Double Patenting

Statutory double patenting

Obviousness-type double patenting (ODP)

Term tie

The patent with the TD expires no later than the reference (first) patent. Any term extension (including patent term adjustment, PTA) cannot push the term past the reference patent's expiration. Effectively, the two patents expire together.

Common ownership

The applicant must agree that the disclaimed patent will only be enforced while under common ownership with the reference patent. If the two patents are separated (sold to different owners), the disclaimed patent's claims become unenforceable — not invalid, but unenforceable.

Filing the TD

File a terminal disclaimer form (PTO/SB/25 or PTO/SB/26) identifying the reference patent or application. Pay the fee. Sign by applicant(s) or attorney. The TD is recorded in the prosecution history and cited in the issued patent.

When NOT to file

If you believe the ODP rejection is improper — the claims are not actually obvious over the reference claims — traverse the rejection on the merits first. Filing a TD unnecessarily shortens the patent term and adds the common ownership constraint for no benefit.

What is obviousness-type double patenting (ODP) and how is it different from statutory double patenting?

Statutory double patenting arises when claims in a second patent are legally identical to claims in the applicant's first patent — the exact same invention claimed twice. It is based on 35 U.S.C. § 101 ('A person shall be entitled to a patent') and cannot be cured by a terminal disclaimer. Obviousness-type double patenting (ODP) is a judicially created doctrine — not in the statute — that prevents an applicant from claiming obvious variants of their own already-patented invention in a second patent to extend exclusivity. Under ODP, the claims are not identical but are obvious over the reference claims. ODP is the more common form in modern prosecution. It can be cured by filing a terminal disclaimer. The policy: the patent system grants a single 20-year monopoly per invention. An applicant who patents compound X, then files a continuation to patent obvious variant Y, would effectively get two 20-year monopolies that together extend the exclusivity period. ODP prevents this. After Allergan, Inc. v. Sandoz, Inc. (Fed. Cir. 2015) and subsequent cases, ODP analysis uses the same two-way test used for prior art obviousness: (1) are the claims of the second application obvious over the claims of the reference application (one-way); and (2) for cases where the applications were filed close in time and the earlier-filed application is used as reference, courts may require the two-way test — also checking whether the reference claims are obvious over the challenged claims.

What is a terminal disclaimer and when should you file one?

A terminal disclaimer (TD) is a filing with the USPTO in which the applicant: (1) dedicates to the public any portion of the challenged patent's term that extends beyond the expiration date of the reference patent; and (2) agrees to maintain common ownership of both the challenged patent and the reference patent (or application) for the term of the challenged patent. Effect: the second patent expires on the same date as the first patent — there is no term extension; the two patents must remain under common ownership throughout their term (if they are separated, the second patent's claims are unenforceable). When to file a TD: when the USPTO issues an ODP rejection in prosecution — usually the standard response is to file a TD to cure the rejection and continue prosecution. Filing a TD is a business decision that should be evaluated strategically: it limits the second patent's term, but allows the additional claims to issue; the requirement of common ownership throughout the term means a future sale or license of one patent must include both. Do NOT file a TD unnecessarily: if you believe the ODP rejection is improper, you can traverse the rejection; but if the rejection is valid (the claims are likely obvious over the reference), a TD is typically the efficient cure.

Can obviousness-type double patenting be used as an invalidity defense in litigation?

Yes. Obviousness-type double patenting (ODP) can be raised as a defense in patent litigation by an accused infringer. A patent that was not properly restricted by a terminal disclaimer may be invalid if the claims are obvious over the claims of another patent owned by the same entity. Key points: (1) ODP invalidity is decided by the court (not a jury) because it is an equitable doctrine; (2) the accused infringer must identify the reference patent or application that the challenged claims are obvious over; (3) the standard for ODP invalidity in litigation uses the patent-claim-based obviousness test — not prior art obviousness, but obviousness over the applicant's own earlier claims; (4) if ODP invalidity is found, the claims are invalid — not merely unenforceable. Common litigation scenario: generic drug company challenging a pharmaceutical method-of-treatment patent as obvious over the brand company's earlier compound patent, where both are owned by the same brand company. If the compound patent was the reference patent and has already expired, and the method patent extended the effective exclusivity, ODP can be a powerful tool to invalidate the method patent and enable generic entry.

Does a terminal disclaimer affect the patent term?

Yes — a terminal disclaimer directly limits the term of the patent by tying its expiration date to another patent's expiration date. By definition, the patent with the TD cannot expire later than the reference patent. This can significantly reduce the effective life of the disclaimed patent. Calculation example: If Patent A (reference) expires on January 1, 2030, and Patent B (challenged) would otherwise expire on July 1, 2033 based on its own filing date and any patent term adjustments (PTA), a terminal disclaimer requires Patent B to expire no later than January 1, 2030 — cutting 3.5 years off its term. Additionally, the terminal disclaimer requirement of common ownership means: if the company sells Patent A but retains Patent B, Patent B's claims become unenforceable (because common ownership is broken). This has practical implications for licensing deals, divestitures, and bankruptcy proceedings. When evaluating whether to file a terminal disclaimer: consider the term of the reference patent; calculate the expected remaining term of the challenged patent without the TD; determine whether the value of the additional claims is worth the term limitation; evaluate common ownership implications for future business transactions. Note: patent term extension under 35 U.S.C. § 156 (Hatch-Waxman) does not extend past the terminal disclaimer date — the TD caps the term even if a PTE would otherwise extend it.

How does double patenting apply to continuation patents?

Continuation patents are the most common context in which obviousness-type double patenting arises. A continuation is a second application that claims the benefit of a parent's filing date and must have the same specification (no new matter). The claims in a continuation can be broader or narrower than the parent's claims, can cover different aspects of the invention disclosed in the specification, or can be directed to different embodiments. ODP in continuations: if the continuation's claims are obvious over the parent's claims (or any issued claims in the same family), the continuation is subject to ODP rejection — even though the applications are from the same inventive entity, the patent system won't allow the second patent's claims to extend the monopoly by covering obvious variants. Common scenario: a company files a patent application (parent) that claims method of making compound X. It then files a continuation claiming the method of using compound X (the use was disclosed but not claimed in the parent). The continuation's method-of-use claims may be obvious over the parent's method-of-making claims — ODP rejection. Fix: file a terminal disclaimer tying the continuation's term to the parent's term, or amend the continuation's claims to sufficiently differentiate them from the parent. Strategic consideration: in building a patent portfolio around a core invention, applicants should plan for ODP by drafting continuation claims that are either clearly non-obvious over parent claims OR by planning to file terminal disclaimers, understanding the term implications.