UK Supreme Court to assess plausibility of anaemia patents

Healthcare 3 min
December 23, 2022

The UK Supreme Court has just confirmed that it will hear the appeal in FibroGen Inc v Akebia Therapeutics concerning patents for treating anaemia and whether they lacked plausibility.

Green light for appeal

Perhaps buried by Christmas cards in the past week is news that the Supreme Court has given permission for the appeal in FibroGen Inc v Akebia Therapeutics to proceed. (The court granted leave on 3 October 2022, although this was not publicised on its website until 16 December 2022.)

Court of Appeal’s ruling: quick recap

In August 2021, the Court of Appeal reversed the decision of the Patents Court that patent claims for a broad class of compounds, defined by structure and function, to be used for treating specified types of anaemia were invalid for insufficiency as lacking plausibility and imposing an undue burden. FibroGen owned the patents and Akebia had applied to invalidate them to clear the way for their product, which was undergoing clinical trials. Arnold LJ had sat as the Patents Court judge.

Birss LJ who gave the principal judgment in the Court of Appeal analysed the case law on plausibility, which he preferred to call “reasonable prediction”. He concluded that there were three sequential steps to be followed, but the Patents Court judge had only applied a single test. When the three-step test was applied, there was no insufficiency on the basis of reasonable prediction.

Sir Christopher Floyd, who agreed with the decision of Birss LJ, gave his own judgment on sufficiency because they were “… differing from a patent judge of enormous experience and distinction, and the issues addressed in this case are of importance to the patenting of inventions in this important area of technology”.

For details of the Court of Appeal’s decision see our article: Patents: insufficiency – Bird & Bird ( (See also Sufficiency challenges keep pace with innovation – Bird & Bird ( which looks at the current and future importance of sufficiency in light of recent UK case law.)

Ramifications of the Court of Appeal’s decision

The Court of Appeal’s ruling sent encouraging signals to patent owners in the life sciences field. The judgments of the lord justices showed that patent claims for broad classes of compounds were not necessarily invalid for insufficiency because they covered a potentially enormous number of compounds. Similarly, the test for undue burden was not the cumulative burden of identifying and testing for efficacy all the compounds covered by the structural formula and/or the functional requirements of the claim.

It is not the first time the Supreme Court has looked at plausibility in recent years. As discussed by the Court of Appeal in this case, the Supreme Court had to grapple with it in the high-profile case of Warner Lambert v Generics [2018] UKSC 56.

Given the significance of the Court of Appeal’s decision and the fact that it overturned that of one of its own very experienced patents’ judges, it is perhaps not surprising that the Supreme Court has given the “green light” to another appeal.

Next steps

We do not yet know when the Supreme Court will hear this appeal but it is unlikely to be before next autumn. Stay tuned for further information!

Written by
Heidi Hurdle
Heidi Hurdle
I am the Professional Support Lawyer to Bird & Bird's market-leading Intellectual Property group in London. I have considerable experience in all areas of IP law (as both a fee-earner and PSL). As a City-based IP practitioner, I advised a broad spectrum of clients and conducted a number of high-profile cases, particularly in relation to patent and trade mark infringement. I also worked for the publication Practical Law for a number of years, where I was a Legal Editor in the IP and IT team, writing legal updates, practice notes and new precedents.

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