Contradicting rulings of the US patent office on double patenting jeopardize the generic and biosimilar drugs

ABSTRACT

Obviousness-type double patenting is allowed only in the US, but only if a terminal disclaimer and the same ownership are made for the expiry of the patent. Historically, this provision has hampered the entry of generic and biosimilar drugs due to the legal complexity and cost burden of resolving patent thickets accumulated by the originator companies. The United States Patent and Trademark Office (USPTO) proposed a change in the ruling in March 2024 to avoid double patenting if the patent to which it is tied in terminal disclaimer has any claims that have been invalidated as anticipated or obvious. This rule change aimed to promote innovation and competition by deterring strategies that leverage multiple patents for obvious variants to obstruct competitors. However, after receiving 349 comments on the proposed rule change, the USPTO withdrew its plan in December 2024 despite most comments favoring it. In a contrary move, the USPTO secured a court ruling that the terminal disclaimers do not apply to extended patent expiry due to the failure of the USPTO to prosecute a patent on a timely basis. The double patenting must end to enable more affordable generic and biosimilar drugs.

1. Introduction

In the United States, a single invention can give rise to a family of hundreds of patents [1], mainly due to the judiciously made doctrine of “double patenting,” where a patent applicant may file additional patents on numerous obvious variations of an invention. Courts have created two types of double patenting. “Same invention” double patenting prevents multiple patents on the same thing. The second is “obviousness-type” double patenting, which concerns obvious variants of the claimed invention [2]. The applicant just needs to agree that all these patents will expire simultaneously by filing a “terminal disclaimer” agreeing to forego the end of the term of the later-to-expire patent [3].

The proliferation of multiple patents on obvious variants of the same invention contributes to the problem of patent thickets, significantly increasing the transaction costs of searching, licensing, or litigating patents. This practice is particularly problematic because examiners often mistakenly grant invalid patents [4], and these invalid patents have real costs, particularly in the pharmaceutical industry [5]. Half of the patents listed with the Food and Drug Administration (FDA) to block entry of generic drugs have had terminal disclaimers, suggesting that they were obvious variants of the same invention; the same is the case for biosimilars [6]. Each new patent listed with the FDA imposes an additional barrier to entry by competitors. For example, granted patents can only be challenged one at a time at the USPTO, and a single patent typically costs over $40,000 in USPTO filing fees [7], plus another $500,000 or more in legal fees [8].

Double patenting is growing, with terminal disclaimers now being filed for over 15% of all patents, over 50% of litigated patents, and over 60% of patents covering FDA-approved drugs [1,9]. The proliferation of patents on slight variations of the same invention has increased the burden on patent examiners and the costs to innovative firms of evaluating, licensing, and litigating existing patents. Reducing abuses associated with double patenting by preventing unjustified term extensions and lowering the costs of challenging invalid patents makes good policy sense.

The problem of challenging every patent is particularly significant in the pharmaceutical industry. The Hatch-Waxman Act triggers a 30-month delay of generic market entry unless and until the generic can show that every patent listed on the FDA’s Orange Book has either expired or has been proven invalid or not infringed [10]. That regulatory regime means that pharmaceutical companies can often profit from listing multiple patents even if those patents are invalid because they will delay generic entry until every patent has been invalidated. The life science companies often file a flurry of double patents once their data exclusivity ends, hoping to extend their control period. Double patenting was particularly common in the pharmaceutical industry. However, the problem is not limited to the life sciences [11].

2. Background

Double patenting is handled differently by patent offices worldwide, reflecting legal principles and enforcement mechanisms variations. The European Patent Office (EPO) prohibits double patenting, ensuring that a patentee cannot secure multiple patents for identical inventions. While not explicitly codified, this principle is enforced through the European Patent Convention, requiring applicants to amend or withdraw overlapping claims, including those in divisional applications. In contrast, the USPTO addresses double patenting through the doctrine of obviousness-type double patenting (ODP), allowing the resolution of such issues by filing a terminal disclaimer. This ties the term of a latter patent to an earlier one and ensures common ownership, providing more flexibility than the EPO.

The UK Intellectual Property Office (UKIPO) and the Canadian Intellectual Property Office (CIPO) similarly prohibit double patenting but lack mechanisms like terminal disclaimers. Instead, overlapping claims must be resolved through amendments or withdrawals. Japan explicitly bans double patenting under Article 39 of its Patent Act, requiring applicants to revise or abandon applications with overlapping claims. For international applications filed under the Patent Cooperation Treaty (PCT), respective offices address double patenting during the national phase, necessitating compliance with local laws through claim amendments.

