In a pivotal decision (3 Ni 6/24 (EP)), the German Federal Patent Court (BPatG) invalidated a patent for a cancer therapy due to a “structural paradox” that highlights the strict requirements of patent enablement.

The Case: Linear vs. Angular TIC10 The patent claimed a pharmaceutical composition using compound NSC350625 (also known as TIC10) for cancer treatment. Crucially, the patent text lacked a structural formula or chemical name, referring only to the NCI database identifier.

• The Conflict: At the priority date (2011), public databases (PubChem) associated this ID with a linear tricyclic structure. It was only in 2014 that researchers discovered the actual physical substance deposited under that ID had an angular structure
• The Problem: Only the angular isomer is biologically active against cancer; the linear structure described by the state of the art in 2011 is ineffective.

The Court’s Deep Dive into Enablement The court declared the patent void for lack of enablement (Art. 83 EPC / § 34 Abs. 4 PatG). The ruling provides a masterclass on the limits of “disclosure surrogates” in chemical patents:

1. No Deposit Surrogates for Small Molecules: The court clarified that while biological materials can be “disclosed” via a deposit (§ 34 Abs. 8 PatG), this does not apply to small molecules. Small molecules must be characterized by a chemical name or structural formula within the written description. Since a small molecule can always be described in writing, a physical deposit cannot substitute for a missing structural definition.
2. The “Written Truth” of the Priority Date: Enablement must exist at the filing or priority date. If the “written truth” (the information available to a skilled person at that time) points to an inactive structure, the patent is not enabled. A later correction of a database entry cannot retroactively fix an insufficient original disclosure.
3. Technical Usefulness (Brauchbarkeit): Under German law, an invention is only enabled if it is “technically useful”. If a person skilled in the art follows the patent’s instructions and synthesizes the compound associated with the database ID at that time, they obtain an inactive substance. Because this fails to solve the technical problem, the invention is considered “mere speculation” and lacks the required disclosure.
4. The Barrier of Commercial Availability: The patent holder argued the compound was “available” via the NCI repository. The court rejected this, stating that for a compound to be considered “available” to the public, it must be an approved drug or a standard product in chemical catalogs at the priority date. Restricted access (e.g., no export outside the USA) or a lack of quality guarantee for repository samples does not satisfy the requirement of public availability.

Practical Guidance for Patent Practitioners (Derived from 3 Ni 6/24)

Based on the court’s reasoning, here are essential takeaways for drafting and defending chemical and pharmaceutical patents:

• Structural Formulas are Essential: Never rely solely on database IDs (NSC, CAS, PubChem) or trivial names like “TIC10”. Always include the IUPAC name and the complete structural formula in the original application.
• Verify Database Accuracy at the Priority Date: Before filing, double-check that the structural information in public databases for your compound is correct. If the database is wrong on your filing day, your patent may be tied to that error forever, potentially leading to a lack of enablement.
• The Deposit Trap: Do not treat small molecules like biological inventions. A physical deposit of a chemical substance does not satisfy the disclosure requirement if the written description is missing or incorrect.
• Address Isomerism Explicitly: If a specific isomer (e.g., angular vs. linear) is responsible for the effect, ensure the patent explicitly identifies that specific structure.
• Supply Beware of Limited Chains: Referencing a compound by its source (like the NCI) is only sufficient if the compound is truly commercially available without restrictions. If a skilled person cannot easily buy the substance in their own country (e.g., Germany) at the priority date, the disclosure may be deemed insufficient.
• Ensure “Technical Usefulness”: Ensure your application contains enough data to show that the specific structure you are claiming actually achieves the stated therapeutic effect. If the described path leads to an inactive compound, the patent is at risk.