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Double Patenting

Double patenting describes a situation in which an inventor improperly attempts to obtain more than one patent claiming either the same invention, or very similar inventions. Double-patenting doctrine was developed by the courts through a line of cases dating to 19th century Supreme Court decisions.

Modern cases distinguish between two types of impermissible double patenting. The first type, sometimes called statutory double patenting, derives from Section 101 of the Patent Act of 1952, which provides that “whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter . . . may obtain a patent therefor” (emphasis added). Inventors thus cannot obtain a second patent claiming the same invention that they have already patented.

Because Section 101 only prohibits a second patent claiming an invention identical to an earlier patent, an applicant could “evade this statutory requirement by drafting claims that vary slightly from the earlier patent.” To address that concern, courts developed a second double-patenting prohibition, called nonstatutory double patenting or obviousness-type double patenting (OTDP). OTDP prohibits patent holders from acquiring a second patent on an invention that is an obvious variation on one of their earlier patents (i.e., different in only trivial or easily discovered ways). Under this doctrine, when a later patent’s claims are obvious in light of an earlier patent filed by the same inventor, the second patent is said to be not “patentably distinct” and invalid for that reason.

The prohibition on statutory double patenting is absolute—if two patents claim the same invention, the second patent is invalid. A rejection based on OTDP, however, can be overcome during patent prosecution through a terminal disclaimer, as explained below.

Procedurally, a double patenting issue may arise in several ways. First, double patenting may result from two unrelated but commonly owned patents or patent applications that claim similar subject matter. Double patenting may also arise in the context of related patent applications, which USPTO calls “continuing applications.” A continuing application shares at least one inventor and some or all of the technical disclosure contained in an earlier pending patent application. The Patent Act and USPTO provide for several types of continuing applications, including continuations, continuations-in-part, and divisional applications. Under some circumstances, these later patent applications may “claim priority” to the earlier application—that is, the later application uses the earlier application’s filing date when determining the claimed invention’s novelty and nonobviousness. Colloquially, the earlier patent to which a continuing application claims priority is sometimes called the “parent” patent, and the continuing applications the “child” patents. Depending on the circumstances, child patents may have terminal disclaimers so that they expire at the same time as the parent patent.

Terminal Disclaimers

Statutory and Regulatory Basis

Patent law first provided for terminal disclaimers via statute in 1952. Section 253 of the Patent Act provides that “any patentee or applicant may disclaim or dedicate to the public the entire term, or any terminal part of the term, of the patent granted or to be granted” (emphasis added). An influential legislative history of the Patent Act of 1952 explained that proponents of the terminal disclaimer provision thought it might be used “in combatting a defense of double patenting, to permit the patentee to cut back the term of a later issued patent so as to expire at the same time as the earlier issued patent and thus eliminate any charge of extension of monopoly.”

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37 C.F.R. § 1.321 sets forth the current procedures for making terminal disclaimers. Subsection (c) permits the use of terminal disclaimers to “obviate” (i.e., avoid) OTDP rejections during patent prosecution. Thus, if a USPTO patent examiner initially rejects the proposed claims in a patent application based on OTDP, the applicant has a choice. He can either (1) contest the OTDP rejection on its merits (e.g., by arguing that the second patent is patentably distinct, or by proposing different claims), or (2) avoid the OTDP issue entirely via a terminal disclaimer. The second path sidesteps a fight with USPTO on the substance of whether the second patent’s claims are indeed obvious in light of the first patent, at the cost of a shortened term for the second patent.

To make a terminal disclaimer, the patent applicant must state the portion of the patent term disclaimed, pay a fee, and provide that any resulting patent will be enforceable only while it is commonly owned with the earlier patent on which the OTDP rejection was based. The common ownership condition is designed to ensure that patents tied together by a terminal disclaimer remain owned by the same entity. If ownership of one of the patents is transferred without the other, then the terminally disclaimed patent becomes unenforceable under USPTO’s rules.

Historical Development

The use of terminal disclaimers to overcome challenges to patent validity based on OTDP derives from case law following the enactment of the Patent Act of 1952. In a series of cases in the 1960s, the U.S. Court of Customs and Patent Appeals (CCPA) held that a terminal disclaimer could be used to obviate an OTDP problem. In these decisions, CCPA reasoned that OTDP was “grounded in public policy and primarily intended to prevent prolongation of monopoly”—that is, to prevent the patent holder from extending his patent term through a later-issued patent on essentially the same invention. (At the time, a later-issued patent would always expire after an earlier-issued patent.) The CCPA reasoned that a terminal disclaimer of any “excess” patent term in the later-issued patent—so that both patents expire at the same time—“foreclosed the possibility of such an extension” of the patent monopoly. The CCPA thus concluded that a “terminal disclaimer [that] causes two patents to expire together” was “tantamount for all practical purposes to having all the claims in one patent.” The effect of the disclaimer, then, is to treat the claims in the second patent application as if they were in the first application for OTDP purposes, so long as the applicant agrees that both patents will expire at the same time.