These differences create challenges for global patent strategies. With its allowance for terminal disclaimers and flexibility in divisional applications, the US approach contrasts sharply with the stricter prohibitions in jurisdictions like the EPO and JPO. This divergence often leads to strategic considerations when managing overlapping patent claims across different regions, particularly in cases involving issues like Patent Term Adjustment (PTA) extensions in the US. The variations underscore the complexity of harmonizing patent protection strategies worldwide while adhering to the unique requirements of each jurisdiction (Table 1).

Table 1.

Global intellectual property agency guidelines on double patenting.

Agency	Double Patenting Prohibition	Resolution Mechanism	Terminal Disclaimer Allowed	Treatment of Divisional Applications
EPO (European Patent Office)	Yes. Based on Articles 125, 54, and 84 of the EPC.	Amend claims or withdraw applications.	No	Must have distinct claims from the parent.
USPTO (United States)	Yes. Obviousness-type double patenting (ODP) addressed.	Terminal disclaimers, claim amendments.	Yes	Allows flexibility; ODP may apply.
UKIPO (United Kingdom)	Yes. Prohibited under the UK Patents Act 1977.	Amend claims or abandon applications.	No	Claims must not overlap with the parent application.
CIPO (Canada)	Yes. Addressed via case law.	Amend claims or voluntarily withdraw.	No	Requires clear distinction from the parent.
JPO (Japan Patent Office)	Yes. Explicit under Article 39 of the Patent Act.	Amend claims or abandon applications.	No	Divisional claims must be distinct from the parent.
PCT (World/International)	Yes. Handled during the national phase by local offices.	Amend claims to comply with local laws.	N/A	Subject to the rules of the national phase office.

3. The USPTO rules

Even if there are valid reasons, double patenting presents several policy concerns. Historically, the primary concern has been the worry that patent owners would improperly use multiple patents to extend their patent life. This was a particular worry for patent applications filed before 1995 because those patents lasted not for 20 years from the filing date but for 17 years from the issue date [12]. That meant that a continuation filed much later in the process would be issued and expire much later, creating the risk of a significant patent term extension. Indeed, many people abuse the process of extending their patent term significantly. That is less of a problem today when patents nominally expire 20 years after they are filed, but it is still a risk. More precisely, a US patent expires 20 years after the earliest nonprovisional application to which it claims priority, subject to various adjustments and limitations; See 35 U.S.C. § 154. Double patenting can apply to applicants who do not share this same earliest priority date. Thus, the overlapping patents may not have been filed simultaneously.

Courts created two types of double patenting rules to address this concern. First, it is “same-invention” double patenting: you cannot patent the same thing twice. That prohibition is absolute, but it is also very narrow. If there is anything less than complete overlap between the patent claims, it is not same-invention double patenting.

The second type: “obviousness-type double patenting,” also known as “nonstatutory double patenting,” wherein an inventor cannot patent obvious variants of their existing patent claims [13], noting that obviousness-type double patenting is intended to “prevent the extension of the term of a patent … by prohibiting the issuance of the claims in a second patent not patentably distinct from the claims of the first patent”) [14] unless they file a “terminal disclaimer.”

The USPTO offers flexibility in addressing double patenting by using terminal disclaimers, which provide patentees with more options to manage overlapping claims compared to the stricter prohibitions enforced in other jurisdictions. In contrast, the European Patent Office (EPO) and the Japanese Patent Office (JPO) strictly prohibit double patenting and do not permit mechanisms such as terminal disclaimers, requiring that claims in related applications be distinct. For applications filed under the Patent Cooperation Treaty (PCT), double patenting is handled during the national phase and is subject to the specific rules and practices of the respective national patent offices, resulting in variations in how the issue is resolved.

The US Patent Act provides that an inventor may obtain “a patent” (35 U.S.C. § 101). However, it is common for inventors to obtain multiple patents stemming from the same basic idea. Indeed, a significant fraction of all patents issued in the United States belong to “families” of more than one patent.

