Patents: insufficiency

Background

A patent is invalid if the 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) (1977 Act).

If it is possible to make a reasonable prediction, that the invention will work with substantially everything falling within the scope of the claim, it cannot be said that the claim is insufficient simply because the patentee has not demonstrated that the invention works in every case. If it is not possible to make a prediction, or if it is shown that the prediction is wrong and the invention does not work with substantially all the products or methods falling within the scope of the claim, then the scope of the monopoly will exceed the technical contribution the patentee has made to the art and the claim will be insufficient (Regeneron Pharmaceuticals Inc and another v Genentech Inc, www.practicallaw.com/4-525-3764).

Facts

F owned six patents relating to the use of enzyme inhibitors for treating anaemia. A applied to invalidate the patents to clear the way for their product, which was undergoing clinical trials. As well as alleging obviousness, A raised two insufficiency attacks against the patents: excessive claim breadth, and ambiguity or uncertainty. The patents were grouped into two families of three patents: family A and family B.

The Patents Court held that the family A patents were not obvious but all but one claim both lacked plausibility and could not be performed across their scope without undue burden (www.practicallaw.com/w-025-6561). So, they were invalid for insufficiency, while two claims were uncertain and so invalid for insufficiency.

F appealed on insufficiency for both patent families, and on obviousness in relation to family B. In relation to insufficiency F argued that, the Patents Court had been incorrect to rule that the skilled person had to be able to identify substantially all compounds covered by the claim without undue burden. The correctness of this principle was the major legal issue on appeal.

Decision

The court held that the family A patents were not invalid for insufficiency as lacking plausibility, which it preferred to call reasonable prediction, and imposing an undue burden. The family B patents were invalid for obviousness and A's product infringed all but one of the family A claims.

Following Regeneron, application of the reasonable prediction principle required three sequential steps:

• Identifying what fell within the scope of the claimed class.
• Determining what was meant by saying that the invention worked and identifying what it was for.
• Deciding whether it was possible to make a reasonable prediction that the invention would work with substantially everything falling within the scope of the claim (the three-step approach).

The Patents Court had incorrectly asked a single question: whether it was plausible that compounds within the structural class would have the claimed therapeutic efficacy, and had concluded that it was not. Whether that was the right question depended on the result of taking the three-step approach.

Applying the first step, what fell within the scope of the claim were compounds satisfying both the required structural features and the required functional features. Here, the conclusion at step one ought to have been that the claimed compounds were compounds within the relevant structures which satisfied tests for features C and E as set out in the patent. The answer to the second step was also clear. The fact that it was not necessary to demonstrate success in a clinical trial did not mean that the claims did not require the therapeutic effect to be achieved. At the third step, the question was whether it was possible to make a reasonable prediction that compounds which satisfied the structural features, and also the functional features C and E, would be useful to treat anaemia. This was clearly plausible.

Correctly construed, the patent did not promise explicitly or implicitly that substantially all the compounds which satisfied the structural definitions would have the claimed therapeutic efficacy, but only that compounds which satisfied both the structural definitions and the step one functional features would have the claimed therapeutic activity. The patent provided the new idea that a wide structural class of molecules which had the first functional feature contained members which did have the second functional feature able to produce the required therapeutic result. Identifying even a single compound with therapeutic efficacy based on a biochemical rationale not previously known to work could be a valuable technical contribution.

It must be possible to perform the invention across the scope of the claim without undue effort. The correct test is: for a claim with a functional feature which defines the claimed compounds, or a mix of structural and functional features, it has to be possible, without undue burden, both to identify compounds which satisfy the relevant test, and to find out whether any given compound satisfies the test. However, it is not necessary as a matter of law, simply because a claim contains functional features or a mix of functional and structural features, to establish for sufficiency that the skilled person can identify all or substantially all the compounds which satisfy the test.

Given the law does not require the identification of substantially all these compounds, the question remains of how many is enough. It has to be possible for the skilled person, without undue burden, to identify some compounds beyond those named in the patent, which are within the claimed class and therefore are likely to have therapeutic efficacy. It also has to be possible for the skilled person to work substantially anywhere within the whole claim. There must not be a specific region of the claimed scope for which testing the functional features will be an undue burden.

Here, the expert evidence showed that, although a great deal of work was required, the skilled team would have been able to find some compounds which were effective. It would take a great deal of work, but it would be routine for the medicinal chemist and iterative in nature. There was evidence that a significant number of compounds within the structural class as a whole would not work. This did not undermine the overall conclusion that some useful compounds would be found, nor did it indicate that there were particular regions of the claim scope which could not be tested. So the issue of undue burden did not arise.

Comment

As the court disagreed here on an important point of law with a senior patent judge in the Patents Court who is now also an appellate court judge, there are potentially different views on plausibility within the appellate court.

This decision shows that a claim of this type is not automatically invalid for insufficiency because it covers a potentially enormous number of compounds, and that the test for undue burden is not the cumulative burden of identifying and testing for efficacy all the compounds covered by the structural formula or the functional requirements of the claim.

Case: FibroGen Inc v Akebia Therapeutics Inc [2021] EWCA Civ 1279.

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