Ex Parte Reexam Post-Grant Review (PGR) Inter Partes Review (IPR)
Who can initiate? Patent Owner or Third Party Third Party OnlyThird Party Only
Deadline for Filing After grant, up to 6 years past expiration Within 9 months after grant 9 months or more after grant
Length of Time 24-36 months 12-18 months 12-18 months
Basis for Filing Printed prior art All grounds Printed prior art
Overseeing Branch Different USPTO Examiner PTAB JudgesPTAB Judges
Discovery/Evidence Declaration Declaration & Depositions Declaration & Depositions
Appeal PTAB then Federal Circuit
(Only Patent Owner)
Federal Circuit
(Both Parties)
Federal Circuit
(Both Parties)
Extent of Estoppel
after Final Decision
None Both Parties Both Parties