FibroGen Inc v Akebia Therapeutics Inc ([2021] EWCA Civ 1279): Establishing the Limits of Sufficiency in Patent Claims with Mixed Structural and Functional Features

Introduction

FibroGen Inc v Akebia Therapeutics Inc ([2021] EWCA Civ 1279) is a seminal case adjudicated by the England and Wales Court of Appeal (Civil Division) that delves into the intricacies of patent validity and infringement in the context of pharmaceutical innovations. The case revolves around six patents owned by FibroGen, which were exclusively licensed to Astellas Pharma Inc, pertaining to the use of Hypoxia-Inducible Factor Prolyl Hydroxylase (HIF-PH) inhibitors for treating anaemia, specifically chronic kidney disease (CKD) anaemia and anaemia of chronic disease (ACD).

The primary legal issues at hand involve the sufficiency of patent disclosures, the breadth of patent claims encompassing both structural and functional features, and the principles governing patent infringement. Akebia Therapeutics Inc. and Otsuka Pharmaceutical Company Ltd. contested these patents on grounds of invalidity and non-infringement, prompting an extensive legal examination of patent law as it applies to complex biochemical inventions.

This commentary dissects the judgment, elucidating the court's analysis, legal reasoning, precedents cited, and the broader implications for future patent litigation and drafting.

Summary of the Judgment

The Court of Appeal delivered a comprehensive judgment addressing both Patent Families A and B owned by FibroGen. The key conclusions are as follows:

• Family A Patents: These patents were declared invalid due to insufficiency in disclosure. The claims were deemed excessively broad, lacking plausibility, and unable to be performed across their entire scope without undue burden.
• Family B Patents: These were invalidated on the grounds of obviousness. The court found that the prior art (WO 03/053997 and WO 2004/108121) made the claims obvious to a person skilled in the art.
• Infringement Findings: The court concluded that vadadustat falls within Formula I as defined in the patents, thereby infringing the valid Family A patents. However, Family B patents were invalidated regardless of infringement considerations.

Consequently, the appeal was partially allowed concerning Family A patents while being dismissed on grounds of obviousness for Family B patents. The respondent’s notice challenging the construction of vadadustat within Formula I was also dismissed.

Analysis

Precedents Cited

The judgment extensively cites and builds upon several foundational cases in patent law, particularly:

• Biogen Inc v Medeva plc ([1977] R.P.C. 1): Established the principle that if an invention discloses a principle capable of general application, claims may be made in general terms without demonstrating applicability in every instance.
• Regeneron v Genentech ([2020] UKSC 27): Clarified the sufficiency of disclosure, especially concerning plausibility and undue burden in patents with broad claims.
• Idenix v Gilead ([2016] EWCA Civ 1089): Highlighted the importance of assessing the technical contribution of a patent independently of partial non-inventive steps.
• Unwired Planet v Huawei ([2016] EWHC 576 (Pat)): Addressed the distinction between claims that are simply fuzzy and those that are conceptually uncertain, reinforcing the need for clarity in patent claims.

These cases collectively inform the court’s approach to evaluating patent sufficiency, claim breadth, and the necessity of enabling disclosure across the full scope of patent claims.

Legal Reasoning

Claim Construction

A pivotal aspect of the judgment is the construction of patent claims that incorporate both structural and functional features. The court scrutinized how these claims define the scope of the invention and the obligations of the patentee to sufficiently disclose the invention.

For Family A patents, the claims were interpreted as encompassing a broad class of heterocyclic carboxamides defined structurally and by their function of inhibiting HIF-PH enzyme activity in treating CKD anaemia. The court found that the patent did not provide adequate information to perform the invention across its entire claimed scope without undue burden, leading to a declaration of insufficiency.

In contrast, for Family B patents, the claims were considered obvious in light of prior art. The functional iron deficiency claims, intended to treat ACD, did not present an inventive step over the disclosed HIF-PH inhibitors known for treating anaemia.

Sufficiency of Disclosure

The court applied a two-stage inquiry to assess sufficiency:

• Plausibility: The patent must make it plausible that the invention works across the entire scope of the claims.
• Undue Burden: It should not require excessive effort for a person skilled in the art to make or use the invention across the full claim scope.

For Family A patents, the court concluded that the claims were not plausible as the patent lacked evidence that the vast majority of compounds within the structural class were effective. Additionally, conducting a comprehensive search for valid compounds would impose an undue burden on practitioners.

Obviousness

Regarding Family B patents, the court determined that the use of HIF-PH inhibitors for treating ACD was an obvious extension of existing knowledge. The prior art already suggested such applications, and the patents did not showcase a novel or non-obvious benefit over established treatments like ESAs.

Infringement

The court examined whether vadadustat, a rival HIF-PH inhibitor developed by Akebia, fell within the scope of Formula I as defined in Family A patents. It concluded affirmatively, thereby recognizing infringement. However, since Family A patents were rendered invalid, this infringement finding primarily highlighted the invalidity issues rather than establishing enforceability.

Impact

This judgment has far-reaching implications for patent law, especially within the pharmaceutical sector:

• Patent Drafting: Innovators and patent attorneys must exercise caution in drafting claims that intertwine structural and functional elements. Overly broad claims without robust supporting evidence may be susceptible to invalidation for insufficiency.
• Innovation Incentives: While broad claims can protect wide-ranging applications of an invention, this case underscores the necessity for sufficient disclosure to inspire further innovation without unfairly monopolizing an expansive territory.
• Litigation Strategy: Competitors may more confidently challenge patents on grounds of insufficiency and obviousness, particularly when claims are composed of dual structural and functional features.

Furthermore, the judgment reinforces the importance of aligning patent claims closely with the disclosed invention, ensuring that they are neither too vague nor impossibly broad.

Complex Concepts Simplified

Sufficiency of Disclosure

This refers to the requirement that a patent must provide enough detail for someone skilled in the field to make and use the invention without undue experimentation. If a patent claims a broad range of applications or compounds, it must convincingly demonstrate that these can all be realized as claimed.

Obviousness

A patent claim is obvious if it lacks a sufficient inventive step beyond existing knowledge. If a person skilled in the art would find the invention logically deducible from prior art, the patent can be deemed invalid for being obvious.

Structural and Functional Features in Claims

Patent claims often define inventions by their structure (the physical or chemical composition) and their function (what they do). Balancing these elements is crucial; claims should not be so broad structurally that the function cannot be consistently achieved across all variations.

Markush Formula

A Markush formula is a way of defining chemical compounds in patents by listing possible variations (e.g., different substituents). It allows for the protection of a group of related compounds under a single patent claim.

Conclusion

The FibroGen Inc v Akebia Therapeutics Inc ([2021] EWCA Civ 1279) judgment serves as a critical benchmark in patent law, especially within biotechnology and pharmaceutical spheres. It underscores the necessity for patents to maintain a delicate balance between claim breadth and sufficiency of disclosure. Overly ambitious claims that blend structural and functional attributes without ample supporting evidence risk being invalidated for insufficiency or obviousness.

For practitioners, this case emphasizes the importance of ensuring that patent applications provide a clear, detailed, and plausible disclosure that aligns with the scope of the claims. Broad claims must be underpinned by comprehensive evidence demonstrating that the claimed functionalities are achievable across all encompassed variations.

Moving forward, innovators and legal professionals must heed these judicial clarifications to fortify patent validity, thereby safeguarding genuine innovations while fostering a competitive and fair marketplace.