Federal Circuit Updates Pharma Method-of-Use Patent Guidance
Recent Federal Circuit rulings refine standards for pharmaceutical method-of-use patent claims.
Why it matters: Pharma patent litigation protects drug innovations and market exclusivity. These Federal Circuit decisions influence how in-house counsel and firms draft and defend method-of-use claims for known compounds.
- In Teva v. Eli Lilly (Apr 16, 2026), the Federal Circuit reversed invalidity for claims on anti-CGRP antibodies treating headaches.
- The court held that a well-known composition genus can satisfy written description without disclosing every genus member.
- In In re Xencor (Mar 13, 2025), broad treatment claims lacking disease or patient specificity failed written-description requirements.
- Method-of-treatment claims may now survive invalidity challenges if the antibody genus and its class effect are well established.
The Federal Circuit's recent decisions in Teva Pharmaceuticals International GmbH v. Eli Lilly & Co. and In re Xencor, Inc. provide valuable guidance on written description and enablement standards for pharmaceutical method-of-use (MOT) patent claims.
In Teva v. Eli Lilly, the court reversed a judgment of invalidity for claims directed to reducing headache incidence using humanized anti-CGRP antagonist antibodies. The key takeaway is that when a composition genus is well-known to persons skilled in the art, the patent need not exhaustively disclose every genus member to satisfy written description and enablement requirements. As explained by legal experts, "specificity in claiming and evidentiary rigor in establishing POSA knowledge are the twin pillars of valid method-of-use claims for known compounds." (Antoinette F. Konski)
Contrastingly, In re Xencor affirmed a written-description rejection where claims broadly recited "treating a patient" using modified anti-C5 antibodies without tethering to specific diseases or patient populations. The court emphasized that such untethered treatment language increases the written description burden beyond what a sparse specification can support.
These rulings clarify that method-of-treatment claims may withstand Section 112 invalidity challenges if the antibody genus is well known in the art and its class effect in the claimed treatment is undisputed, building on precedents like Amgen.
For in-house legal teams and law firms managing pharmaceutical IP portfolios, these decisions underscore the importance of precise claim drafting and solid evidentiary support for knowledge in the art. Broad, generalized treatment claims without specificity risk invalidation, whereas well-defined claims aligned with established genus knowledge have better prospects of surviving challenges.
By the numbers:
- April 16, 2026 — Teva v. Eli Lilly Federal Circuit decision date
- March 13, 2025 — In re Xencor Federal Circuit decision date
- Anti-CGRP antagonist antibodies — compounds involved in Teva's patent claims
- Fc substitutions M428L/N434S — modifications in Xencor's patented antibody claims
Yes, but: While Teva v. Eli Lilly supports broader genus claims with adequate support, In re Xencor illustrates that claims lacking disease or patient specificity remain vulnerable to written-description rejection.
What's next: Legal teams should monitor how these standards are applied in upcoming pharmaceutical patent litigations and adjust claim strategies accordingly.