Post-Grant Review

What is post-grant review (PGR)?

Post-grant review is a trial proceeding before the Patent Trial and Appeal Board (PTAB) of the USPTO, created by the America Invents Act (AIA), that allows a third party to challenge the validity of a recently-granted patent on essentially ANY ground of invalidity. It is one of the AIA's three main post-grant proceedings (alongside inter partes review and the now-sunset covered business method review). Defining features: (1) Broad grounds — unlike inter partes review (IPR), which is limited to anticipation (§ 102) and obviousness (§ 103) based only on patents and printed publications, PGR permits a challenge on any ground that could be raised as a defense to validity: patent eligibility (§ 101), novelty (§ 102), obviousness (§ 103), and the § 112 requirements (written description, enablement, indefiniteness), as well as double patenting — and it can rely on any evidence, including prior public use and on-sale activity. (2) Narrow timing window — a PGR petition must be filed within NINE MONTHS of the patent's grant (or reissue). After that window closes, IPR becomes the available route. (3) Limited eligibility — PGR is available only against patents subject to the AIA's first-inventor-to-file provisions, meaning patents with an effective filing date on or after March 16, 2013. (4) Institution standard — the PTAB institutes PGR if the petition shows it is 'more likely than not' that at least one challenged claim is unpatentable, or if it raises a novel or unsettled legal question important to other patents. (5) Estoppel — a petitioner who receives a final written decision is estopped from later raising, in court or the USPTO, any ground it raised or reasonably could have raised. PGR is powerful because of its breadth, but it is used far less than IPR — largely because the 9-month window requires challengers to act before they may even know a patent threatens them.

What is the difference between post-grant review and inter partes review?

Post-grant review (PGR) and inter partes review (IPR) are both AIA trial proceedings at the PTAB for challenging issued patents, but they differ in timing, grounds, and eligible patents — and the differences drive which one a challenger uses. (1) Timing: PGR must be filed within 9 months of grant; IPR can only be filed AFTER that 9-month window (or after any PGR terminates), and must be filed within 1 year of the petitioner being served with an infringement complaint. So PGR is the early-window tool; IPR is the later, ongoing tool. (2) Grounds: This is the biggest difference. PGR allows ANY invalidity ground — § 101 patent eligibility, § 102 novelty, § 103 obviousness, § 112 written description/enablement/indefiniteness, double patenting — and any supporting evidence including public use and on-sale bar. IPR is limited to §§ 102 and 103 and ONLY on the basis of patents and printed publications; you cannot challenge eligibility or enablement in an IPR, and you cannot use product prior art or sales evidence. (3) Eligible patents: PGR applies only to first-inventor-to-file (AIA) patents — effective filing date on or after March 16, 2013. IPR applies to any patent regardless of filing date, which is why IPR has been usable against the large stock of pre-AIA patents while PGR was not. (4) Institution threshold: PGR uses 'more likely than not'; IPR uses 'reasonable likelihood of prevailing' — slightly different formulations, both meaningful screens. (5) Use in practice: IPR is by far the more common proceeding — thousands of petitions — because the 9-month PGR window is short, often closing before a challenger has been sued or even identified the patent as a threat, and because filing a PGR can tip off the patentee early. PGR shines when a challenger knows early about a problematic patent and wants to attack grounds (like § 101 or § 112) that IPR cannot reach.

Why is post-grant review used so much less than IPR?

Despite offering broader grounds, PGR is filed far less often than IPR — a notable pattern given its power. The reasons: (1) The 9-month window is too early. A PGR petition must be filed within nine months of a patent's grant. But most patent disputes arise later — when a patentee asserts the patent against a product, often years after grant. By the time a company knows a patent is a threat, the PGR window has usually long closed, leaving IPR (or litigation defenses) as the only option. Companies rarely monitor every competitor patent closely enough to catch the 9-month window for patents that have not yet been asserted. (2) Tipping your hand. Filing a PGR in the first nine months publicly signals to the patentee that you view its patent as a threat — potentially inviting an infringement suit or alerting the patentee to strengthen related applications still in prosecution. Many companies prefer to stay quiet. (3) Cost with uncertain payoff. PGR (like IPR) is expensive, and committing to a full challenge before any dispute has crystallized is a hard business case — you may spend heavily to invalidate a patent that would never have been asserted against you. (4) Broad estoppel. A PGR final written decision estops the petitioner from later raising any ground it raised OR reasonably could have raised — and because PGR allows essentially all grounds, the estoppel is correspondingly broad, potentially foreclosing many defenses in later litigation. That broad estoppel makes PGR a bigger gamble than IPR (whose estoppel is confined to §§ 102/103 prior-art grounds). (5) Eligible-patent limit. PGR only applies to AIA (post-March 16, 2013) patents, so for years a large share of asserted patents simply weren't PGR-eligible. The net effect: PGR is a specialist tool used when a challenger has early knowledge of a specific problematic patent and wants grounds IPR can't reach (especially § 101 or § 112), while IPR remains the workhorse of post-grant patent challenges.

