The US Court of Appeals for the Federal Circuit expanded the
Markush doctrine, determining that the claim language
"comprising . . . [at least] . . . a group consisting of . .
." absent some basis or extrinsic evidence for limiting the
group, such a group could capture an alleged infringement having an
additional component present, as long as the additional component
is "functionally similar" to the component
identified in the Markush group limitation. ,Amgen
Inc. v. Amneal Pharm. LLC, Case No. 18-2414 (Fed. Cir. Jan. 7,
2020) (Lourie, J).
This case involves an abbreviated new drug application (ANDA)
litigation over Amgen's Sensipar®, a rapid dissolution
formulation of cinacalcet hydrochloride. To overcome a US Patent
and Trademark Office rejection in an office action citing prior
art, Amgen filed an amendment narrowing the cinacalcet formulation
limitation and later accepted the examiner's claim amendment
that modified the binder claim elements of the formulation
