Start by Separating Statutory and Nonstatutory Double Patenting

U.S. practice recognizes two different double-patenting problems. Statutory double patenting under 35 U.S.C. §101 concerns claims to the same invention—essentially coextensive subject matter. A terminal disclaimer cannot cure that rejection; the claims must be shown to be different, amended, or canceled.

Nonstatutory double patenting, commonly called obviousness-type double patenting or OTDP, has traditionally been described as a judicially developed doctrine. In its precedential 2026 decision in Ex parte Baurin, however, the USPTO emphasized that the rule is also grounded in the history and statutory structure of the Patent Act. The doctrine addresses public-policy concerns including unjustified timewise extension and the risk of harassment through separately owned, patentably indistinct rights.

This distinction matters because “double patenting” is not a single rejection with a single cure. Before deciding strategy, read exactly which type the examiner has made and what claims are being compared.

OTDP Compares Claims, Not Entire Specifications

An OTDP analysis asks whether the examined claim is patentably distinct from the claim or claims used as the reference. The existence of common disclosure, shared inventors, or a common family relationship may explain why the issue arises, but the operative comparison is claim focused.

That means portfolio drafting can create or avoid problems. A continuation that merely shifts wording around the same inventive concept may be vulnerable even if the specifications contain many differences. By contrast, a later claim directed to a genuinely distinct invention may be defensible on the merits. The response should identify the actual difference between claim scopes and analyze whether that difference is patentable, rather than assume common ownership makes the issue inevitable.

A terminal disclaimer is a legal consequence, not a clerical form

For nonstatutory double patenting, a compliant terminal disclaimer can be a practical solution. It can also shorten enforceable term and impose common-ownership or enforcement conditions. Portfolio strategy should come before the form.

What a Terminal Disclaimer Does—and Does Not Do

MPEP §804 explains that a timely terminal disclaimer may overcome an actual or provisional nonstatutory double-patenting rejection when the relevant ownership or joint-research conditions are satisfied. It does not overcome statutory same-invention double patenting. It also does not remove a reference as prior art under §§102 or 103.

A terminal disclaimer is not, by itself, a complete reply to an Office Action. The applicant still needs a reply requesting reconsideration. And because a terminal disclaimer applies to the patent term rather than to selected claims only, its consequences should be evaluated at the patent level.

The ownership language matters as well. A terminal disclaimer filed under the common-ownership route includes an enforceability condition tied to common ownership with the identified patent or application. That may affect later assignment and licensing plans. Treating the disclaimer as harmless paperwork can create a business constraint long after prosecution ends.

Cellect Put Patent-Term Adjustment at the Center of the Debate

In In re Cellect, the Federal Circuit addressed OTDP in a family where patent-term adjustment caused some related patents to expire later. The decision intensified attention to how later expiration can interact with patentably indistinct claims and reinforced the risk of leaving OTDP unresolved until after the reference patent has expired, when a retroactive terminal disclaimer may no longer solve the problem.

The practical lesson is broader than the particular PTA facts: continuation families should be reviewed as a term-and-claim system. Filing dates, priority claims, issuance order, patent-term adjustment, patent-term extension, and the substantive relationship among claims can all matter. A portfolio spreadsheet that tracks only family relationships is not enough.

Allergan Limited Cellect in an Important Same-Family Setting

In 2024, the Federal Circuit held in Allergan USA, Inc. v. MSN Laboratories that a first-filed, first-issued, later-expiring claim could not be invalidated for OTDP by a later-filed, later-issued, earlier-expiring reference claim sharing a common priority date. That holding prevents an overreading of Cellect under which any shorter-lived family member automatically becomes an OTDP weapon against the first-filed, first-issued patent.

But Allergan did not abolish OTDP in continuation families. Its protection is fact specific. The chronology of actual filing and issuance, the patent-term filing date, and the family relationship remain essential.

Ex parte Baurin Is the 2026 Development Practitioners Cannot Ignore

On August 6, 2026, the USPTO designated Ex parte Baurin precedential. The Appeals Review Panel reinstated an OTDP rejection and confirmed that the Federal Circuit has recognized an anti-harassment rationale as a legitimate policy basis even when the particular patent would not extend the duration of the monopoly. At the same time, the panel openly questioned whether a standalone anti-harassment rationale should ultimately remain part of the doctrine.

For present USPTO practice, that means applicants should not assume that showing identical expiration dates ends an OTDP rejection. The Office continues to apply the existing MPEP framework except where a controlling case such as Allergan squarely governs the fact pattern. Baurin therefore makes chronology and claim relationships more important, not less.

Restriction and §121 Can Change the Analysis

There is also a statutory safe-harbor dimension. When the USPTO requires restriction and the applicant files a proper divisional while maintaining the required consonance between the restricted groups, 35 U.S.C. §121 can protect qualifying claims from certain double-patenting challenges. Losing consonance can jeopardize that protection.

This is one reason restriction responses should not be treated as isolated procedural events. The election, the way divisional claims are organized, and later continuation choices can affect OTDP years later. A well-maintained family map should record the original restriction groups and which claims descended from each group.

A Practical Portfolio Strategy

  • Distinguish statutory same-invention double patenting from nonstatutory OTDP.
  • Compare the actual claims and identify the asserted lack of patentable distinctness.
  • Calculate expected expiration dates, including PTA/PTE effects where relevant.
  • Check actual filing and issue chronology before relying on Allergan.
  • Consider Ex parte Baurin when arguing that equal term alone eliminates OTDP.
  • Evaluate whether a terminal disclaimer affects valuable term, assignment, licensing, or enforcement plans.
  • Preserve restriction-group consonance when a §121 divisional safe harbor may matter.
  • Resolve provisional OTDP strategically rather than simply postponing it until issuance.

Takeaway

OTDP is a portfolio doctrine disguised as a prosecution rejection. The best response cannot be chosen from the Office Action alone; it requires a view of the family, the claims, the term, and the business plan.

Sometimes a terminal disclaimer is plainly the efficient answer. Sometimes it sacrifices valuable term or creates ownership constraints that justify arguing patentable distinctness instead. In 2026, Cellect, Allergan, and Baurin make that strategic review more important than ever.

Sources & Further Reading