3.1. Divisional

Inventors can obtain overlapping patents in several ways, but not all are problematic. Sometimes, inventors include more than one invention in the same application. When they do, the USPTO will issue a “restriction requirement” compelling the applicant to split their application into different prosecutions for each invention (35 U.S.C. § 121). These split applications, called “divisionals,” are not separate patents on the same invention. Instead, they indicate two or more patentably distinct inventions in the same original application.

3.2. Continuation

A second, more common, way to obtain multiple patents is to file a “continuation” application. Curiously, current rules do not permit the USPTO ever finally to reject a patent application. The applicant is always entitled to come back and try again [15]. One way to do that is by filing a “continuation” application. As its name suggests, a continuation application continues prosecution. But if the applicant just wants to fight with an examiner who refuses to grant a patent, there is a quicker and simpler way to do that: a “request for continued examination” (RCE) (35 U.S.C. § 132(b); 37 C.F.R. § 1.114). Continuations, by contrast, allow the patent applicant to obtain a patent on some claims of the invention and to continue prosecuting the patent to obtain a second (or third, or fourth, or hundredth.) Some rogue patentees have obtained many – even hundreds – of patents from the same application, Hyatt v. Hirshfeld [16], where Hyatt filed 381 applications on the same day as photocopies of 11 prior parent applications; during prosecution, he filed 115,000 claims based on those original applications). In the case of Symbol Techs., Inc. v. Lemelson Med [17], Lemelson obtained 16 patents claiming machine vision and dozens of other patent applications based on two applications filed as many as four decades earlier, the court noted that at the time of litigation, Lemelson occupied all of the top 13 slots for the patent applications that had spent the longest in prosecution). And many of the most prolific inventors obtain multiple patents per application. Of the 100 most prolific inventors based on U.S. patents granted, only eight obtained no more than one patent per application, and seven of those eight did so decades ago before continuation practice was established [18]. By contrast, Lee Whetsel of Texas Instruments obtained 828 patents based on 128 applications, an average of more than six patents per application [19].

Continuation practice (and therefore double patenting) is quite common. One recent empirical study found that more than 15% of all patent applications filed in 2018 were continuations [20], and the USPTO reports that continuation applications tripled from 2010 to 2022 and are now 34% of serialized filings [7]. Thus, a significant fraction of issued patents are likely duplicative of another issued patent. That number is significantly higher for important categories of patents. For instance, this continuation practice is more common among standard-essential patents, with 46% of SEPs coming from a continuation application [20]. Similarly, 47% of patents listed for FDA-approved drugs from 2000 to 2015 are continuations [9].

Pharmaceutical companies are frequent users of multiple-continuation strategies. AbbVie, for instance, filed a chain of 22 continuations based on a single patent application for its drug Humira [21].

Patents litigated in cases terminated 1999–2000 come from a family of 1.85 patents from the same application, on average, compared with a family size of 1.22 patents for non-litigated patents [22].

3.3. Overlap

Continuations are not the only way to obtain multiple patents stemming from the same basic idea, though they are the primary ones. It is also possible to file two patent applications with overlapping claims so that one patent would invalidate the other without an exception. Sometimes, the same inventors file two applications on the same day so that neither is prior art to the other, though they may produce multiple patents on the same invention. Sometimes, they file patent applications on different days, but for at least 2.5 years when the first is not prior art against the second. Sometimes, they file different patent applications because while the same group worked on an invention, the patents are attributable to other (albeit overlapping) “inventive entities” (Pre-AIA § 102(b)).

Under the current novelty statute, a first patent application is a prior art against a second application with overlapping inventors only 1 year after the first application is published, see 35 U.S.C. § 102, and publication often occurs 1.5 years after filing. Still, it may be delayed until the first application issues [§ 122(b)]. The patent novelty statute was substantially amended by the 2011 America Invents Act (AIA) [23]. Patents filed before 16 March 2013, are governed by the pre-AIA statute, under which an earlier patent application is prior art as of its filing date only if it is both (1) filed “by another” (i.e., not the same combination of inventors) and (2) filed before the invention date (not the filing date) for the second application. 35 U.S.C. § 102(e) (2010) [hereinafter Pre-AIA § 102]. Thus, a pre-AIA patent application will be prior art against a later application by the same inventor only if it is published before the second invention date, see Pre-AIA § 102(a), or more than 1 year before precedent did not permit naming as an inventor a person who did not contribute to all the claims of the patent.

