The Court of Appeal has held that two patents for the production of human antibodies using transgenic mice were not invalid for insufficiency.


A patent may be revoked on the ground of insufficiency if the specification of the patent 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 1973) (EPC). The claims must be clear and concise and supported by the description (Article 84, EPC). 
The skilled person or team must be able to perform the invention without undue effort. The sufficiency of the description will be assessed having regard to the nature of the invention, the character of the technical field in which the invention was made and the abilities of the skilled team. 


R brought an action against K alleging infringement of two patents relating to the production of human antibodies using transgenic mice.

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 held the patents were valid and that K's mice infringed the product, although not the process, claims of the patents. 

The legal issue at the heart of the insufficiency allegation was the extent to and the manner in which an invention had to be enabled across the whole scope of the claim.

According to EPO case law, a specification did not necessarily have to enable the skilled person to make or perform all of the embodiments of a claimed invention. A claim might embrace variants which might be provided or invented in the future and which achieved the same effect in a manner that could not have been envisaged without the invention. The assessment of insufficiency had to be sensitive to the nature of the invention and the particular facts. If the character of the invention was one of general methodology, or the invention was of general application, then it might be permissible to claim it in general terms, even though the specification did not enable every way of arriving at its subject matter. It was a general principle that the protection afforded by the claims had to correspond to the technical contribution to the art made by the disclosure of the invention. The patentee was entitled to fair protection having regard to the nature and character of the invention described.

According to UK case law, the extent of the patent monopoly, as defined by the claims, had to correspond to the technical contribution to the art its disclosure had made for it to be justified. The specification had to enable the invention to be performed to the full extent of the monopoly claimed. But if the invention disclosed a principle capable of general application, the claims might be in correspondingly general terms. If the patentee had found a new product that had a beneficial effect, but could not demonstrate that there was a common principle by which that effect would be shared by other products of the same class, he would be entitled to a patent for that product but not for the class. But if he had disclosed a beneficial property which was common to the class, he would be entitled to a patent for all the products of that class even though he had not himself made more than one or two of them. There was more than one way in which the breadth of the claim might exceed the technical contribution to the art embodied in the invention. The patent might claim results that it did not enable, such as making a wide class of products when it enabled only one of those products and disclosed no principle which would enable others to be made. Or it might claim every way of achieving a result when it enabled only one way and it was possible to envisage other ways of achieving that result which made no use of the invention.

The disclosure of the gene manipulation technique was a major contribution to the art because it provided the answer to a significant problem which those working in the field had faced, namely that transgenic mice produced by conventional methods were immunologically sick. Transgenic mice with the patented technique did not suffer from this deficiency. So, any transgenic mouse that fell within the scope of the claims would benefit from the technical contribution the disclosure the patent had made to the art. It was properly described as a principle of general application.

The skilled team, equipped with the common general knowledge, could have produced, without undue effort, a transgenic mouse falling within the scope of the claim and this could have been achieved by conventional techniques. Although it was not possible at the priority date to perform an example in one of the patent specifications, or to insert the complete relevant human gene, this did not make the disclosure insufficient. The law did not require a patentee to enable every embodiment of a claimed invention and, if the claim of a patent was adequately enabled across its breadth, and its scope was commensurate with the technical contribution the disclosure of the invention has made to the art, the patent did not cease to be sufficient simply because the specification promised too much. 


Key to the decision was the evidence given which showed that R's discovery of the patented process was a broad invention of general application. Having established this, the patent claims were less likely to be held invalid for insufficiency and more likely to be found to be infringed. 

The court reviewed both the EPO and UK law on insufficiency. UK courts have the benefit of more expert evidence than the EPO and it is interesting to note that the evidence on which the court based its decision was that provided by K's experts for the purpose of novelty. This is a classic example of the squeeze between demonstrating that a prior art document is enabling, and so novelty-destroying, of a claim, and subsequently attempting to prove that the same claim is insufficient. 

Case: Regeneron Pharmaceuticals, Inc v Kymab Ltd and another [2018] EWCA Civ 671.

First published in the May 2018 issue of PLC Magazine and reproduced with the kind permission of the publishers. Subscription enquiries 020 7202 1200.

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