Today, the Supreme Court denied three petitions for certiorari challenging the constitutionality of subjecting patents issued prior to the America Invents Act (“AIA”) to inter partes review (“IPR”). See Celgene v. Peter; Collabo v. Sony Corp.; Enzo v. Becton, Dickinson and Company. In all three underlying cases, the U.S. Court of Appeals for the Federal Circuit had rejected petitioners’ arguments that the Patent Trial and Appeal Board violated the Takings Clause of the Fifth Amendment by retroactively applying IPR to patents filed pre-AIA. In Celgene, the Federal Circuit reasoned that “[t]he validity of patents has always been subject to challenge in district court” and “IPRs do not differ significantly enough from preexisting PTO mechanisms for reevaluating the validity of issued patents to constitute a Fifth Amendment taking.” It further explained that “IPRs are the most recent legislative modification to the PTO’s longstanding reconsideration procedures,” citing to ex parte reexamination (created by Congress in 1980) and inter parte reexamination (created by Congress in 1999) procedures as other examples.