3.4. Inventors

Patent law treats each unique combination of individuals as a separate inventive entity, even if they all work for the same company and work together on the same project. Thus, if Smith and Lee developed a particular device in their lab and then Smith, Lee, and Alvarez made a minor change to that device, only Smith and Lee are the inventors of the unaltered device, while all three inventors of the altered device. That historically meant they had to file separate patent applications, though more recent statutory changes have reduced the need for that.

In addition to solving the problem of different inventive entities, patent owners can use double-patenting for other valid reasons. For example, pharmaceutical companies frequently seek a patent on a class of drugs they are testing and on the formulation they submit for FDA approval. Sometimes, those claims end up in separate patents for innocuous reasons. For instance, it may be harder to persuade the USPTO to grant the broader genus claim patent, and the company may accept the patent on the narrower claim while continuing to press for the broad claim in a continuation application.

3.5. Terminal disclaimer

Terminal disclaimers have been employed to address the issue of double patenting, ensuring that inventors cannot unfairly extend the life of their patent protections. A terminal disclaimer is an agreement binding two related patents to expire simultaneously based on the earlier patent’s expiration date. This tool helps prevent the improper extension of a patent’s term. It ensures that overlapping patents are enforceable only when owned by the same entity or jointly under a research agreement (37 C.F.R. § 1.321(c)(3), (d)(3)).

Unlike same-invention double patenting, which requires identical inventors for identical inventions, obviousness-type double patenting involves closely related inventions that may have different but overlapping inventors. Terminal disclaimers address this by allowing patents with shared inventors, owners, or joint research agreements to co-exist without extending exclusivity unfairly. However, if there is no overlap between inventors and owners, the latter patent is invalid, as evident earlier.

Courts have reinforced using terminal disclaimers to prevent deception in extending patent terms. In Gilead Sciences v. Natco Pharma, the court ruled that terminal disclaimers apply to the patent with the later expiration date, irrespective of filing or issue dates, to prevent manipulation of exclusivity periods [24]. Similarly, in AbbVie, Inc. v. Mathilda & Terence Kennedy Institute of Rheumatology Trust, concerns about orchestrating longer exclusivity periods through strategic filing [25].

Recent developments, including the Federal Circuit’s Cellect decision and the USPTO’s proposed updates to terminal disclaimer regulations, aim to address two additional challenges. First, patent term adjustment (PTA), a mechanism to compensate for USPTO delays, has been exploited by patent owners to extend exclusivity by filing multiple patents on obvious variants of the same invention. This often results in some patents starting earlier and others receiving extended terms due to PTA. Although the exact number of such cases is unclear, empirical evidence shows that many patents with terminal disclaimers have benefited from PTA extensions.

Second, the proliferation of patents within the same field, even if they expire simultaneously, creates significant social and economic costs. The growing number of continuing applications and double patenting cases strains USPTO resources and increases the likelihood of errors, leading to “patent thickets.” These thickets make challenging patents and discourage competition harder and more expensive. While the USPTO’s Patent Trial and Appeal Board (PTAB) offers a lower-cost alternative to court challenges, with proceedings costing around $500,000 compared to $5 million in court, each patent requires a separate challenge (23). Courts also limit the number of patents or claims that can be litigated in a single proceeding, compounding the difficulty.

The accumulation of overlapping patents skews the calculation of royalties for standard-essential patents (SEPs), often based on the number of patents involved. Additionally, it hinders antitrust challenges against monopolistic behaviors, as courts require proof that all possible patents in a thicket have been challenged. These issues highlight the need for regulatory reforms to balance innovation incentives with fair competition and manageable enforcement mechanisms.

4. Fixing the double patenting dilemma

The USPTO has taken two significant actions: one that restricts the impact of double patenting by refusing to accept the patent extension to apply to double patenting, an incorrect and unethical decision, refusing to take responsibility for the delay caused by the functionality of the USPTO that had awarded extent patent life; the second one to limit the use of terminal disclosure when the claims are invalidated, but this was withdrawn. Both decisions are wrong, requiring the USPTO to take a more logical and ethical road to address the anomaly of double patenting unique to the US.

4.1. In re cellect

Recently, two key institutions in US patent policymaking – the Federal Circuit and the USPTO – have taken steps to limit the power conferred by multiple patents. In 2023, the Federal Circuit held in In re Cellect that double patenting requires patents to expire on the same day under a terminal disclaimer, even if one has received a Patent Term Adjustment (PTA) extending its term beyond 20 years term [26].

