Double Patenting

Being Rejected Based on Your Own Work

Double patenting is a doctrine in patent law aimed at preventing the improper extension of patent rights through multiple patents covering the same invention or an obvious variations of an earlier invention by the same party. The difference between a double patenting rejection and a standard anticipation rejection or obviousness rejection is that the double patenting rejection is not a prior art rejection; it is a prohibition on extending the patent grant beyond its intended term. It is made based on the claims of the earlier patent, not "prior art". It is also worth noting that the inventive entity is the same. In other words, you are not being rejected based on someone else's prior work, you are being rejected based on your own prior patent claims. This doctrine ensures that a patent applicant cannot unjustly extend the exclusivity of their patent protection beyond the statutory patent term.

We sometimes run across the misconception that a patentee can reapply for the same invention claimed in an earlier patent. However, this misconstrues the fundamental quid pro quo of the patent system: in exchange for your valuable innovation, the US government will grant you a limited term of exclusivity to take economic advantage of your innovation. Double patenting is a violation of this fundamental bargain.

There are two primary forms of double patenting rejection: statutory double patenting and nonstatutory double patenting. Each of these versions is explained below.

Statutory Basis for Double Patenting

The statutory double patenting doctrine arises under 35 U.S.C. §101, which states that an inventor may obtain "a patent" for an invention claimed, thereby prohibiting the issuance of two or more patents for the same invention. This rejection is often referred to as a statutory double patenting rejection.

Application of Statutory Double Patenting

A statutory double patenting rejection is applied when the patent examiners determine that the claimed invention in a second patent is identical to the invention claimed in an earlier patent. Unlike nonstatutory double patenting, which relies on an obviousness analysis, statutory double patenting is strictly focused on whether the claimed subject matter in the second patent is the same as that in the earlier patent.

For a statutory double patenting rejection to be properly established, the United States Patent and Trademark Office (USPTO) must show:

1. The claimed invention in the second patent is identical to that of the earlier patent.
2. The earlier patent and the second patent share at least one common inventor or are commonly owned.
3. The same inventive concept is claimed in both patents, meaning that there are no distinct limitations between them.

Difference from a 35 U.S.C. §102 Rejection

A statutory double patenting rejection differs from an anticipation rejection in several key ways. Under 35 U.S.C. §102, a prior art reference, which may include the applicant’s own prior patent, anticipates the claimed subject matter if every element is disclosed in the reference. Rather than assessing whether a prior patent discloses every element of the claimed invention, statutory double patenting focuses on whether the earlier patent and second patent claim include the same limitations with no meaningful variation.

Additionally, ownership considerations play a crucial role in differentiating these doctrines. A 102 rejection applies regardless of ownership, meaning that even a third party’s prior disclosure can bar a patent application under this statute. Conversely, a statutory double patenting rejection arises only when the earlier patent and the second patent are commonly owned or share at least one inventor. Another major distinction lies in the use of terminal disclaimers. While both statutory double patenting and 102 rejections serve to prevent improper awards of patent rights in the same invention that has already been patented, their legal bases are different.

Application of Statutory Double Patenting

The application of statutory double patenting is very straight forward, as the claims have to include the same elements.  The rule prevents a second patent from issuing on the same subject matter.  No patent can be issued in the case of statutory double patenting, without exception. However, Section 101 does not address situations where there are slight modifications to the subject matter of the claim that do not add any patentable feature. The federal courts have developed the doctrine of obviousness-type double patenting to address these slight variations in subject matter between patent filings.

Nonstatutory Double Patenting: The Obviousness Basis

The nonstatutory double patenting rejection, also known as obviousness type double patenting, is a judicially created doctrine aimed at preventing a patent applicant from obtaining a second patent that merely claims an obvious variation of an earlier patent. The doctrine is grounded in an equitable principle that prevents an unjustified extension of the patent term.

Key Cases and Federal Circuit Decisions

Several key decisions by the federal appellate courts have shaped the doctrine of double patenting:

Miller v. Eagle Manufacturing Co., 151 U.S. 186 (1894) - The Concept of Double Patenting

In Miller v. Eagle Manufacturing Co., the Supreme Court set an early precedent by holding that an inventor cannot obtain a second patent on an identical claimed invention simply to extend patent rights. In this case, the patentee sought to secure an additional patent on a spring mechanism for improving plows or cultivators that had already been disclosed and claimed in an earlier patent. The court explained that allowing such a practice would unjustly prolong the inventor’s exclusive rights and contradict the purpose of the patent term limitation. This case remains a cornerstone in statutory double patenting jurisprudence, reaffirming that a patent must not grant more than one period of exclusivity for the same invention.

