; Generics (UK) v Lundbeck, [2008] EWCA Civ 311 and [2009] RPC 13; Biogen v Medeva, [1995] RPC 25 and [1997] RPC 1; Kirin-Amgen v Hoechst Marion Roussel, [2005] RPC 9; Rockwater v Technip France, [2004] RPC 46; Chiron v Organon Teknika (No 3), [1994] FSR 202; May & Baker v Boots Pure Drug (1950) 67 RPC 23; EPO, T 226/85, T 292/85, T 361/87, T 409/91, T 435/91, T 694/92 and G 1/98; BGH, Dipeptidyl-Peptidase-Inhibitoren (X ZB 8/12)

Prepared by Dhenne Avocats from the text of the decision (UK Supreme Court website, official PDF of the judgment), consulted on 11 October 2026. Only the official text is authoritative.