Lose the priority date, gain a post-grant review

How to read the ledger below. Each numbered point carries the kind of evidence behind it. ESTABLISHED is stated in the authority's own text, with a locator. IMPLEMENTED is the rule as the authority actually applied it. OBSERVED is carried by a source outside this one. ASSUMED is the drafter's inference, flagged as such and not the authority speaking. Quotations are checked against a cached copy of the primary source by script.

In one paragraph

The Federal Circuit affirmed the Patent Trial and Appeal Board in Purdue Pharma v. Collegium on 21 November 2023 on 2 separate questions, and the one that matters for continuation practice is that the application Purdue claimed priority to did not describe the claimed aversive agent, so the effective filing date fell after 16 March 2013 and the patent was eligible for post-grant review it would otherwise have escaped. The court separately held that the Board keeps authority to issue a final written decision after its statutory deadline has passed, which is the holding the conclusion states.

Reader summary

Purdue's patent claimed priority to a 2001 application. Applications filed before March 16, 2013 are not subject to post-grant review, so if that priority claim held, the patent was outside the proceeding entirely. Purdue made exactly that argument.

It failed, and it failed on ordinary written description. The specification of the priority application did not adequately describe the claimed aversive agent, a class of polyglycolyzed glycerides, so the effective filing date fell after March 16, 2013 and the patent was PGR-eligible. The Federal Circuit affirmed that finding on substantial evidence, applying the blaze-marks framing: a specification must guide a reader through the forest of disclosed possibilities toward the claimed compound.

The opinion's headline holding is a different matter. The Board issued its final written decision after the statutory one-year deadline had passed, and the court held that missing that deadline does not strip the Board of authority to decide.

For this corpus, the first holding is the one that matters, and it makes a point the rest of Tier C does not: an effective filing date is not only about prior art. It is also a jurisdictional fact that determines which post-grant proceedings can reach the patent at all. snipr-v-rockefeller makes the same point from the other direction, about interferences.

Why this matters when you are drafting

A priority claim can be doing jurisdictional work you have not priced. Claims 3, 4 and 7. Where a family reaches back before March 16, 2013, the priority claim is what keeps the patent out of post-grant review. Written-description support for the claimed subject matter is therefore load-bearing twice over, and a defect that would merely cost an early date in another family can here open a proceeding.

The failure mode is the familiar one. Claim 6 is blaze marks: the priority document disclosed possibilities, and the claims picked one out. That is the same shape as the written description records in Tier B, and it is the most common way a continuation's reach back fails.

Do not cite this case without saying which holding. Claim 8. The CONCLUSION supports a proposition about Board deadlines and nothing about priority. A cite to Purdue v. Collegium for a priority proposition will not survive a reader who opens it at the last page.

Pair it with SNIPR. Both show the same 2013 boundary deciding which proceedings reach a patent, one for interferences and one for post-grant review. Together they make the point that an effective filing date is a jurisdictional fact and not only a prior-art fact.

What the authority establishes

1. [ESTABLISHED, the disposition and the headline holding] "We affirm that the Board has authority to issue a Final Written Decision after the statutory deadline has passed." (P. 15.)

1. [ESTABLISHED, the headline holding restated] "the Board's failure to comply with the statutory deadline does not deprive it of authority thereafter to issue a final written decision". (P. 13.)

1. [ESTABLISHED, the eligibility argument Purdue made, and the reason this record is in Tier C] "In the PGR, Purdue argued that the '961 patent was not subject to PGR as it claimed priority to an August 6, 2001, application" and pre-2013 applications are not subject to post-grant review. (P. 3.)

1. [ESTABLISHED, why the argument failed] The priority application did not contain sufficient written-description support for the claimed invention, "and the effective filing date was therefore after March 16, 2013". (P. 4.) The patent was consequently PGR-eligible.

1. [ESTABLISHED, the affirmance on that point] On whether the specification adequately disclosed the claimed aversive agent, "We conclude that substantial evidence supports the Board's finding". (P. 14.)

1. [ESTABLISHED, the written-description standard applied] The court required that a specification "provide sufficient 'blaze marks' to guide a reader through the forest of disclosed possibilities toward the claimed compound". (P. 13.)

1. [IMPLEMENTED, the chain that makes this a Tier C case] The court's own sequence is: the claims require an aversive agent; the priority specification does not describe the claimed class as that agent; so the priority claim fails; so the effective filing date is post-2013; so the patent is within post-grant review. A written-description defect became a jurisdictional exposure, not merely a prior-art one.

1. [ASSUMED, drafter's inference, flagged as such] The two holdings are independent, and a reader who takes only the CONCLUSION will carry away a PTAB-procedure rule and miss the priority holding entirely. The opinion does not flag this; it follows from the CONCLUSION stating one holding while the analysis decides two.

Quotations, verified against the source

All from the Federal Circuit's opinion. Page locators computed from the docket stamp.

• "In the PGR, Purdue argued that the '961 patent was not subject to PGR as it claimed priority to an August 6, 2001, application" (P. 3.)
• "the effective filing date was therefore after March 16, 2013" (P. 4.)
• "provide sufficient 'blaze marks' to guide a reader through the forest of disclosed possibilities toward the claimed compound" (P. 13.)
• "the Board's failure to comply with the statutory deadline does not deprive it of authority thereafter to issue a final written decision" (P. 13.)
• "We conclude that substantial evidence supports the Board's finding" (P. 14.)
• "We affirm that the Board has authority to issue a Final Written Decision after the statutory deadline has passed" (P. 15.)

Tensions and open questions

The priority holding is an affirmance on substantial evidence, not a legal rule. Claim 5. It tells you the Board's finding was supportable on this record; it does not announce a standard beyond the blaze-marks framing the court was already applying.

The deadline holding is genuinely out of this corpus's scope and is included only for accuracy. Recording it prevents the record from misdescribing the case, but nothing in Tier C should be built on it.

How the eligibility determination interacts with a later successful priority argument is unaddressed. If a patentee were to establish priority in a different forum, whether that unsettles a completed post-grant review is not something this opinion reaches.

What this record does and does not cover

The written-description analysis and the PGR-eligibility posture were read in full, because they are the reason this record exists.

What was NOT read closely, and is therefore outside what this record can support: the statutory-deadline analysis beyond its holding and the outline of its reasoning, and the bankruptcy-stay discussion. This record cannot support any proposition about why the deadline holding came out as it did, or about how the Supreme Court authorities it relies on apply elsewhere. The Board decision, the patent, and the priority application are known here only through the court's characterization.

Currency

This record was verified against its primary source on 2026-08-15. That is a fidelity check: the quotations, locators and attribution are accurate to that source. Whether the authority has since been narrowed, distinguished, abrogated or reversed has not been checked here. Confirm it still stands before relying on it.