In re Vogel, 422 F.2d 438 (C.C.P.A. 1970) - Two Step Double Patenting Analysis

In In re Vogel, the court expressed a basic two step approach for analyzing double patenting issues: (1) if it is the same invention, Section 101 forbids a second patent, and (2) if a new claim of the application is no more than an obvious variation of the applicant's earlier patent, then the new claim is not patentable. The court was careful to point out that specification of the prior patent cannot be used as prior art. The double patenting rejection is not a prior art rejection, it is made based on the claims of the earlier patent, and cannot be based on the broader disclosure of the specification. The court found that Vogel was not claiming the same subject matter, but was merely extending the sausage making method of issued patent from pork to beef with a few obvious changes.

In re Schneller, 397 F.2d 350 (C.C.P.A. 1968)- Slight Modifications in the Claimed Invention Cannot Overcome a Nonstatutory Double Patenting Rejection

In re Schneller involved an application for a wire lathing clip used in construction. The applicant, Schneller, had already received a patent on a similar clip system and sought to claim a version that included a slightly modified lip structure. Schneller argued that his new claims were directed to a distinct and independent invention that was different from his earlier patent. Specifically, he contended that the addition of the lip structure created a patentably distinct improvement. The court explained that while Schneller’s new claims did add an additional structural feature, the claimed invention was still fundamentally covered by his prior patent. The court emphasized that the public interest in preventing the unjustified extension of the patent term outweighed any arguments that minor modifications justified a second patent. Importantly, the court noted that Schneller’s original patent claims were drafted broadly enough to encompass the improvements, meaning that granting a second patent would effectively extend the exclusive rights beyond the allowable term.

Gilead Sciences, Inc. v. Natco Pharma Ltd., 753 F.3d 1208 (Fed. Cir. 2014) - Double Patenting Rejection Based on a Later Filed Patent

In Gilead Sciences, Inc. v. Natco Pharma Ltd., the federal circuit reinforced the core of the double-patenting concept. An earlier-expiring patent was found to be a basis for an obviousness type double patenting rejection against a later-expiring patent, even though the later-expiring patent issued first. Gilead had obtained two patents—U.S. Patent Nos. 5,763,483 and 5,952,375—relating to antiviral compounds. The '483 patent issued before the '375 patent, but expired after it. Gilead sued Natco for infringing the '483 patent, and Natco defended by asserting that the '483 patent was invalid due to obviousness type double patenting over the earlier-expiring '375 patent.

Gilead argued that the '375 patent could not be used as a reference against the '483 patent because it was issued later. The Federal Circuit found that it could, emphasizing that the key policy concern of the judicially created doctrine grounded in double patenting is to prevent the unjustified extension of a monopoly beyond the expiration date of a patent.

The court explained that the proper inquiry should be based on the patent term, not the issuance date, particularly under the current America Invents Act patent system where expiration dates are determined by filing date rather than issue date. Allowing a later-expiring patent to claim an obvious variation of an earlier expiring patent would improperly extend exclusivity on claimed subject matter that should have entered the public domain.

Overcoming Double Patenting Rejections

Terminal Disclaimer

A common method to overcome a nonstatutory double patenting rejection—that is, an obviousness type double patenting rejection—is the filing of a terminal disclaimer under 37 C.F.R. § 1.321. A terminal disclaimer is a statement filed by the patent applicant voluntarily disclaiming any portion of the patent term that extends beyond the expiration date of an earlier patent. In addition, it must include a provision requiring that both the earlier and later patent remain commonly owned for their entire enforceable lives. The terminal disclaimer is intended to ensure that the patentee does not enjoy unjustified extended protection for obvious variations of the same inventive concept. When accepted, it effectively neutralizes the double patenting rejection by aligning the expiration dates of the patents in question and tying their enforceability to common ownership.

The use of terminal disclaimers is primarily intended as an equitable measure that prevents patent term extensions for related inventions that are not patentably distinct. However, it does not apply to statutory double patenting rejections, which are based on claims to the same invention. In such cases, a terminal disclaimer is ineffective because the law prohibits issuance of two or more patents for one invention regardless of term alignment.

Divisional Applications and Restriction Requirements

A significant statutory safeguard against double patenting rejections—particularly nonstatutory double patenting—is provided under 35 U.S.C. § 121, which applies to divisional applications filed in response to a restriction requirement imposed by the U.S. Patent and Trademark Office. A restriction requirement occurs when the examiner determines that a single patent application contains claims directed to two or more inventions that are independent and distinct. In such cases, the examiner may require the applicant to elect one invention for continued prosecution in the original application. The applicant may then file a divisional application to pursue the non-elected claims.

