Court clarifies law on pharma patent claims

Sarah Taylor and Nicole Jadeja of Pinsent Masons, the law firm behind Out-Law, were commenting after the court considered the standards of disclosure that apply to complex pharmaceutical patents, and in particular those patents which contain claims with functional features and mixed structural/functional features. 

Disclosure requirements are a feature of patent law. They are designed, among other things, to ensure that people can understand what the scope of a patent is and what invention it claims.

In its ruling, in a dispute between FibroGen and rivals Akebia Therapeutics and Otsuka Pharmaceutical, the Court of Appeal considered disclosure requirements as they apply to the concept of ‘sufficiency’ in UK patent law. This is a developing area of patent law in the UK, particularly in the context of the life sciences sector and pharmaceutical patents. It has been recently considered by the Supreme Court, and was further clarified by Lord Justice Birss who gave the leading judgment for the Court of Appeal in this case.

Section 72(1)(c) of the Patents Act 1977 states that a patent is liable to be revoked if "the specification of the patent does not disclose the invention clearly enough and completely enough for it to be performed by a person skilled in the art". This is colloquially referred to as classical insufficiency, and the relevant date for assessing that sufficiency is the time the patent application was filed.

There are other forms of insufficiency too that have been established by case law. Excessive claim breadth, also known as ‘Biogen’ insufficiency, occurs when a claim extends beyond the technical contribution of the patent, and so does not support the invention. Uncertainty insufficiency is another category of insufficiency and applies where the language used in the patent claims is so ambiguous that it renders the patent invalid for not disclosing the invention clearly enough.

Case law has also established the concept of plausibility in respect of insufficiency, amongst other areas of patent law. In the context of insufficiency, this requires that the assertion that the invention will work across the scope of the claim must be plausible or credible. 

It is established case law in England and Wales that the question of whether the requirements of sufficiency are met boils down to whether the skilled person can readily perform the invention over the whole area claimed without undue burden and without needing inventive skill.

In its ruling, the Court of Appeal has clarified how the case law applies in the context of pharmaceutical patents where the claims made about the underlying invention are defined in both structural and functional terms. The court overturned the High Court’s decision in respect of insufficiency, holding that the judge applied an unnecessarily high threshold for measuring the sufficiency of claims with structural and functional features.

The importance of this decision was highlighted by one of the judges who was ruling on the case for the Court of Appeal, Sir Christopher Floyd. He agreed with Lord Justice Birss, and said that "... on the issues of sufficiency, we are differing from a patent judge of enormous experience and distinction [Lord Justice Arnold, who ruled on the case for the High Court], and the issues addressed in this case are of importance to the patenting of inventions in this important area of technology”.

The Court of Appeal disagreed with Lord Justice Arnold’s decision that “the skilled person or team must be able to identify substantially all compounds covered by the claim without undue burden” to avoid insufficiency on the basis of excessive claim breadth.

Instead, the Court of Appeal said it will be enough that it is “possible to make a reasonable prediction the invention will work with substantially everything falling within the scope of the claim” provided that the skilled person can identify some of those compounds, beyond those already named, and are able to work substantially at any point across the structural class in that regard without undue burden.

Lord Justice Birss proposed a three-stage test for plausibility, or what he said may be more appropriately called “reasonable prediction”. This, he said, should entail firstly identifying what it is which falls within the scope of the claimed class; secondly, determining what it means to say that the invention works – i.e. asking what is it for; and thirdly, asking whether it is possible to make a reasonable prediction the invention will work with substantially everything falling within the scope of the claim.

Nicole Jadeja, life sciences partner at Pinsent Masons, said “In re-framing the critical question on sufficiency as requiring only some, and not all, compounds falling within the claim to be found effective, the Court of Appeal clarified that, for the purposes of assessing if this could be done without undue burden, it does not matter if any research project involves a lot of work or is lengthy. It only matters that it can be done with undue burden, for example, because the necessary testing is routine and iterative.”

“The question which will now be central to future cases on this type of insufficiency is how many compounds or molecules need to be found effective. This is necessarily a fact specific question which means we will inevitably see more cases testing the boundaries of the law of insufficiency,” she said.

The court also clarified the law in relation to uncertainty insufficiency. It said that there is a distinction to be drawn between a claim that is difficult to construe, or which has some room for doubt or fuzziness at the edge, and one that is conceptually uncertain. It said that where experts cannot agree on exactly where the claim boundary lies, this would undermine any claim for patent infringement but not render the patent invalid on the basis of uncertainty.

“The ruling will be welcomed by those in the pharmaceutical industry,” Taylor said. “It offers important guidance to pharmaceutical manufacturers as many pharma patent claims are framed with a structural feature and double functional features.”

“The ruling is positive from an innovator’s point of view, as well as providing some clarity for those who draft patents. It means that patents for broad chemical formulae when the therapeutic effect of the compounds covered by the formulae is included in the claims may be less vulnerable to sufficiency attacks than if the High Court’s original decision had stood, and therefore may give pharmaceutical manufacturers increased confidence in the strength of such patents. Arguments that such patents claim inventions which are too broad, the limits of which cannot be ascertained even through an extensive research project, will need to be far more nuanced and expert evidence is vital in this regard,” she said.

Jadeja said: “Interestingly, the decision brings the law in England and Wales in line with the German Supreme Court decision in the case concerning Dipeptidyl-Peptidase-Inhibitoren, which the Court of Appeal found to be highly relevant. It noted that the German ruling was not considered by the High Court in this case. If this case is anything to go by, the UK courts, as many predicted, still seem keen to algin with European Patent Office decisions and European case law where it can.”

The Court of Appeal was considering the issues in the context of a dispute over the validity of patents owned by FibroGen for a product used to treat chronic kidney disease anaemia and related conditions, and whether rival companies Akebia Therapeutics and Otsuka Pharmaceutical, who are both engaged in clinical trial testing for a rival product, infringed those patents. The High Court previously ruled in favour of Akebia and Otsuka.

At the heart of the High Court’s decision was its view that both families of patents in dispute in the case – family A and family B – were lacking in sufficiency. However, after hearing the arguments on appeal, the Court of Appeal reversed the High Court’s findings in relation to sufficiency. The court considered that the ‘family A’ patents of FibroGen’s were valid after all and that they had been infringed. It held, however, that the ‘family B’ patents were still invalid on the basis that the underlying invention was obvious.