Introduction

FibroGen Inc v. Akebia Therapeutics Inc ([2021] EWCA Civ 1279) represents a significant case in the realm of intellectual property law, particularly concerning patent sufficiency and claim construction within the biotechnological sector. The dispute primarily revolves around the validity and infringement of six patents owned by FibroGen Inc and exclusively licensed to Astellas Pharma Inc, pertaining to the use of HIF-PH inhibitors for treating anemia, specifically Chronic Kidney Disease (CKD) anemia and Anaemia of Chronic Disease (ACD).

The Court of Appeal (Civil Division) of England and Wales examined critical issues of patent sufficiency, claim construction, and obviousness. This commentary delves into the intricacies of the judgment, exploring the court's reasoning, the precedents cited, and the broader implications for future patent litigations in the pharmaceutical and biotechnological industries.

Summary of the Judgment

The Court of Appeal upheld the High Court's decision to invalidate the patents on two primary grounds:

• Family A Patents: Initially challenged for insufficiency, these patents were deemed invalid because the claims were excessively broad and lacked plausibility across their entire scope. The court found that FibroGen failed to adequately demonstrate that the wide range of compounds claimed would effectively inhibit HIF-PH and treat CKD anemia without imposing an undue burden on the skilled team.
• Family B Patents: These were invalidated for obviousness over prior art (WO 997). The court determined that it was obvious for a skilled team to utilize the disclosed HIF-PH inhibitors for treating ACD, given the teachings of WO 997 and the common general knowledge at the time.

On appeal, FibroGen successfully contested the invalidation of the Family A patents, thereby reinstating their validity and finding them to be infringed by Akebia's product, vadadustat. However, the Court dismissed the appeal concerning the obviousness of the Family B patents and the respondent's notice regarding infringement of Formula I by vadadustat.

Analysis

Precedents Cited

The judgment extensively referenced critical precedents that have shaped the current understanding of patent sufficiency and obviousness:

• Regeneron v Genentech: Established a two-stage approach for assessing insufficiency, focusing on plausibility and undue burden.
• Biogen Inc. v Medeva plc: Highlighted the necessity of a clear technical contribution in patent claims.
• Idenix v Gilead: Emphasized that validity is to be judged by the claims themselves, not by limiting the technical contribution post hoc.
• Dipeptidyl-Peptidase-Inhibitoren X ZB 8/12: A German Supreme Court case influential in the discussion on functional claim limitations and insufficiency.
• Unwired Planet v Huawei: Provided insights into the distinction between claim ambiguity and conceptual uncertainty.
• Actavis v ICOS: Discussed the improper use of stepwise analysis in determining obviousness and the concept of expectation of success.

Legal Reasoning

The Court's legal reasoning centered on the interpretation of patent claims with both structural and functional features. A pivotal aspect was the distinction between defining compounds solely by their structure versus incorporating functional limitations, such as their biochemical activity.

For the Family A patents, the court employed a two-step approach to assess insufficiency:

1. Plausibility: Determined whether it was reasonable to expect that the claimed broad class of compounds would exhibit the desired therapeutic effect.
2. Undue Burden: Assessed whether carrying out the invention across the entire scope of the claim would impose an excessive amount of work on the skilled team.

The initial judgment found that the breadth of the claims in Family A patents went beyond what was plausibly supported by the evidence, leading to an insufficiency verdict. However, upon appeal, FibroGen successfully argued that the court misconstrued the claim construction and improperly applied the standard for sufficiency, thereby reinstating the validity of the Family A patents.

In contrast, the Family B patents were declared obvious over WO 997 due to the explicit suggestion in the prior art to use HIF-PH inhibitors for treating ACD. The court determined that the skilled team would have found it obvious to explore this avenue, making the Family B patents invalid.

Impact

This judgment has profound implications for future patent applications and litigations, especially in the biotechnological and pharmaceutical fields where claims often encompass broad classes of compounds with specific functional activities. Key impacts include:

• Enhanced Scrutiny on Claim Breadth: Patent claims must strike a balance between breadth and sufficiency, ensuring that broad claims are adequately supported by the disclosed invention.
• Clarification on Functional Limitations: The court reaffirmed that functional features cannot unreasonably extend the scope of patent claims, and sufficient evidence must support the claimed utility of such functional groups.
• Influence on Biotech Patent Drafting: Patent drafters must ensure that claims with both structural and functional definitions are meticulously supported by the specification to withstand scrutiny on sufficiency grounds.
• Obviousness Evaluations: Reinforces the necessity for patent applicants to demonstrate non-obviousness, especially when prior art suggests similar utility or functionality.

Complex Concepts Simplified

Patent Sufficiency

Patent sufficiency refers to the requirement that a patent must fully disclose the invention so that a person skilled in the relevant field can carry it out without undue experimentation. In this case, the issue was whether the broad class of compounds claimed by FibroGen was sufficiently supported by the evidence to treat CKD anemia.

Functional Claim Limitations

When patent claims include functional limitations—i.e., they define a compound not just by its structure but also by its biochemical activity—the disclosure must adequately support that functionality across the entire scope of the claim. Failure to do so can render a patent invalid for insufficiency.

Plausibility and Undue Burden

• Plausibility: For a broad claim to be plausible, there must be a reasonable expectation that the claimed invention works as described, based on the evidence provided.
• Undue Burden: This assesses whether carrying out the invention across the entire claim would require excessive effort from a skilled team, making the claims overly broad.

Markush Structure

A Markush structure is a way of defining a class of chemical compounds in patent claims by outlining a general structure with variable substituents. This allows the claim to cover a wide variety of specific compounds within the defined class.

Obviousness

Obviousness is a ground for patent invalidity where the claimed invention would have been obvious to a person skilled in the art at the time of the patent, based on existing knowledge and prior art. In this case, the Family B patents were deemed obvious because the prior art suggested using HIF-PH inhibitors for treating ACD.

Conclusion

The FibroGen v. Akebia judgment underscores the delicate balance patent claims must maintain between breadth and sufficiency. By overturning the invalidation for Family A patents, the Court of Appeal reaffirmed that claims encompassing broad classes of compounds with specific functional activities can be valid, provided they are sufficiently supported by the evidence. Conversely, the invalidation of Family B patents for obviousness serves as a cautionary tale for patent applicants to ensure that their inventions are not only novel but also non-obvious in the context of existing knowledge.

This case reinforces the necessity for meticulous claim drafting and comprehensive disclosure in patent applications, especially within highly technical and competitive fields like biotechnology and pharmaceuticals. Moving forward, patent drafters and legal professionals must heed the precedents set by FibroGen v. Akebia to navigate the complexities of patent law effectively.