Under § 121, if a divisional application arises from an examiner-imposed restriction and the claims in the divisional are consonant with the restriction groupings, then the divisional application is protected from a nonstatutory double patenting rejection based on the parent application or any sibling divisional. This statutory protection acknowledges that the filing of multiple applications was not the result of applicant manipulation, but rather a procedural necessity imposed by the patent office. Importantly, the protection only applies where the claimed subject matter in the divisional maintains consonance with the restriction—i.e., it does not cross over or recombine elements from different groups that were originally required to be restricted.

However, this safe harbor does not apply to statutory double patenting rejections, which are predicated on the existence of identical claims. Moreover, if the applicant files what is effectively a voluntary divisional—one not based on a restriction requirement—or if the claims in the divisional diverge materially from the originally restricted invention, the safe harbor will not apply, and the applicant may face a obviousness type double patenting rejection.

Obviousness Analysis and Prior Art Considerations

In response to a nonstatutory double patenting rejection, a patent applicant may seek to overcome the rejection by demonstrating that the claimed invention in the later application is patentably distinct from the claims of the earlier patent. This is typically done through a detailed obviousness analysis, analogous to the approach taken under 35 U.S.C. § 103. The applicant must argue that the subject matter of the rejected claims would not have been obvious to a person of ordinary skill in the art at the time of the invention, in light of the claims of the reference patent, potentially in combination with secondary references or prior art.

These arguments may focus on structural, functional, or methodological differences that confer unexpected results, enhanced properties, or additional features not taught or suggested by the earlier claims. For example, if the later claims include elements not found in the earlier claims and those elements are shown to produce a synergistic effect or solve a problem unaddressed by the prior disclosure, the applicant may assert that the two inventions do not share the same inventive concept. In support, applicants can submit affidavits, technical declarations, or literature references demonstrating the non-obvious nature of the later claims. If successful, such arguments can preserve the full scope and term of the later-filed application without the need for a terminal disclaimer.

Addressing a non-statutory double patenting rejection can have drawbacks. Arguing against the scope of the claims in the patent used as the basis for a nonstatutory double patenting rejection can require the assertion that the earlier claims are narrow or limited. This may unintentionally weaken the enforceability or value of that earlier patent. Making negative statements about the scope or breadth of the first patent's claims could be used by third parties, including patent infringers, to undermine or avoid liability under the earlier patent. Such arguments may also be viewed as inconsistent or contradictory, potentially affecting credibility during prosecution or future litigation.

Distinction Between Obviousness Type Double Patenting Rejections and Section 103 Obviousness Rejections

An obviousness rejection under 35 U.S.C. § 103 and an obviousness-type double patenting rejection both concern whether a claimed invention would have been obvious to a person having ordinary skill in the art, but they differ in statutory basis, reference sources, and available responses. A § 103 rejection is based on prior art—typically published patents and patent applications having an earlier priority date, or printed publications—existing before the effective filing date of the claimed invention. In contrast, an obviousness-type double patenting rejection is a judicially created doctrine designed to prevent the unjustified extension of exclusivity for obvious variations of a previously claimed invention and is based on the claims of the applicant’s own earlier patent or commonly owned application, not on prior art per se.

To overcome a § 103 rejection, the applicant may argue that the references do not teach or suggest the claimed combination, or that the differences would not have been obvious due to secondary considerations (e.g., commercial success, unexpected results). In contrast, to overcome an obviousness-type double patenting rejection, the applicant may either amend the claims to make them patentably distinct from the earlier claims or file a terminal disclaimer aligning the expiration date of the later patent with the earlier one and ensuring common ownership throughout their terms.

Relationship Between Double Patenting and Patent Term Adjustment

The federal circuit has consistently held that a patent term adjustment (PTA) cannot be used to extend the expiration date of a patent when a terminal disclaimer has been filed in the application. Filing a terminal disclaimer results in the disclaimed patent expiring on the same day as the earlier patent to which it is terminally disclaimed, regardless of any PTA that might otherwise be available under 35 U.S.C. § 154(b). This rule reinforces the principle that a patentee should not receive an extended period of exclusivity for obvious variations of an existing invention simply due to administrative delays by the trademark office. Once a terminal disclaimer is on record, the disclaimed patent term is fixed and cannot be modified by later PTA calculations.

This strict limitation stands in contrast to the Novartis AG v. Ezra Ventures LLC decision, where the court upheld the enforceability of a proper patent term extension (PTE) under 35 U.S.C. § 156.