What grounds can you raise in a PGR that you cannot in an IPR?

PGR's defining advantage is the breadth of grounds, several of which are entirely unavailable in IPR: (1) Patent eligibility under § 101 — PGR can challenge claims as directed to ineligible subject matter (abstract ideas, laws of nature, natural phenomena under the Alice/Mayo framework). IPR cannot raise § 101 at all. This makes PGR a route to attack, for example, software or diagnostic patents on eligibility grounds at the PTAB rather than only in court. (2) § 112 written description and enablement — PGR can argue that the specification fails to demonstrate the inventor possessed the full claimed scope, or that it does not enable a skilled person to make and use the full claimed scope without undue experimentation (an Amgen v. Sanofi-type enablement attack on broad functional claims). IPR cannot reach § 112. (3) § 112 indefiniteness — PGR can challenge claims as indefinite under the Nautilus 'reasonable certainty' standard; IPR cannot. (4) Prior art beyond patents and printed publications — PGR can rely on prior PUBLIC USE and ON-SALE activity (the § 102(a)(1) public-use and on-sale bars), supported by evidence like product samples, testimony, and sales records. IPR is restricted to patents and printed publications as the prior-art basis, so product-based prior art is off-limits in IPR. (5) Double patenting — can be raised in PGR. In short, IPR is a focused tool for the prior-art questions of novelty and obviousness using documentary prior art; PGR is a comprehensive validity challenge encompassing eligibility, the disclosure requirements, indefiniteness, and non-documentary prior art. The trade-off for that breadth is PGR's narrow 9-month filing window, its limitation to AIA patents, and its correspondingly broad estoppel.

How does PGR fit among the other ways to challenge a patent?

PGR is one of several mechanisms for challenging an issued US patent, each suited to different circumstances: (1) Post-grant review (PGR) — broadest grounds, but only within 9 months of grant and only for AIA patents; PTAB trial; ~18 months to final decision. (2) Inter partes review (IPR) — §§ 102/103 on patents and printed publications only, available after the PGR window and within 1 year of being sued; the most-used PTAB proceeding; broad use against patents of any vintage. (3) Covered Business Method (CBM) review — a transitional PGR-like proceeding for certain financial-services business-method patents; the CBM program SUNSET in September 2020 and is no longer available for new petitions, though it was historically important for § 101 challenges to business-method patents. (4) Ex parte reexamination — any party (or the patent owner) can request the USPTO reexamine a patent based on patents and printed publications raising a substantial new question of patentability; the requester does not participate after filing (it is 'ex parte'), there is no estoppel, and it is cheaper but slower and less powerful than PTAB trials; it remains available at any time during the patent's life. (5) Supplemental examination — a patent-owner-only tool to have the USPTO consider information that could otherwise support an inequitable conduct claim, immunizing the patent if completed before litigation. (6) District court litigation — invalidity defenses and counterclaims on any ground, decided under the clear-and-convincing-evidence standard (versus the PTAB's preponderance standard), with a jury available; the venue for the broadest factual development but the slowest and most expensive. (7) ITC Section 337 — invalidity is a defense in import-related enforcement actions. Choosing among them turns on timing (how long since grant; whether you've been sued), the grounds you need (only PGR and litigation reach § 101/§ 112; IPR and reexam are prior-art only), cost, the estoppel you're willing to accept, and whether you want the speed and preponderance standard of the PTAB or the full procedural breadth of court.