Background
Enzo Biochem held U.S. Patent 4,900,659, covering nucleic acid probes designed to detect the bacteria that causes gonorrhea, Neisseria gonorrhoeae, while avoiding false positives from the closely related Neisseria meningitidis. The probes worked by hybridizing selectively to the target bacteria’s DNA at a ratio of at least approximately 5:1 over the related bacteria. Enzo’s inventors had identified three specific probe sequences and deposited samples of the sequences at the American Type Culture Collection (ATCC), a public biological repository.
Enzo sued Gen-Probe and other diagnostic companies for patent infringement. The defendants moved for summary judgment of invalidity, arguing that the patent’s written description failed to adequately describe the claimed probes — the specification described the probes primarily by their functional properties (selective hybridization) rather than by their chemical structures. The district court agreed and invalidated the claims. An initial Federal Circuit panel affirmed, holding categorically that biological deposits could not satisfy the written description requirement.
On rehearing, the panel revisited its original ruling and issued a revised decision that became one of the most significant biotechnology patent opinions of its era.
The Court’s Holding
The revised Federal Circuit panel reversed the district court and held that a patent specification’s reference to a deposit in a public repository such as the ATCC can constitute adequate written description of the deposited material. The court reasoned that the written description requirement’s core purpose — giving the public access to the disclosed invention — is satisfied when the biological material is made accessible in a recognized public depository that anyone can access.
More broadly, the court adopted a flexible standard for written description: an inventor can satisfy the requirement by disclosing “sufficiently detailed, relevant identifying characteristics” of the claimed subject matter, which may include functional characteristics “when coupled with a known or disclosed correlation between function and structure.” The court rejected the rigid view that only structural, sequence-level descriptions could ever suffice in biotechnology cases.
Judges Rader and Linn dissented, arguing that the majority was conflating the written description requirement with the enablement requirement, and that written description should require actual disclosure of structural identity. Their dissent foreshadowed ongoing Federal Circuit debates about the scope and independent purpose of written description, which the court revisited en banc in Ariad Pharmaceuticals v. Eli Lilly (2010).
Key Takeaways
- Patent specifications may satisfy the written description requirement by referencing biological material deposited in a publicly accessible repository like the ATCC.
- Functional descriptions can satisfy written description when paired with a disclosed correlation between the function and the underlying structure.
- The written description requirement is flexible in biotechnology: inventors need not always provide full chemical structures if other means of identification are adequate.
- Biological deposits serve a disclosure function equivalent to written structural description for purposes of § 112.
- The case highlighted the unresolved tension between written description as a priority-policing tool versus as an independent disclosure requirement.
Why It Matters
Enzo Biochem was a lifeline for biotechnology patent holders. Before the ruling, the original panel decision had threatened to invalidate a wide swath of biotech patents that relied on ATCC deposits — a standard practice in the industry when inventors cannot fully describe complex biological sequences in written form. By confirming that deposits satisfy written description, the court preserved the validity of patents on nucleic acid probes, cell lines, microorganisms, and other materials that had been publicly deposited but not fully characterized in writing.
The case also injected lasting uncertainty into the written description doctrine, particularly for genus claims in biotechnology. The dissent’s critique resonated with the Federal Circuit’s later en banc decision in Ariad v. Eli Lilly (2010), which confirmed that written description is an independent requirement from enablement. For biotech and pharmaceutical patent practitioners, Enzo Biochem remains a foundational case on how biological inventions must be disclosed in patent specifications.