Novartis AG v. Ezra Ventures LLC, 909 F.3d 1367 (Fed. Cir. 2018) - Obviousness Type Double Patenting Does Not Override Statutory Patent Term Adjustment

The Novartis AG v. Ezra Ventures LLC, the Federal Circuit upheld the validity of a patent term extension (PTE) under 35 U.S.C. § 156, ruling that the doctrine of obviousness-type double patenting does not invalidate a properly extended patent. Novartis held two patents—the ’229 patent, which received a five-year PTE, and the later-filed but earlier-expiring ’565 patent. Ezra argued that the extended term of the ’229 patent unlawfully extended exclusivity over subject matter covered by the ’565 patent. The court rejected this, finding that § 156 authorizes a single patent extension per product, and the ’229 patent alone received the extension. The court reaffirmed that statutory PTEs cannot be invalidated by judicially created doctrines. Since only the ’229 patent was extended and the requirements of § 156 were met, the extension was valid, even if both patents were not patentably distinct.

Double Patenting in Joint Research Agreements

Under the America Invents Act (AIA), 35 U.S.C. § 102(c) replaced the pre-AIA statute 35 U.S.C. § 103(c) and provides that disclosures made by one party to a joint research agreement (JRA) will not be considered prior art against another party to the agreement under certain conditions. Specifically, if an invention is made by or on behalf of parties to a written JRA that was in effect before the effective filing date of the claimed invention, and the invention arose out of activities within the scope of the agreement, then the disclosure is not considered prior art under §§ 102(a)(1) or 102(a)(2).

Although § 102(c) directly addresses prior art rejections, its underlying policy rationale also informs treatment of obviousness type double patenting in collaborative research contexts. The USPTO has generally required common ownership to overcome a nonstatutory double patenting rejection, but where parties are subject to a qualifying JRA, they may achieve compliance through a terminal disclaimer that ensures both patents remain commonly owned or enforceable only during joint ownership.

In this context, applicants must ensure that the existence of a valid JRA is disclosed and that the claimed subject matter falls within the scope of the collaborative activities defined in the agreement. This approach enables related patents from different but collaborating entities to coexist without triggering an obviousness type double patenting rejection based solely on obviousness, provided they satisfy the procedural safeguards of the AIA and terminal disclaimer requirements. Accordingly, § 102(c) promotes innovation across institutional boundaries while preserving the core judicially created doctrine aimed at preventing unjust extensions of patent term through multiple patents on obvious variations of the same inventive concept.

Double Patenting in Reexamination Proceedings

Double patenting issues can also arise during reexamination proceedings, particularly where amended or newly presented claims are not patentably distinct from claims in a separate, earlier patent held by the same owner or commonly owned entity. Although reexamination is intended to reevaluate the validity of claims in view of prior art, the scope of the examination is not strictly limited to novelty and obviousness under §§ 102 and 103. The patent examiners may also consider double patenting rejections, especially where the reexamined claims appear to duplicate or represent obvious variations of those in another patent held by the same applicant or assignee.

In such instances, the Office may issue a nonstatutory double patenting rejection, requiring the applicant to demonstrate that the reexamined claims are patentably distinct from the reference claims in the earlier patent. The applicant may overcome the rejection either by amending the claims to introduce meaningful distinctions or by filing a terminal disclaimer to align the expiration date of the reexamined claims with that of the related patent.

The risk of double patenting rejection in reexamination highlights the need for applicants to carefully coordinate claim strategy across a portfolio of related patents, particularly when pursuing parallel or serial protection on the same inventive concept. Where patents are subject to continuation, divisional, or improvement filings, or are being reexamined concurrently with prosecution of related applications, the potential for conflicting claims and double patenting scrutiny increases. Clear claim differentiation and careful portfolio management should be employed to maintain enforceability and avoid obviousness type double patenting rejections.

Conclusion

Double patenting rules protect against the unlawful extension of the patent grant beyond the twenty years allowed by US patent law. Patent owners should be aware of this restriction and understand that the patent grant has a limited life span. Claiming small changes to a patented technology are unlikely to extend the patent protection beyond the twenty year term. It is equally important to understand that your important products and technologies can be covered by claims of different scope in order to provide protection against as many potential design arounds that a third party might conceive. While these different claims expire together, they provide more comprehensive patent protection, even those that may be subject to a nonstatutory double patenting rejection.

© 2025 Sierra IP Law, PC. The information provided herein does not constitute legal advice, but merely conveys general information that may be beneficial to the public, and should not be viewed as a substitute for legal consultation in a particular case.