USA Law and Practice Contributed by: Jim Hurst, Jeanna Wacker, Sam Kwon and Ashley Ross, Kirkland & Ellis
Certain districts have local rules that provide for exchange of contentions in which parties explain their theories of infringement and invalidity. Par - ticular procedures for discovery tools (such as restrictions on the type or scope of discovery) may further vary depending on the district or judge. 1.15 Defences and Exceptions to Patent Infringement There are several defences available in infringe - ment actions. Patent invalidity can be proven through multiple statutory avenues, such as: • failing to provide a sufficient written descrip - tion or failing to enable a person skilled in the art (35 USC Section 112) – the more a party claims, the broader the monopoly it demands, the more it must enable (Amgen Inc v Sanofi, 598 US 594, 613 (2023)); • anticipation by a single prior art reference (35 USC Section 102); • obviousness in light of one or more prior art references (35 USC Section 103); and • claiming patent ineligible subject matter (35 USC Section 101). Other doctrines that are judicially created, such as obviousness-type double patenting (where patent claims at issue are obvious variants of claims from a commonly owned reference pat - ent), may also be raised. For a patent that has received patent-term extension (PTE), obvious - ness-type double patenting analysis is based on the expiration date of the patent before the addi - tion of PTE (Novartis AG v Ezra Ventures LLC, 909 F.3d 1367, 1373–74 (Fed Cir 2018)). By con - trast, for a patent that has received patent-term adjustment (PTA) for delay by the PTO during prosecution, obviousness-type double patenting
analysis must be based on the expiration date of the patent after the addition of the PTA (In re: Cellect, LLC, 81 F.4th 1216, 1226 (Fed Cir 2023)). In 2024, the Federal Circuit again addressed this issue, noting that a first-filed, first-issued par - ent patent having duly received PTA cannot be invalidated by a later-filed, later-issued child pat - ent with less, if any, PTA (Allergan USA, Inc. v MSN Lab’ys Priv. Ltd., 111 F.4th 1358, 1370 (Fed Cir 2024)). Equitable doctrines may also render patents unenforceable as follows. • “Unclean hands” – a defence that can be asserted to prevent a patent owner from being granted an equitable remedy because the patent owner acted unethically concern - ing the action at issue. • Inequitable conduct – found when the pat - ent owner materially deceived the US Patent and Trademark Office (USPTO) during patent prosecution. If inequitable conduct is found, all related patent claims may be rendered unenforceable. • Equitable estoppel – proven by an accused infringer through three elements: (a) the patentee’s misleading conduct led the alleged infringer to reasonably infer that the patentee did not intend to enforce its patent against the alleged infringer; (b) alleged infringer relied on that conduct; and (c) owing to this reliance, the alleged infring - er would be materially prejudiced if the patentee is allowed to proceed with its claim (AC Aukerman Co v RL Chaides Constr Co, 960 F.2d 1020, 1028 (Fed Cir 1992)). Another defence to accusations of patent infringement is prior use by the accused infring - er, governed by 35 USC Section 273. It applies to subject matter that consists of a process,
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