Two Patents, One Invention: USPTO’s Double-Patenting Trap for Biotech

Executive Summary
On August 6, 2026, a USPTO Appeals Review Panel held that an obviousness-type double patenting (OTDP) rejection can stand even when the applicant gains no improper extension of patent term. The Panel relied on the anti-harassment rationale for OTDP rejections: the concern that separately owned patents covering obvious variants could each be asserted against the same defendant. This case, which drew eleven amicus briefs, entrenches a significant trap for biotech companies. An OTDP reference need only share one inventor, but the standard cure, a terminal disclaimer, requires common ownership. A former founder’s or collaborator’s later patent can therefore block a company’s own foundational application, leaving no cure available. Notably, the Panel applied this rule only because it considered itself bound by Federal Circuit precedent, stated it would abolish the practice if it could, and expressly invited the Federal Circuit to overturn it in a pending appeal.

Key Terms

• Obviousness-type double patenting (OTDP). A court-created rule that stops an applicant from obtaining two patents on what is essentially the same invention, including obvious variations of it.
• OTDP reference. The patent or application an examiner cites against the claims under examination. A reference need only share one inventor with the application; common ownership is not required.
• Actual filing date. The day a particular application was itself filed at the USPTO.
• Patent term filing date. The day the earliest non-provisional application in the same family was filed. This is the date used to calculate expiration. In a family built through continuation filings, an application can have a recent actual filing date but a much older patent term filing date.
• Terminal disclaimer. A legal document that gives up any patent term in the second-filed case extending beyond the first-filed case, so both expire on the same day. It is the usual way to overcome an OTDP rejection, but it can only be filed where the two cases are commonly owned.
• Appeals Review Panel (ARP). A panel the USPTO Director can convene to review a Patent Trial and Appeal Board decision, including on the Director’s own initiative.

Key Takeaways for Life Sciences Companies

• The ARP’s decision confirms that a commonly owned patent claiming an obvious variant of a pending application’s claims can serve as an OTDP reference against that pending application, even if the pending application would expire before the reference patent.
• Critically, the reference patent need not be commonly owned. Because an OTDP reference need only share an inventor with the application under examination, the ARP acknowledged that the standalone anti-harassment rationale can set a “trap” for applicants: a co-inventor’s later-filed patent, owned by a different company, can serve as an OTDP reference against the original, foundational patent. A terminal disclaimer cannot cure this, because a disclaimer can be filed only when the OTDP reference and the application at issue are commonly owned.
• This is a live risk for early-stage companies. Founders, academic collaborators, and consultants who later move to another institution or spin-out frequently file improvement patents naming the same inventors, and those filings can become uncurable OTDP references against the company’s foundational applications.
• The rule may not last. The ARP applied the standalone anti-harassment rationale only because it considered itself bound by Federal Circuit precedent, said it would abolish the practice if it could, and invited the Federal Circuit to overturn it in In re: Ablynx N.V0F . Companies weighing costly portfolio remediation should factor in that the agency enforcing this rule expects it may be revisited in the near term.

Why Should Life Sciences Companies Care?
This decision carries immediate consequences for life sciences companies, which routinely build patent families around a single drug or platform technology. Filings on new species, formulations, methods of use, and manufacturing improvements follow the original applications and often name overlapping inventors.

• Companies should evaluate their patent application filing strategy with respect to claim scope and timing — specifically, whether to file an initial application containing only broad genus1F claims or to include both genus and species2F claims in a single application. Splitting genus and species claims across separate, later filings creates families of obvious variants with differing filing dates, precisely the pattern that generates OTDP references; capturing both in one application reduces the number of later filings that can be cited against each other.
• Companies should review their patent portfolios to identify pending continuation applications and assess whether proactively filing a terminal disclaimer would be advisable. Before filing any terminal disclaimer, companies should also determine whether doing so would require surrendering any patent term adjustment to which the patent is otherwise entitled, and weigh that potential loss against the benefits of avoiding an OTDP rejection during examination and a later challenge to the patent’s enforceability.
• While terminal disclaimers remain the primary tool for overcoming OTDP rejections, companies would need to conduct proper due diligence before entering into any joint ventures and/or license agreements in which patent families are licensed to multiple parties.
• Companies should monitor notices of allowance from the USPTO in related cases, including cases owned by former collaborators. An allowance in a later-filed case that shares an inventor but not ownership can become an OTDP reference against the company’s own earlier-filed, still-pending application, and no terminal disclaimer will be available to overcome it. Where that risk arises, the pending claims may need to be amended or restructured before the reference issues.

