Gavel striking a DNA strand, symbolizing biotech patent challenges.

Patent Review Standards: What Merck v. Gnosis Means for Biotech Innovation

Reese Marlowe in Law & Justice December 2025 • 4 min read.

"A closer look at how the Supreme Court's decision impacts inter partes review and the future of pharmaceutical patents."

In the ever-evolving world of pharmaceutical patents, the U.S. Supreme Court's decision in Merck & Cie v. Gnosis S.p.A. has set a new course for inter partes review (IPR) proceedings. On October 11, 2016, the Supreme Court declined to hear Merck's appeal, solidifying the application of a deferential "substantial evidence" standard for reviewing obviousness determinations made by the U.S. Patent Trial and Appeal Board (PTAB). This decision has significant implications for companies seeking to challenge or defend patents through the IPR process.

The case revolved around Merck's U.S. Patent No. 6,011,040, which covers the use of tetrahydrofolates in natural stereoisomeric form to regulate homocysteine levels—a critical factor in cardiovascular, ocular, neurological, and skeletal health. Gnosis challenged the patent, arguing that its claims were obvious based on prior art. The PTAB sided with Gnosis, a decision that Merck appealed, leading to the Supreme Court's involvement.

This article delves into the details of the Merck v. Gnosis case, tracing the arguments presented before the PTAB, the Federal Circuit, and ultimately the Supreme Court. By examining the facts, legal arguments, and implications of this decision, we aim to provide clarity on the current standard of review for IPR proceedings and what it means for future patent disputes in the biotech industry.

The Heart of the Matter: Unpacking the Patent Dispute

Gavel striking a DNA strand, symbolizing biotech patent challenges.

At the core of the Merck v. Gnosis dispute was U.S. Patent No. 6,011,040, which focuses on using tetrahydrofolates to manage homocysteine levels in the human body. Elevated homocysteine levels are associated with various diseases, making the methods described in the patent potentially valuable for treating and preventing these conditions.

Gnosis initiated an IPR of claims 1–3, 5, 6, 8, 9, 11-15, and 19-22 of the '040 patent, asserting that these claims were obvious. The challenge hinged on the argument that the methods described in the patent were already known or suggested by existing prior art. Claim 2, from which all the challenged claims depend, is central to understanding the dispute:

"2. A method of preventing or treating disease associated with increased levels of homocy[s]teine levels in the human body comprising administering at least one tetrahydrofolate in natural stereoisomeric form to a human subject."

Gnosis specifically targeted claim 11, which relates to a method where increased homocysteine levels are associated with methylene tetrahydrofolate reductase deficiency, using 5-methyl-(6S)-tetrahydrofolic acid. Gnosis contended that this claim was obvious based on the combination of three key references: Serfontein, Marazza, and Ubbink. The core argument was that these references, when combined, disclosed or suggested all the elements of claim 11, making it an obvious variation.

The Broader Impact: Navigating the New Landscape of Patent Reviews

The Supreme Court’s decision to deny certiorari in Merck v. Gnosis underscores the importance of thorough preparation and robust evidence when litigating patent validity before the PTAB. With the “substantial evidence” standard firmly in place, challengers face a higher hurdle in appealing PTAB decisions. For those in the biotech and pharmaceutical sectors, understanding these nuances is now more critical than ever. As the legal landscape continues to evolve, staying informed and strategically adapting to these changes will be paramount for protecting and challenging intellectual property rights.

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Everything You Need To Know

What was the main focus of the patent dispute in the Merck v. Gnosis case?

The case of Merck & Cie v. Gnosis S.p.A. centered on U.S. Patent No. 6,011,040. This patent covered the use of tetrahydrofolates, in their natural stereoisomeric form, to regulate homocysteine levels in the human body. High homocysteine levels are linked to various health issues, making this method of management potentially valuable. Gnosis challenged this patent through an inter partes review (IPR) process, arguing that the patent claims were obvious given existing prior art.

How did the Supreme Court's decision in Merck v. Gnosis impact patent review standards?

The Supreme Court's decision in Merck & Cie v. Gnosis S.p.A. established the application of a 'substantial evidence' standard for reviewing obviousness determinations made by the U.S. Patent Trial and Appeal Board (PTAB) during Inter Partes Review (IPR) proceedings. This means that when the PTAB makes a decision on patent validity, the courts will defer to that decision if it is supported by substantial evidence. This standard makes it more challenging for parties to successfully appeal PTAB rulings, increasing the burden on those challenging a patent's validity.

What specific claims of the patent were challenged in the Merck v. Gnosis case and why?

The patent at the heart of the dispute, U.S. Patent No. 6,011,040, focused on the use of tetrahydrofolates to manage homocysteine levels. Claim 11 of the patent, related to a method for treating conditions associated with increased homocysteine levels, was specifically challenged by Gnosis. Gnosis argued this claim was obvious based on a combination of prior art references. This reveals how critical the precise wording of patent claims is and how prior art can be used to challenge these claims.

What is the role of Inter Partes Review (IPR) in the context of this case?

The Inter Partes Review (IPR) process, used by Gnosis to challenge Merck's patent, is a legal procedure before the U.S. Patent Trial and Appeal Board (PTAB). It allows third parties to challenge the validity of an issued patent based on prior art. The Merck v. Gnosis case highlights the importance of IPRs in the biotech industry, influencing how patent validity is assessed and litigated. The Supreme Court's decision directly impacts how these reviews are conducted and how easily decisions can be overturned.

What does the Merck v. Gnosis decision mean for the future of biotech innovation and patent disputes?

The implications of the Merck v. Gnosis case are significant for the biotech industry. With the Supreme Court upholding the 'substantial evidence' standard, challengers of patents face a higher bar in the IPR process. Companies must now prepare more thoroughly, gathering robust evidence to support their positions before the PTAB. This also means that those defending patents will find their patents more secure, as it is more difficult to overturn decisions. The legal landscape for biotech patents is changing, requiring strategic adaptability to protect and challenge intellectual property rights effectively.