Background
Amgen developed evolocumab (Repatha), a monoclonal antibody that inhibits PCSK9 — a protein that degrades LDL receptors and thereby raises “bad” cholesterol levels. By blocking PCSK9, the antibody allows LDL receptors to function normally and reduce circulating LDL. Sanofi developed a competing antibody, alirocumab (Praluent), that also inhibits PCSK9 but does so by binding to different amino acid residues. Amgen sued Sanofi for infringement of two patents that claimed broad functional genera of anti-PCSK9 antibodies — essentially covering all antibodies that (1) bind to specific residues on PCSK9 and (2) block PCSK9 from binding to LDL receptors.
Amgen’s patents disclosed 26 specific antibody amino acid sequences and described two methods — a “roadmap” and a “conservative substitution” approach — for making other antibodies that perform the claimed function. Sanofi challenged the patents as invalid for lack of enablement under 35 U.S.C. § 112(a). After two trials, the district court granted judgment as a matter of law that the claims were not enabled. Amgen appealed.
The Court’s Holding
The Federal Circuit affirmed. Judge Lourie, writing for a unanimous panel, applied the Wands factors — the framework courts use to assess whether undue experimentation is required to practice the full scope of a claim. The court agreed that Amgen’s claimed genus was vast: there are potentially millions of antibodies capable of binding to the specified PCSK9 residues, and antibody science is a notoriously unpredictable field in which a small change in amino acid sequence can dramatically alter binding properties. Identifying which members of such a large, unpredictable genus would perform the claimed function without degrading other important properties would require extensive, open-ended experimentation.
The court found that the 26 disclosed examples were an insufficient window into the claimed genus, and Amgen’s two “methods” for making additional antibodies were essentially instructions to “trial and error” rather than guided procedures. Because a person of ordinary skill in the art would need to undertake undue experimentation to practice the full scope of the claims, the enablement requirement was not met. The court noted that to satisfy enablement, a patentee claiming a functional genus must provide adequate instruction over the full scope of what is claimed, not just teach how to make a handful of representative embodiments.
Key Takeaways
- Broad functional genus claims in the antibody space require enablement across the full scope of the claimed genus; disclosing 26 specific examples was insufficient where the genus potentially included millions of candidates in an unpredictable field.
- The Wands factors, particularly the unpredictability of the art and the breadth of the claims, weigh heavily against enablement when a patent claims any molecule that performs a function without providing structural guidance about how to identify members of that class.
- Instructions that amount to “try-this-approach-and-see” do not constitute enabling disclosure — a specification must provide a genuine roadmap, not a research assignment.
- This decision, later affirmed by the Supreme Court in 2023, fundamentally reshaped how biotech companies draft antibody and biologics patents.
Why It Matters
Amgen v. Sanofi is one of the most consequential biologics patent cases in decades. At stake was the concept of “genus claiming” in antibody patents — the practice of claiming all antibodies that bind a target or perform a function, rather than specific antibodies defined by their amino acid sequences. Genus claiming had long been a cornerstone of biotech patent strategy because it allowed a first inventor to obtain broad protection covering competitors’ variations, not just the specific molecules the inventor characterized.
The Federal Circuit’s decision — affirmed unanimously by the Supreme Court in Amgen Inc. v. Sanofi (2023) — made such broad claims extremely difficult to sustain. Companies must now disclose and enable a representative set of specific examples that genuinely reflects the full breadth of the claimed genus, or accept that competitors’ antibody variations will fall outside their patent’s reach. The practical effect has been a significant shift in how antibody patents are drafted and prosecuted, with greater emphasis on structural disclosure rather than pure functional claiming.