This decision highlights a legal conflict between PTA, which compensates patentees for USPTO delays, and the doctrine of obviousness-type double patenting (ODP), which prevents unjust extensions of monopoly through patents with indistinct claims. Despite the statutory purpose of PTA, the Federal Circuit ruled that PTA-extended expiration dates must be included in ODP analysis, leading to Cellect’s patents being invalidated due to overlaps with earlier family patents.

Cellect argued that delays caused by the USPTO should not penalize patentees under ODP and that PTA, like Patent Term Extensions (PTE), should be excluded from ODP analysis. The Federal Circuit rejected these arguments, affirming that ODP applies regardless of the cause of differing expiration dates. After the Federal Circuit denied rehearing in January 2024, Cellect appealed to the Supreme Court, asserting that this ruling unjustly negated the benefits of PTA and could cost US biopharma and technology innovators billions of dollars. However, on 7 October 2024, the Supreme Court declined to review the case, leaving the Federal Circuit’s decision intact [27]. This outcome underscores a paradox wherein PTA, intended to address USPTO inefficiencies, can be overridden by ODP, creating uncertainty for patentees relying on extended terms.

In its decision, the Federal Circuit clarified that PTA is included in patent term calculations for ODP, emphasizing that “ODP for a patent that has received PTA … must be based on the expiration date of the patent after PTA has been added.” However, the court left certain aspects of the PTA-ODP interplay unresolved. Specifically, it ruled that a first-filed, first-issued, later-expiring claim cannot be invalidated by a later-filed, later-issued, earlier-expiring reference claim, setting the maximum exclusivity period based on the first-issued patent. This leaves questions about when a patent claim may serve as an ODP reference.

Patentees are advised to revisit expiration dates of patents with PTA to address potential ODP issues, evaluate whether a patent with PTA qualifies as a first-filed, first-issued, later-expiring patent, and consider filing terminal disclaimers if appropriate. Additionally, patent prosecutors should account for PTA accrual during prosecution and its impact on continuing applications to minimize risks associated with ODP. These developments signal the need for careful management of patent portfolios to navigate the complexities of PTA and ODP in the evolving US patent landscape.

After the Federal Circuit denied rehearing in January 2024, those urging the Supreme Court to take up the case have suggested that Cellect “is likely to cost [U.S.] biopharma and technology innovators billions of dollars” [28].

4.2. Defining double patenting limits

The USPTO took a significant leap when it published its plan to amend the rules in May 2024, requiring that a patent with a terminal disclaimer filed to avoid double patenting should not be enforceable if the patent to which it is tied has any claims that have been invalidated as anticipated or obvious [29].

The USPTO introduced a rule [29] to overcome obviousness-type double patenting rejections on 10 May 2024; details of this proposed change are listed in Table 1. The table below summarizes the current rulings and proposed rulings related to nonstatutory double patenting and clarifies the intentions of the proposed changes (Table 1).

The objective is to prevent the misuse of terminal disclaimers in enforcing multiple patents on apparent variations of an invention, particularly when one of the patents in the chain is invalidated. To achieve this, the mechanism requires terminal disclaimers to include enforceability conditions that link the validity of claims across all patents tied together by such disclaimers. This approach aims to promote fair competition and uphold the integrity of the patent system by making it more challenging to exploit nonstatutory double patenting rules for undue advantage (Table 2).

Table 2.

USPTO current and proposed rulings on double patenting.

Aspect	Current Rulings	Proposed Rulings
Requirement for Terminal Disclaimer	Terminal disclaimers are required to overcome nonstatutory double patenting, ensuring common ownership and patents expire simultaneously.	Adds a requirement that terminal disclaimers include an agreement ensuring the enforceability of the patent is contingent upon it not being tied, directly or indirectly, to another patent invalidated or disclaimed based on anticipation or obviousness.
Impact of Invalidated Claims	Current rules do not explicitly address the enforceability of patents tied by terminal disclaimers if one patent’s claim is held invalid.	Any patent tied through terminal disclaimers to a patent whose claims are invalidated or disclaimed would also be unenforceable.
Purpose of Terminal Disclaimer	Prevents unjustified extensions of patent terms by requiring common ownership and simultaneous expiration of related patents.	Extends this purpose to prevent enforcement of patents tied to another patent deemed invalid, thereby deterring multiple patents for obvious variants and promoting competition and innovation.
Effect of Final Invalidity Ruling	No direct link between the enforceability of related patents and the invalidation of claims in one patent.	Proposes to render all patents tied by terminal disclaimers unenforceable if a court or the USPTO invalidates or a statutory disclaimer is filed for a claim based on anticipation or obviousness.
Scope of Change	Focuses on ownership and term synchronization without addressing competitive concerns arising from invalidation.	Targets competitive and innovation concerns by eliminating the enforceability of all tied patents, preventing abuse of the system for obvious variants.
Rationale	Ensures administrative simplicity and fair expiration terms for related patents.	Promotes innovation and competition by deterring strategies that leverage multiple patents for obvious variants to obstruct competitors.

