Introduction

The case of FibroGen Inc v. Akebia Therapeutics Inc ([2021] EWCA Civ 1279) is a landmark judgment delivered by the England and Wales Court of Appeal (Civil Division) on August 24, 2021. This case revolves around patent disputes concerning the use of hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitors for the treatment of anemia associated with chronic kidney disease (CKD) and anemia of chronic disease (ACD).

The central parties involved are FibroGen Inc., the patent holder and appellant, and Akebia Therapeutics Inc. alongside Otsuka Pharmaceutical Company Ltd., the respondents. Additionally, Astellas Pharma Inc. is an appellant involved in a separate but related claim.

The core legal issues addressed in this case include:

• Validity of patents based on insufficiency and obviousness.
• Infringement claims related to competing HIF-PH inhibitor drugs.

Summary of the Judgment

The Court of Appeal meticulously examined two families of patents held by FibroGen:

• Family A: Concerned the use of HIF-PH inhibitors for treating CKD-related anemia.
• Family B: Pertained to the use of the same inhibitors for treating ACD.

The High Court had previously invalidated Family A patents on grounds of insufficiency and Family B patents on the basis of obviousness. Upon appeal:

• Family A Patents: The Court upheld the High Court’s decision, affirming that the patents lacked sufficient disclosure and their claims were excessively broad.
• Family B Patents: The appeal concerning the obviousness of Family B patents was dismissed, maintaining the High Court’s decision of invalidity.

Additionally, interlocutory aspects regarding whether the rival drug vadadustat fell within the scope of the patents were addressed, with the Court confirming that vadadustat did infringe Family A patents under normal construction but rejected the infringement claims related to specific symptomatic equivalence.

Analysis

Precedents Cited

The judgment extensively referenced several pivotal cases to underpin its analysis:

• Regeneron v Genentech: Influenced the two-stage approach to assessing patent sufficiency, focusing on plausibility and undue burden.
• Idenix v Gilead: Addressed the concept of inventive step and the necessity of reasonable prediction of efficacy across claim scope.
• Biogen v Medeva: Established principles regarding the use of functional language in patent claims and sufficiency of disclosure.
• Bundesgerichtshof, Dipeptidyl-Peptidase-Inhibitoren: German Supreme Court decision influencing the interpretation of functional limitations in patent claims.
• Actavis v ICOS: Provided guidance on avoiding stepwise analysis in obviousness and the relevance of expectation of success.

These precedents collectively shaped the Court’s approach to evaluating the sufficiency and obviousness of the patents in question, especially concerning claims combining structural and functional features.

Legal Reasoning

The Court’s legal reasoning can be dissected into several key components:

• Patent Sufficiency: The Court adopted a two-stage approach from Regeneron v Genentech, first assessing plausibility and then undue burden. For Family A patents, the claims were deemed implausible as they broadly covered a vast chemical space without credible support that substantially all claimed compounds would exhibit the therapeutic effect.
• Claim Construction: The Court emphasized the correct interpretation of claims with structural and functional limitations. It rejected the lower court’s overly broad interpretation that implied an implicit promise that all structurally claimed compounds would be efficacious.
• Functional Limitations: The Court clarified that functional features (e.g., HIF-PH inhibition) in claims do not require identification of all possible compounds but necessitate that a skilled person can identify some with the desired function without undue effort.
• Obviousness: For Family B patents, the Court found that using HIF-PH inhibitors to treat ACD was obvious in light of prior art (WO 997), which already suggested using these compounds for various anemia-related conditions, thereby rendering the patents obvious and invalid.

A significant point of contention was the interpretation of obligatory identification of all claimed compounds versus the necessity to identify some without undue burden. The Court sided with the latter, aligning with established EPC (European Patent Convention) principles and rejecting the lower court’s broader approach influenced by German jurisprudence.

Impact

This judgment has profound implications for pharmaceutical patenting, particularly in the realm of biochemical inventions:

• Refined Criteria for Sufficiency: The decision reinforces a balanced approach to patent sufficiency, ensuring that claims are not excessively broad while allowing functional language when adequately supported.
• Guidance on Functional and Structural Claims: By clarifying the interpretation of claims combining structural and functional features, the judgment aids patent drafters in crafting robust claims that withstand validity challenges.
• Impact on Future Obviousness Assessments: Upholding the invalidity of Family B patents underscores the critical examination of prior art and discourages overly broad claims that encompass obvious extensions of existing therapeutic uses.
• Promotes Transparent Disclosure: The emphasis on linking claims to concrete embodiments in the specification encourages patentees to provide comprehensive disclosure to support broad yet valid claims.

Complex Concepts Simplified

Conclusion

The Court of Appeal's decision in FibroGen Inc v. Akebia Therapeutics Inc serves as a critical benchmark in the judiciary’s approach to patent sufficiency and obviousness within the pharmaceutical sector. By affirming the invalidity of Family A patents due to insufficiency and upholding the invalidity of Family B patents based on obviousness, the Court has delineated clear boundaries for future patent claims.

The judgment underscores the necessity for patentees to ensure that their patents are neither overly broad nor inadequately disclosed. Claims integrating both structural and functional features must be supported by sufficient evidence that a skilled person can identify at least some compounds within the claimed scope that achieve the desired function without undue burden.

Furthermore, the dismissal of the appeal concerning the obviousness of Family B patents reiterates the importance of thoroughly evaluating prior art and avoiding claims that extend beyond what is non-obvious. This decision will undoubtedly influence future patent strategies, encouraging a more precise and evidence-backed approach to claim drafting in the biochemical and pharmaceutical industries.

Ultimately, this judgment reinforces the balance between rewarding genuine innovation and preventing the monopolization of obvious extensions of existing knowledge, thereby fostering an equitable environment for both patentees and competitors in the biomedical field.