July 2026 Overview
Broad antibody claims have faced a difficult path in the US since Amgen v Sanofi, particularly where the claim covers a large functional genus.
The Federal Circuit’s decision in Teva v Eli Lilly is therefore interesting because the court drew an important distinction: claims to antibodies themselves are not necessarily treated the same way as claims to methods of treatment using a known class of antibodies.
Case Summary
The case concerned Teva patents for treating headache using humanised anti-CGRP antagonist antibodies. Eli Lilly argued that the claims were invalid for lack of written description and enablement because the specification failed to disclose a representative number of species of the claimed genus of humanised anti-CGRP antagonist antibodies, noting that only one humanised version was disclosed.
Following Amgen v Sanofi, it was expected that such an attack would likely succeed.
However, the Federal Circuit disagreed and accepted that anti-CGRP antibodies were already known, that humanisation could be viewed as routine, and that the skilled person would understand the antibodies to work in the claimed method. This appears to be a departure from the Federal Circuit’s usual view with respect to written description and antibody genus claims.
Turning to enablement, Eli Lilly argued that the claims were not enabled because of the very large number of possible candidate antibodies defined by the claim. As such, Eli Lilly argued, the specification left the skilled artisan with a “research assignment” of screening and testing candidates to determine which antagonise CGRP, amounting to undue experimentation.
The Federal Circuit rejected this argument and notably distinguished the case from Amgen v Sanofi and Idenix v Gilead. The Federal Circuit’s reasoning once again hinged on the fact that the claims were not to the antibodies themselves, but to methods of treating headache.
Take home Message
Amgen v Sanofi may not apply with the same force where the invention is framed as a method of treatment using a known antibody genus, rather than as a claim to the antibody itself.
The decision also highlights an interesting contrast with Europe. The EPO has often been more comfortable with broad antibody claims where suitable screening assays are available, while the US has generally taken a stricter approach to enablement and written description.
That said, the Federal Circuit’s reliance on routine antibody generation and humanisation signals a potential shift by the US in a more European-like direction.
