Background
Amgen held patents on a class of antibodies that bind to a specific portion (epitope) of the PCSK9 protein and block PCSK9’s interaction with LDL receptors — a mechanism that lowers LDL cholesterol levels. The claimed class (genus) included all antibodies that (1) bind to specific residues on the PCSK9 protein and (2) block PCSK9 from binding to LDL receptors. Amgen’s marketed antibody Repatha® (evolocumab) was one such antibody. Sanofi and Regeneron marketed a competing antibody Praluent® (alirocumab), which also binds to PCSK9 in the same epitope region.
Amgen sued for infringement. Sanofi and Regeneron challenged the patents as lacking adequate enablement under § 112(a) — arguing that the patents did not enable persons of ordinary skill to make and use the full scope of the claimed antibody genus without undue experimentation. There are millions of possible antibodies that could potentially bind to the claimed PCSK9 epitope region; Amgen had only exemplified a relative handful.
The Court’s Holding
The Federal Circuit affirmed invalidity for lack of enablement. Applying the Wands factors for evaluating whether enablement requires undue experimentation, the court found that the scope of the claimed genus — potentially millions of antibodies with the specified functional properties — vastly exceeded the scope of what Amgen had actually enabled through its exemplified antibodies and disclosed screening methods. While Amgen disclosed two approaches for identifying antibodies in the claimed class (a roadmap approach and a conservative substitution approach), those methods required extensive trial-and-error experimentation to arrive at new working antibodies in the genus.
The court rejected Amgen’s argument that it only needed to enable “representative species” of the claimed genus. When the claimed genus is defined by function (binding to a specific epitope and blocking a specific interaction) and not by structure, the enablement requirement scales with the breadth of the functional claim — a genus claim covering all antibodies with specified functions requires enabling the full scope, not just representative examples.
Key Takeaways
- Functional genus claims for antibodies — claiming all antibodies that bind to a specific epitope or perform a specific function — face heightened enablement requirements when the genus is extremely broad and structurally undefined: disclosing a handful of exemplary antibodies does not enable the full genus.
- The Wands factors for undue experimentation analysis apply to antibody genus patents by scaling the enablement burden with the breadth of the claim — broader functional genera require more enablement, not less.
- Antibody patent strategy post-Amgen v. Sanofi must balance claim breadth against enablement: narrower claims directed to specific antibodies or antibodies with specific structural features are more likely to be adequately enabled than claims covering all antibodies with a specified binding function.
- This Federal Circuit decision previewed the Supreme Court’s subsequent 2023 affirmance, which resolved the case definitively in favor of robust enablement requirements for broadly functional antibody claims — one of the most significant patent law developments in the biopharmaceutical sector.
Why It Matters
Amgen v. Sanofi at the Federal Circuit (2021) was the precursor to the Supreme Court’s landmark 2023 decision on the same patents — a case that ultimately became one of the most significant biopharmaceutical patent decisions of the decade. The Federal Circuit’s 2021 decision established the enablement framework that the Supreme Court subsequently affirmed and clarified: when a patent claims a broad functional genus, the scope of the claim must be commensurate with the scope of the enablement, regardless of the patent holder’s pioneering status in the field.
For the biopharmaceutical industry — where antibody drug development is a dominant modality and genus claims are a primary patent protection strategy — the Amgen v. Sanofi line of cases forced a fundamental reconsideration of antibody claim drafting. The decisions signaled that functional genus claims covering all antibodies that achieve a specified therapeutic mechanism are at serious risk of enablement invalidity when the structural diversity of the claimed genus far exceeds what the patent actually teaches, regardless of the commercial importance of the invention.