This proposal has met with 11 oppositions filed from Johnson & Johnson, AbbVie, Novartis, and others claiming disruption of settled expectations for research investments [26]. However, this proposed rule change was recalled on 4 December 2024 [30] after receiving 349 comments during the 60-day comment period [31] concluding that it would bring higher cost constraints to originator companies, favoring big pharma, even though only 52 out of 349 comments had opposed the rule change. Table 3 lists the 52 who opposed the rule change, and while 298 were in favor, the USPTO decided in favor of those who opposed it (Table 3)

Table 3.

The 52 comments that opposed the rule change.

Celia Leber; American Bar Association Intellectual Property Law Section; Japan Pharmaceutical Manufacturers Association; Stephanie Kwong; James Vetter; Canon Inc.; Carmichael IP and Kenneth J. Weatherwax; Innovation Alliance; Brandon Dube; Anonymous; Americans for Tax Reform; Qualcomm Incorporated; Allen Hoover; Nevro Corp; Patients For Affordable Drugs; Walter Phillips; EnQuanta, a VoiceIt Technologies Company; Clayton Howarth, P.C.; Advanced Medical Technology Association (AdvaMed); Patent Asset Management LLC; VENTUS THERAPEUTICS U.S., INC.; Dolby Laboratories; carol fletcher; Mark Syman; Deepak Malhotra; Alliance of U.S. Startups and Inventors for Jobs (”USIJ”); Cochlear Limited; IPValue Management, Inc.; Maf Holdings LLC; American Intellectual Property Law Association; Anonymous; Anonymous; Steven Hoffberg; Boston Intellectual Property Law Association; InterDigital, Inc.; Alfred Nugent; PTAB Bar Association; Unified Patents, LLC; Adeia Inc.; Andrew Berks; Tracy Neal; Fresenius Kabi, USA; Biotechnology Innovation Organization (BIO); Timothy Taylor; Nick Carbone; Daniel DiLorenzo; Meet LLC; Brian Boon; Matteo

While the rule change could have decreased competitors’ costs in seeking to challenge multiple patents on the same invention, such as biosimilar developers, the patent applicants or originators would likely have seen increased patent prosecution costs associated with choosing to argue against obviousness-type double patenting rejections, amending claims, or filing a terminal disclaimer. In other words, the decision of the USPTO to withdraw the rule change brings benefits to reference product companies and makes the development of generics and biosimilars more costly. It also promotes the disharmony of intellectual property rights across the globe, the US being the only country where double patenting for nonstatutory claims is allowed.

The USPTO had previously requested comments on double patenting, stemming from a Biden Administration Executive Order concerned with patents “unjustifiably delay[ing] generic drug and biosimilar competition” [32].

Under the proposed rule, new terminal disclaimers filed “to obviate nonstatutory [i.e., obviousness-type] double patenting” would have to affirm that the patent with the disclaimer will not be enforced if a patent to which it is tied (directly or indirectly) has a claim invalidated as anticipated or obvious.

Because the proposed rule would increase the incentive to avoid terminal disclaimers, critics have argued that it will raise patent prosecution costs by increasing challenges to double-patenting rejections [33]. However, even if patent owners change their behavior in response to this rule change, the net effect on prosecution costs seems ambiguous. Applicants will be more likely to file related claims together in the first place, so there will likely be less need for examiners to issue double-patenting rejections (or for applicants to pay terminal disclaimer filing fees).

