Background
Biogen International GmbH held U.S. Patent No. 8,399,514, which claimed a method of treating multiple sclerosis (MS) by administering a therapeutically effective amount of approximately 480 mg per day of dimethyl fumarate (DMF), the active ingredient in the blockbuster MS drug Tecfidera. Mylan Pharmaceuticals filed an Abbreviated New Drug Application (ANDA) seeking FDA approval to market a generic version of Tecfidera, triggering Hatch-Waxman patent litigation.
The district court found the ‘514 patent invalid for failing to satisfy the written description requirement of 35 U.S.C. § 112(a). The critical issue was that the specification’s only reference to a 480 mg/day dose appeared as one value in a broad dosage range table, without any clinical data, efficacy evidence, or narrative explanation indicating that the inventors believed that specific dose was therapeutically effective for MS. Biogen appealed, arguing the disclosure was sufficient to establish the inventors’ possession of the claimed invention.
The Court’s Holding
The Federal Circuit affirmed in a 2-1 decision. The majority, written by Judge Reyna and joined by Judge Hughes, held that the district court did not clearly err in finding that a person of ordinary skill in the art would not have recognized from the specification that the inventors had actually conceived of — and thus possessed — a therapeutically effective 480 mg/day dose for treating MS. The specification’s single mention of that dose, buried within a wide dosage range and unaccompanied by any clinical or efficacy data specifically tied to that dose, was insufficient to demonstrate possession of the invention as claimed.
The majority emphasized that the written description requirement is not a question of what a skilled artisan could figure out from a disclosure but whether the specification itself demonstrates that the inventors actually had the claimed invention in hand at the time of filing. Judge O’Malley dissented vigorously, arguing that the specification expressly stated that 480 mg per day was an effective amount and that the majority was conflating the enablement and written description analyses by effectively requiring clinical proof of efficacy in the specification — a standard the written description requirement does not impose.
Key Takeaways
- A single incidental mention of a specific dosage in the context of a broad numerical range may be insufficient to establish written description for a claim specifically directed to that dosage, even if a skilled artisan could understand the reference.
- The written description standard asks whether the specification demonstrates the inventors’ actual possession of the specific invention claimed — not whether a skilled artisan could have predicted that the claimed embodiment would work.
- Pharmaceutical patent applicants should include specific clinical data, efficacy evidence, or at minimum a clear narrative tying a specific dosage to a therapeutic effect, rather than relying on a broad dosage range that happens to include the claimed value.
- The 2-1 split and the strong dissent, combined with the subsequent denial of en banc rehearing over further dissents, reflect ongoing uncertainty about how strictly the written description standard applies to pharma dose-ranging patents.
Why It Matters
Biogen v. Mylan had substantial commercial stakes — Tecfidera was generating billions of dollars in annual revenue, and the written description finding opened the door for generic competition. More broadly, the decision raised alarms across the pharmaceutical industry about the adequacy of conventional patent prosecution practices for dosage-related claims. If a specification merely lists a dose range without clinical validation of each point in that range, a later claim narrowed to a specific dose may be vulnerable to written description invalidity.
The split panel and the near-deadlock at en banc rehearing highlighted a genuine doctrinal tension: the majority approach risks conflating written description with enablement by demanding something close to proof of efficacy, while the dissent’s approach may allow patentees to claim specific dosages based on little more than a passing mention. For drug companies, the practical lesson is clear: at the time of filing, document the inventors’ actual possession of the specific claimed dosages with clinical or experimental data, and make that documentation prominent in the specification.