What Actually Is Obviousness-Type Double Patenting (OTDP)?
OTDP is a judicially created doctrine that prevents an applicant from obtaining two patents on essentially the same invention (i.e., obvious variants of each other). The rule exists to ensure that the public can use the invention once the statutorily granted monopoly expires. If an applicant could keep filing new patents on minor tweaks to the same idea, the applicant could extend that exclusivity well beyond the term the law allows.

Patent examiners assess OTDP by comparing the claims of a pending patent application with those of issued patents or pending applications that share at least one inventor with, or are commonly owned with, the application under examination. If the claims of a pending application cover an obvious variation of an already patented invention, the examiner rejects the new claims for OTDP. An applicant can usually overcome the OTDP rejection by filing a terminal disclaimer, a document that waives any patent term in the second-filed case that extends beyond the term of the first-filed case. As a result, the second-filed patent will expire on the same date as the first-filed patent. One important requirement for filing a terminal disclaimer (and later enforcing the patent) is that both patents must be jointly owned. Note the asymmetry, which drives much of the decision discussed below: a patent can be used as an OTDP reference against an application if it merely shares an inventor, but a terminal disclaimer can be filed only if the two cases are also commonly owned.

Why Did the Board Reverse the Examiner?
The Board reversed the examiner’s OTDP rejection in Ex parte Baurin, relying on Allergan USA, Inc. v. MSN Laboratories Private Ltd.3F
In Allergan, the Federal Circuit held that “a first-filed, first-issued, later-expiring claim cannot be invalidated by a later-filed, later-issued, earlier-expiring reference claim having a common priority date.” In other words, the case addressed what happens when an earlier-filed, earlier-granted patent has a longer term than a later-filed sibling patent. The court held that, in this situation, the earlier-filed patent is not subject to an OTDP rejection merely because a later, related patent expires sooner. The Federal Circuit’s holding applies when all of the following conditions are met: (1) the claim for which invalidation is sought must be the first-filed and first-issued claim; (2) that claim must be later-expiring than the reference claim; and (3) the challenged claim and the reference claim must share a common priority date.

The Appeals Review Panel’s (ARP’s) Decision
Allergan Does Not Apply to Baurin
The ARP first addressed whether the Federal Circuit’s 2024 Allergan decision applied to the facts at hand. The ARP determined that none of the three prongs of Allergan’s holding were satisfied in the ’529 Application. The “first-filed” prong was not met because the ’529 Application did not have the earliest actual filing date in its family. The second prong was not met because the ’529 Application was still pending. The third prong was not met because the ’529 Application and the OTDP reference patent (U.S. Patent No. 10,882,922) had different patent term filing dates (March 28, 2012 vs. April 13, 2017). The ARP interpreted “first-filed” in Allergan as referring to actual filing dates, not patent term filing dates. Having held that Allergan did not apply, the ARP then considered whether the rejection of the ’529 Application was at odds with the rationale behind OTDP rejections.

The Anti-Harassment Rationale Independently Supports OTDP Rejections
The ARP next addressed the Board’s holding that the anti-harassment rationale cannot independently support an OTDP rejection — in other words, that it cannot serve as a standalone basis for rejecting claims when no improper term extension is present. The primary purpose of OTDP rejections is to prevent unjust patent term extension by a patent holder through patenting an obvious variant. The Federal Circuit has recognized a second reason for OTDP beyond preventing unjust time-wise extension – the prevention of harassment of a third party by multiple lawsuits. If a company splits ownership of two patents, each covering obvious variants of the same invention, each owner could separately sue the same third party for infringement of what is essentially the same invention. The anti-harassment rationale prevents this outcome by treating the second application as unpatentable, or, if ownership splits after issuance, treating the second patent as unenforceable.