This analysis failed to account for how the proposed rule will benefit small entities and other innovators. Innovators and entrepreneurs encounter the patent system through their patenting efforts and searching existing patents to determine their freedom to operate or defend themselves from (sometimes meritless) patent infringement lawsuits. The proposed rule would reduce these costs. For example, in one of the few positive comments on the rule so far, Garmin International notes that the invalidity of a patent on which it had filed an IPR petition was recently affirmed – and that the patent was the fifth continuation in its family [34]. Mercedes-Benz USA similarly comments that double-patenting practice leads to protracted litigation over weak patents because a patent owner can always obtain another continuation patent even after invalidating earlier ones [35]. Reducing the costs of challenging chains of related patents will disproportionately benefit the small entities for whom these costs are most salient.

The USPTO’s proposed rule thus makes good policy sense, but as about two-thirds of PTAB decisions invalidating a patent claim uphold other claims in the same patent [33], it creates an anomaly that must be removed.

5. Advice to USPTO

If the US patent law could be simplified by eliminating double patenting, it would make it easier for generic and biosimilar pharmaceutical companies to enter the market by removing a significant regulatory barrier that can rely even on clearly invalid patents. It would also make it easier and cheaper to resolve patent litigation for everyone.

The argument that eliminating double patenting would hurt innovation incentives by big pharma is inaccurate. The arguments opponents present relate to overlapping inventorship and the need to draft claims of different but overlapping scopes at various times. However, the overlapping inventorship problem has largely been solved by a series of statutory changes that made inventorship law less strict. Those changes culminated in the America Invents Act (AIA) [23], which allowed inventorship correction at any time and permitted patentees to obtain patents with overlapping inventors who work for the same company or even for different cooperating companies in a joint research relationship. The AIA, enacted in 2011, brought significant changes to US patent law, including a shift from a “first-to-invent” to a “first-inventor-to-file” system, and introduced several provisions to modernize the patenting process. One notable change under the AIA is the allowance for correction of inventorship errors at any time during the life of a patent, simplifying the process to ensure that patent documents accurately reflect the actual inventors. Additionally, the AIA permits patentees to obtain patents with overlapping inventors, even when those inventors work for the same company or different companies engaged in a joint research relationship. These changes facilitate collaborative innovation while clarifying patent ownership and rights, making the patent system more adaptable to modern industrial and research environments.

The overlapping scope concern requires multiple patents under current law, if it is desirable to allow an inventor to obtain a patent on, say, a particular chemical and then later obtain a patent on a whole class of chemicals, it is a part of. The latter patent would be invalid under current law unless the same inventors developed both. Allowing both patents provides patent owners an advantage, particularly in the life sciences industry. However, it is less clear how significant that advantage is, especially given the current difficulties in patenting broad genus claims.

Given uncertainties about the effects of patents more generally and the narrow nature of the claimed benefits of double patenting, a lot depends on who has the burden. A letter from a letter from five former USPTO Directors or Deputy Directors calling on the USPTO to withdraw its proposed rule “immediately” because it “threaten[s] serious harm to America’s innovation economy” [36]. And the Chamber of Commerce has decried the absence of reliable evidence on the extent of the problem [37].

One argument the former directors make that clearly cannot justify the current rule is the claim that “America is losing its technological edge to China,” we must strengthen US patent rights to avoid that result. That argument fails as a general matter. National patents are granted to inventors from any country, and a growing percentage of US patents are granted to Chinese nationals. For example, from 2012 to 2022, most US patent applications have been of foreign origin, and the percentage from China more than tripled, from 2.4% in 2012 to 8.2% in 2022 [38].

A claim that stronger patent laws will boost the US economy is ill-founded. It defeats the purpose of the patentability of inventions that are given a fixed time to benefit commercially if the period of 20 years from the filing of the patent is not sufficient to expand the innovation, then blocking others from competing defeats the primary purpose of the patent laws in the first place. At worst, it adds a substantial cost of challenging invalid patents that are harmful to the generic and biosimilar drugs that are supposed to bring cost normalization to patients; it is difficult to find any substance to the claim that removing double patenting will hurt the economy.

5.1. International harmonization

It is not recommended to harmonize the US patent laws with the law in jurisdictions such as the European Patent Office (EPO), Japan, and China. In these jurisdictions, patent applications are prior art for anticipation as of their filing date. Still, they are not prior art for obviousness (which they call “lack of inventive step”) until they are published 18 months after filing [39]. This means that anyone may “double patent” by patenting apparent variations of an earlier patent and extending the term of exclusivity with no equivalent to the US terminal disclaimer. While the harmonization appears to simplify the complex US law of double patenting, it would also be a step backward. In the 1965 case Hazeltine Research, Inc. v. Brenner, the US Supreme Court held that unpublished patent applications are prior art for obviousness and anticipation [39].

