Reaffirming Sufficiency Requirements for Structural and Functional Patent Claims: FibroGen Inc v. Akebia Therapeutics Inc.

Introduction

In FibroGen Inc v. Akebia Therapeutics Inc. ([2021] EWCA Civ 1279), the England and Wales Court of Appeal (Civil Division) addressed crucial issues concerning patent validity and infringement within the pharmaceutical sector. The case revolved around six patents held by FibroGen, pertaining to the use of Hypoxia-Inducible Factor Prolyl Hydroxylase (HIF-PH) inhibitors for treating anemia associated with chronic kidney disease (CKD) and anemia of chronic disease (ACD). Akebia Therapeutics challenged these patents, alleging their invalidity based on lack of inventive step and insufficiency, as well as non-infringement. The appeal elucidated significant legal principles surrounding the sufficiency of patent claims that encompass both structural and functional features.

Summary of the Judgment

The Court of Appeal delivered a nuanced judgment, affirming the validity of FibroGen’s Family A patents concerning CKD anemia treatment while dismissing the claims related to ACD as obvious over prior art (WO 2004/108121). The court held that Family A patents were invalid due to insufficiency, as the claims lacked plausibility and imposed an undue burden by requiring the identification of numerous compounds without guaranteeing their efficacy. However, upon appeal, FibroGen successfully reversed the insufficiency finding for Family A, recognizing the patents as valid and infringed by Akebia’s vadadustat, a rival HIF-PH inhibitor. Conversely, Family B patents, which pertained to ACD anemia treatment, remained invalid for obviousness, as the court found that the use of HIF-PH inhibitors for ACD was an evident extension of existing knowledge.

Analysis

Precedents Cited

The judgment extensively referenced several landmark cases that shaped the court’s approach to patent sufficiency and inventive step:

Regeneron v Genentech ([2020] UKSC 27): This case established a structured two-stage approach to assessing sufficiency, focusing first on plausibility and then on undue burden.
Biogen Inc. v Medeva plc ([1977] R.P.C. 1): A seminal case that delineated the boundaries of sufficiency and claim breadth in patent law.
Idenix v Gilead ([2016] EWCA Civ 1089): Addressed the intersection of plausibility and inventive step, emphasizing the importance of claim construction in sufficiency assessments.
Actavis v ICOS ([2019] UKSC 15): Provided clarity on the "obvious to try" standard, balancing routine experimentation against inventive step requirements.
Mobil/Friction Reducing Additive G2 and Conor v Angiotech ([2008] UKHL 49): These cases discussed the relationship between inherent features and sufficiency, influencing the court’s view on the technical contribution of patent claims.

These precedents collectively informed the court’s interpretation of sufficiency, particularly regarding claims that intertwine structural definitions with functional capabilities.

Legal Reasoning

The court’s reasoning was methodical, adhering to established legal principles while addressing the unique complexities of the case:

Claim Construction: The court delved into the intricate structure of the patent claims, distinguishing between structural features (defining the chemical compounds) and functional features (specifying their inhibitory activity against HIF-PH). For Family A patents, claims combined both aspects, necessitating a precise understanding of what constituted a "structural mimetic of 2-oxoglutarate."
Insufficiency Assessment: Adhering to the two-stage approach from Regeneron v Genentech, the court first evaluated plausibility, determining whether the patent convincingly linked the structural features to the claimed therapeutic effects. It then assessed undue burden, scrutinizing whether the claims required excessive experimentation to identify effective compounds. For Family A, although initial findings suggested insufficiency, appeal arguments successfully demonstrated that the skilled team could reasonably predict and identify effective compounds without undue burden.
Obviousness Evaluation: For Family B patents, which targeted ACD anemia, the court found obviousness in light of prior art (WO 2004/108121). The use of HIF-PH inhibitors for ACD was deemed a natural extension of existing therapeutic strategies, lacking an inventive step.
Infringement Determination: The court meticulously constructed the claims to ascertain whether Akebia’s vadadustat fell within Formula I of the patents. It concluded affirmatively, reinforcing the infringement finding.

The court’s adherence to structured legal analysis, combined with a robust interpretation of precedents, underscored the importance of precise claim construction in patent validity assessments.

Impact

The judgment in FibroGen Inc v. Akebia Therapeutics Inc. has significant implications for future patent cases, especially within the pharmaceutical domain:

Clarification on Sufficiency: By reaffirming the sufficiency standards for claims that integrate structural and functional features, the court provided clearer guidance on how such patents must convincingly link claims to their practical applications without imposing undue burdens on the skilled person.
Obviousness in Pharmaceutical Patents: The decision underscores the necessity for inventive step beyond mere extensions of known therapeutic uses. Pharmaceutical companies must demonstrate substantial innovation when adapting existing compounds for new therapeutic targets.
Importance of Claim Construction: The case highlights the pivotal role of precise claim interpretation in determining patent validity and infringement. Clear delineation between structural and functional aspects within claims is essential to withstand validity challenges.
Guidance for Pharmaceutical Research: Researchers and patent drafters in the pharmaceutical industry must ensure that patent claims not only cover broad structural classes but also provide sufficient functional linkage to therapeutic efficacy, supported by plausible and demonstrable scientific rationale.

Overall, the judgment reinforces the delicate balance between broad patent protection and the necessity for clear, sufficient, and inventive claims, shaping the landscape for future pharmaceutical innovations.

Complex Concepts Simplified

HIF-PH Inhibitors

Hypoxia-Inducible Factor Prolyl Hydroxylase (HIF-PH) inhibitors are compounds that impede the activity of the HIF-PH enzyme. This enzyme plays a role in degrading HIF proteins, which are crucial for the body's response to low oxygen levels. By inhibiting HIF-PH, these compounds increase HIF levels, subsequently boosting the production of erythropoietin (epo), a hormone that stimulates red blood cell formation. Enhanced red blood cell production can effectively treat anemia, particularly in patients with chronic kidney disease.

Patent Claim Construction

Patent claim construction is the process by which courts interpret the language and scope of patent claims to determine what exactly is protected by the patent. It involves analyzing both the structural features (e.g., chemical composition) and functional features (e.g., biological activity) specified in the claim. Accurate claim construction is vital, as it directly impacts assessments of patent validity and infringement.

Insufficiency in Patent Law

Insufficiency refers to a situation where a patent claim does not provide enough information for a skilled person to carry out the invention. This can occur due to excessive claim breadth (covering too many compounds without adequate support) or lack of plausibility (failing to convincingly link claims to their intended effects). The two-stage approach assesses whether the patent makes a reasonable prediction that the invention will work across the claim’s scope and whether implementing it would impose an undue burden on practitioners.

Conclusion

The FibroGen Inc v. Akebia Therapeutics Inc. judgment landmarkly reinforced the standards for patent sufficiency and inventive step, particularly in contexts where structural and functional features are intertwined. By upholding the validity of Family A patents upon a refined analysis of sufficiency, the court underscored the necessity for patents to provide a clear, plausible, and non-overburdening blueprint for the invention's application. Concurrently, by invalidating Family B patents for obviousness, the court highlighted the relentless scrutiny that extended claims—those that naturally extend known uses—must endure. This dual outcome serves as a pivotal reference for future cases, emphasizing the importance of meticulous claim drafting and robust scientific underpinning in securing and defending patent rights within the pharmaceutical and broader technological arenas.