Patents: invalidity for insufficiency across broad range of products claimed

By Audrey Horton



The Supreme Court has held that two patents for a transgenic mouse used for the development of human antibodies were invalid for insufficiency.


A patent may be revoked if its specification does not disclose the invention clearly and completely enough for it to be performed by a person skilled in the art (section 72(1)(c), Patents Act 1977).

A European patent application must disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art (Article 83, European Patent Convention) (EPC) (Article 83). Patent claims must be clear and concise and supported by the description (Article 84, EPC) (Article 84). Articles 83 and 84 give effect to the legal principle that a patent monopoly must be justified by the technical contribution to the art that the disclosure of the invention has made.


R sued K for infringement of two patents relating to the production of human antibodies using transgenic mice. These patents were based on a gene manipulation technique which inserted human gene elements involved in generating antibodies into a section of the corresponding mouse gene, overcoming a known problem which arose, resulting in mice suffering from a reduced immune response, or immunological sickness, which seriously impaired their efficiency as platforms for antibody development. 

The High Court held that the patents were invalid for insufficiency, but that, if they had been valid, K infringed some of the claims. Both parties appealed. The Court of Appeal reversed the High Court's decision and held that the patents were valid and infringed. K appealed.


The court allowed the appeal and held that the patents invalid for insufficiency.

The key question is whether a product patent, the teaching of which enables the skilled person only 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. The court held that the claims must be considered as directed to a product, and, at the priority date, the description in the patent did not enable the skilled person to make that product over the whole claimed range. In particular, what was enabled was the less valuable part of the range. Here, the product as currently made and marketed by both parties, which was undoubtedly of great value, was at the end of the range, which could only be made after further inventive developments by both parties. The Court of Appeal had wrongly concentrated on the inventive concept rather than on the claimed product which incorporated that invention.

Several key legal principles underlie the law of sufficiency. 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 the invention, if different. The disclosure required of the patentee is that which would, together 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. 

A claim which seeks to protect products which could not be made by the skilled person using the disclosure in the patent will, subject to de minimis exceptions, be bound to exceed the contribution to the art made by the patent, as measured at the priority date. 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 possible, on a principle of general application if it appears reasonably likely to  enable the whole range of products within the scope of the claim to be made. But patentees would be taking the risk, if challenged, that the supposed general principle would  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. 

Enablement across the scope of a product claim is not established merely by showing that all products within the relevant range would , if and when they  could be made, deliver the same general benefit intended to be generated by the invention, regardless of how valuable and ground-breaking that invention might prove to be.

Application of these principles to the facts here showed that the patents failed for insufficiency. At the priority date, the disclosure of the two patents, together with the common general knowledge, did not enable the transgenic mice to be made across the whole range claimed. The patents' claims related to all mice genetically modified to have a hybrid genetic structure, but the information in the patent would only allow the creation of a mouse containing a small amount of human genetic material, not the broad range claimed. The claim to a monopoly over the whole of that range went far beyond the contribution which the product made to the art at the priority date because mice at the more valuable end of the range could not be made using the disclosure in the patents.


This decision could have a profound effect on the validity of many patents, particularly in the life sciences area, where a range of product types may be covered by a patent's claims. The decision flows from the requirement under the EPC that a patent provide sufficient disclosure of the invention it claims. Previous case law had allowed broader claims in circumstances where the products may all be produced using a principle that is of general application. By re-enforcing the importance of the requirement for sufficient disclosure, this decision makes it clear that a patent's monopoly and teaching must correspond. Specifically, the correspondence must be between providing the information needed for others to make products across the monopoly, not to a monopoly believed to correspond to the range of products that will possess the same benefit but which cannot yet be made.

Case: Regeneron Pharmaceuticals Inc v Kymab Ltd [2020] UKSC 27.

First published in the August 2020 issue of PLC Magazine and reproduced with the kind permission of the publishers.  Subscription enquiries 020 7202 1200.