Background
Biogen holds the approved drug Tecfidera® (dimethyl fumarate, or DMF), an oral treatment for relapsing forms of multiple sclerosis. When Biogen sought FDA approval for Tecfidera, the active ingredient listed in the NDA was DMF. Under the Hatch-Waxman Act, a patent covering an FDA-approved drug can be extended—by up to five years—to compensate for time lost during the regulatory review process. Biogen received a patent term extension of 811 days on its patent covering methods of treating multiple sclerosis with DMF.
Banner Life Sciences sought to sell a generic version of Tecfidera. The key dispute was whether Biogen’s extended patent covered methods involving monomethyl fumarate (MMF). When patients take DMF, their bodies rapidly metabolize it: the DMF molecule loses one of its methyl ester groups and becomes MMF, which is the compound that ultimately reaches the pharmacological site of action in the body. Biogen’s patent claims covered methods of treatment using either DMF or MMF. Banner argued that the patent term extension could only protect the FDA-approved active ingredient (DMF) and its salts and esters—not a metabolite like MMF. Biogen argued that MMF, as the biologically active form of the drug, should also be covered.
The Court’s Holding
The Federal Circuit affirmed the district court and ruled for Banner. Writing for a unanimous panel, Judge Reyna held that the scope of a patent term extension under 35 U.S.C. § 156(b)(2) is strictly limited to what the statute specifies: the active ingredient of the approved product as defined in § 156(f), including salts and esters of that active ingredient, but nothing beyond.
The court concluded that MMF is neither the active ingredient approved by the FDA (which was DMF), nor a salt or ester of DMF. MMF is a metabolite—a compound produced by the body’s own enzymatic processing of DMF after it is administered. The statute’s reference to “any ester” covers DMF’s esterified forms, but de-esterification—which is what happens when DMF converts to MMF in the body—produces the opposite result: it breaks down the ester, it does not form one. Because the statute does not extend patent term protection to metabolites of the active ingredient, the MMF-directed claims of Biogen’s patent were not protected by the extension, and Banner could seek to market its generic without infringing those claims.
Key Takeaways
- Patent term extensions under Hatch-Waxman § 156 are tied strictly to the active ingredient approved by the FDA as specified in the NDA—including its salts and esters—but do not reach metabolites of that ingredient formed in the body.
- Pharmaceutical companies cannot bootstrap claims covering a drug’s metabolites into the scope of a patent term extension simply because the metabolite is the biologically active form of the drug; the statutory coverage is limited to what was actually approved.
- When structuring patent portfolios for Hatch-Waxman drugs, companies should consider filing patents specifically on active metabolites (e.g., MMF itself) as separate compounds or methods, rather than relying on an extension of the parent active ingredient to protect metabolite claims.
- Generic manufacturers facing a patent term extension should analyze whether the patentee’s claims extend beyond the specific active ingredient and its salts/esters—metabolite claims may not be within the extension’s scope.
Why It Matters
Tecfidera was a blockbuster drug generating billions of dollars in annual revenue for Biogen. The patent term extension was intended to give Biogen additional exclusive market time to compensate for years spent in FDA review. This decision significantly narrowed that protection: by holding that the extension did not cover MMF-based claims, the Federal Circuit effectively cleared a path for generic entry on at least some of Biogen’s claims earlier than Biogen had anticipated.
More broadly, the ruling provides a clear rule for the pharmaceutical industry: the Hatch-Waxman patent term extension system is designed to protect exactly what the FDA approved—the specific approved active ingredient and its chemically related forms (salts and esters)—not the full pharmacological lifecycle of that ingredient in the human body. Drug innovators who want to protect metabolites must seek and obtain separate patents on the metabolites themselves, not rely on extensions of the parent compound’s patent to do that work.