The U.S. Court of Appeals for the Federal Circuit, shortly after its creation by Congress in 1982, adopted the decisions of the CCPA as binding precedent for the new court. Thus, CCPA holdings on OTDP from the 1960s are still cited in contemporary cases, which continue to adhere to the rule that a terminal disclaimer obviates an OTDP rejection.

Recent Executive and Administrative Developments

On July 9, 2021, President Biden issued an executive order titled “Promoting Competition in the American Economy.” Among other things, the order directed the Commissioner of the U.S. Food and Drug Administration (FDA) to communicate with USPTO about whether the patent system may “unjustifiably delay generic drug and biosimilar competition beyond that reasonably contemplated by applicable law.” (Like any other invention, new drugs and biologics may be protected by patents, which may deter or delay market entry of generic and biosimilar versions of those products.)

In 2021 and 2022, FDA and USPTO exchanged a series of letters on this topic and announced several initiatives “to ensure that the U.S. patent system properly and adequately protects innovation and is not used to unjustifiably delay . . . more affordable versions of pharmaceuticals into the hands of Americans who need them.” Among the concerns raised by FDA in its letters was the use of continuing patents to “create ‘patent thickets’ by obtaining multiple patents on different aspects of the same product.” USPTO

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responded that it may “[r]evisit obviousness-type double patenting practice,” noting that “[a]lthough a terminal disclaimer ensures that the later patent will remain commonly owned with and have the same patent term as the earlier patent, multiple patents directed to obvious variants of an invention could potentially deter competition if the number of patents is prohibitively expensive to challenge.”

On October 24, 2022, USPTO issued a formal Request for Comments (RFC) on the initiatives outlined in its letter to FDA, including its proposal to revisit its regulations on OTDP and terminal disclaimers. As relevant here, USPTO sought comment on whether to “limit or change” its OTDP practice. For example, the RFC proposed “requiring applicants to stipulate that the claims are not patentably distinct from the previously considered claims as a condition of filing a terminal disclaimer,” or treating the terminal disclaimer as an admission of obviousness so that a family of patents tied by terminal disclaimers would “stand and fall together.” USPTO received more than 200 comments from stakeholders and the public.

USPTO’s May 2024 notice of proposed rulemaking (NPRM) would amend terminal disclaimer practice in a different way than envisioned in the RFC, but to a similar end. The NPRM noted that some commenters argued that requiring an applicant to stipulate that a terminally disclaimed patent’s claims are not patentably distinct conflicted with case law. For example, the Federal Circuit held in SimpleAir, Inc. v. Google LLC (Fed. Cir. 2018) that a terminal disclaimer does not operate as an admission regarding the obviousness of the resulting patent’s claims. Arguably, then, the RFC’s proposals were outside of USPTO’s regulatory authority. Instead of a stipulation about patent validity, USPTO’s proposed rule instead imposes a “condition upon enforcement” of the disclaimed patent when a terminal disclaimer is used. USPTO cites In re Van Ornum (CCPA 1982), which concerned the condition that a terminally disclaimed patent must be commonly owned to be enforced, in support of its regulatory authority.

The NPRM’s proposed rule would require that an applicant using a terminal disclaimer to overcome OTDP must agree that the enforceability of any disclaimed patent depends on the validity of any patent tied to the disclaimed patent through a terminal disclaimer. In particular, if any claim of the referenced patent is held unpatentable or invalid on certain grounds by a final decision of a federal court or by the USPTO (for example, through an inter partes review), then the disclaimed patent cannot be enforced under the proposed rule. This rule would still apply when a disclaimed patent is tied indirectly to another patent, such as when a disclaimed patent is connected through “multiple intermediate patents/applications.” For example, the disclaimed patent Z would be unenforceable if tied by a terminal disclaimer to patent Y, which is in turn tied to patent X, should a claim of patent X be invalidated. The proposed enforceability rule would be “unidirectional,” however: the condition applies only to the disclaimed patent (and not to a referenced patent lacking any terminal disclaimer). Thus, in the preceding example, a court’s determination that patent Z is invalid would not affect the referenced patents Y or X.

Considerations for Congress

USPTO’s NPRM posits that its proposed rule on terminal disclaimers would “promote competition by lowering the cost of challenging groups of patents tied by terminal disclaimers, resulting in reduced barriers to market entry and lower costs for consumers.” Proponents of USPTO’s proposed rule on terminal disclaimers argue that it would help eliminate patent “thickets” and improve patent quality. On this view, the proposed rule would likely reduce the use of terminal disclaimers, leading to fewer patents with redundant claims and more streamlined patent validity disputes. A 2023 letter from two Members of Congress supported this notion, urging USPTO to adopt a rule where patents tied together by terminal disclaimers “stand or fall together.”

Opponents of the proposed rule urge USPTO not to adopt it for several reasons. As noted above, some doubt that the USPTO has the regulatory authority to promulgate such a “substantive” rule imposing conditions on patent enforceability. Other commentators note that the rule departs from the usual patent law principle that each patent claim’s validity is assessed independently, as it would render unenforceable