The ARP reversed the Board’s conclusion that the anti-harassment rationale is “immaterial” and cannot independently support an OTDP rejection. The ARP traced the anti-harassment rationale through Federal Circuit precedent, focusing primarily on In re Hubbell4F and In re Fallaux5F . In both cases, the court affirmed OTDP rejections based on the anti-harassment rationale even when no term-extension concern was present. The ARP also cited In re Cellect6F , LLC, where the court identified the risk of separate ownership as a reason to uphold OTDP rejections. The ARP rejected the Board’s attempt to dismiss the anti-harassment discussions in Fallaux and Hubbell as mere dicta7F , reasoning that treating those discussions as dicta would mean the court affirmed the OTDP rejections without any underlying rationale.

The Director’s Invitation to the Federal Circuit
Despite sustaining the examiner’s OTDP rejections on anti-harassment grounds, the ARP made clear that it views the current state of the law as problematic. The ARP stated that, were it not bound by Federal Circuit precedent, it would clarify that the risk of separate ownership and hypothetical harassment generally should not serve as a standalone basis for OTDP rejections during examination. The ARP reasoned that, absent actual evidence that an applicant has split ownership to facilitate harassment, the Office is merely speculating about contingencies that may never arise. The ARP expressly invited the Federal Circuit to provide clarification, stating: “If, contrary to our conclusion here, the Federal Circuit’s precedents should not be read as permitting OTDP rejections based on the anti-harassment rationale where no term-extension concern is apparent, the Office would welcome that clarification from the court.” The ARP flagged In re: Ablynx N.V. as the pending case in which the Federal Circuit may address this question.

The ARP also proposed potential limitations on the anti-harassment rationale if it remains in place. One option would require actual evidence of prior ownership splitting and resulting harassment before the rationale could be used on its own. Another option would impose a “two-way test,” requiring the examiner to show that the challenged claims and the reference claims are each obvious over the other before a standalone anti-harassment OTDP rejection could be made. This two-way test would give applicants a more realistic path to overcome the rejection.

Guidance to USPTO Personnel on Allergan
The ARP concluded its decision by providing guidance to the examiners. The ARP directed USPTO personnel to continue following pre-Allergan OTDP practice under MPEP Section 804 unless two conditions are met: (1) the application and the OTDP reference are in the same family and share the same patent term filing date, and (2) the claims under examination are first-filed, first-issued, and later-expiring. The ARP noted that this situation will rarely arise during original examination because an examiner will rarely be able to confirm that the claims under examination will be first-filed, first-issued, and later-expiring.

A Proposed Future Framework for OTDP
The ARP decision also proposed a framework for OTDP examination. It stated that examiners should compare patent term filing dates when the application under examination and the OTDP reference patent or application belong to different patent families. For cases where the application under examination and the reference patent/application belong to the same family, the examiners are instructed to compare actual filing dates.

As noted above, the Federal Circuit is poised to address these questions in In re: Ablynx N.V., which may bring definitive clarification to the circumstances under which an OTDP rejection may rest solely on the anti-harassment rationale.

Appendix: Procedural History
The ’529 Application was rejected by the Examiner for obviousness-type double patenting over five issued patents and one pending application (six rejections in total)8F . The Examiner relied on MPEP § 804, which covers the double patenting doctrine, including OTDP.
Sanofi, the applicant, appealed to the Patent Trial and Appeal Board, arguing that none of the cited patents qualified as OTDP references: each had a later patent-term filing date than the ’529 Application and would expire after it, so no improper extension of term was possible. The Board agreed and reversed all six rejections, finding that the cited patents could not serve as proper OTDP references because the ’529 Application’s claims were first-filed and earlier-expiring. The Board also noted, in passing, that the risk of separate ownership is “immaterial” when no proper OTDP reference exists.
The Examiner sought rehearing, arguing that the Board had misread Allergan, departed from USPTO guidance on OTDP, and lacked support in case law for treating the risk of separate ownership as immaterial. The Board reaffirmed its reversal. The Director then convened the ARP sua sponte — on the Director’s own initiative, without a request from either party — to review the rejection.

Full Article with footnotes can be found here.