The ability for anyone to patent obvious variations of earlier patents in other jurisdictions has led to thickets of patents with different owners, creating licensing challenges for implementers – including the original patentee [39]. That is a risk considering the economic evidence that many of the most important inventions are independently developed by different parties around the same time [40]. Harmonizing US law toward these standards would exacerbate these concerns in the United States.

In addition, the problems created by double patenting in foreign jurisdictions are mitigated to some degree by limitations on foreign patent rights that do not exist in the United States. For example, the United States has a one-year “grace period” during which a patentee’s publications and other public activities are not prior art. In contrast, the EPO and China have a strict novelty requirement such that any publication or other public act immediately bars patenting [41]. Both jurisdictions offer only a six-month grace period in minimal circumstances, primarily aimed at deliberate copying of the invention by someone who then seeks to patent it

Other jurisdictions, such as Japan, also mainly do not allow continuation applications, although they do allow divisionals [42]. They also reduce the costs of thickets through more stringent examination, lower litigation costs and damages awards, and routine shifting of attorneys’ fees. Europe and many other countries lack a patent linkage system that explicitly ties generic marketing to something like the FDA’s Orange Book. Harmonizing US law with foreign practices along these dimensions would receive little support from US patent owners. But without those limitations, expanding double patenting would exacerbate the abovementioned problems.

5.2. Narrower reforms

While there is a case to be made for abolishing double patenting altogether, other options should be evaluated, such as allowing patent owners to have only one patent in force covering a given invention. Still, allowing them to elect to replace one patent with another that covers an obvious variant of the first. For instance, an inventor who obtained a patent on a particular chemical and then decided they wanted to claim a modified form of that chemical (such as an enantiomer) [40] could obtain a new patent on the enantiomer but only by forfeiting the claim to the existing patent. Requiring such an election would allow the patentee to decide to prefer the patent best suited to its products (or to block its competitor’s). Still, it would prevent them from asserting multiple patents to delay generic entry or raise the cost of breaking through a patent thicket.

An election system would likely require some fine-tuning. For instance, a patentee should not be able to assert a patent, lose it, and abandon it in favor of another, while still requiring a terminal disclaimer system to prevent the election from being used to extend the patent term.

An alternative would permit double patenting subject to a terminal disclaimer, but only where there was an explainable reason why the claims in the latter patent could not have been included in the earlier patent. In practice, this would likely mean allowing double patenting when applications were filed at different times (but still within the grace period) because the inventors had developed a different but obvious variant they had not invented when they filed the original patent application. By contrast, double patenting would not be allowed for patents stemming from the same application or from applications filed on the same day by the same or overlapping inventors since, presumably, the inventors could have included any claims in the original application. While a common reason in the past for double patenting was the problem of overlapping but non-identical inventive entities, current law has effectively solved that problem, as noted above.

Another way to solve both the problem of needing to add new claims to a patent and the problem of dealing with multiple patents is by barring double patenting, but changing the rules to allow new claims to be added to an existing patent, as Tu and Lemley have proposed [40]. This system comports with the end goal of using a terminal disclaimer – having the patent expires at a defined time – but without creating a second patent.

There is no statutory requirement that claims cannot be added to an existing patent. Indeed, the statute permits patents to be reissued with new claims. Sections U.S.C. § 251(a) and Section 251(b) provide that “[t]he Director may issue several reissued patents for distinct and separate parts of the thing patented, upon demand of the applicant, and payment of the required fee for a reissue for each of such reissued patents.” The reference to the applicant’s “demand” could be read to mean that the patentee can have multiple reissued patents if they want them. Still, the use of the word “may” suggest the better reading of the statute is that the USPTO has discretionary power to grant more than one patent, but only if the applicant asks for it. Customarily reissue practice is used to correct an error in the patent. However, an error can include things most people would not view as errors: changes driven “because of the patentee claiming more or less than he had a right to claim in the patent.” According to U.S.C. § 251(a).

Another solution to prevent firms from creating large patent thickets that are hard to challenge is to change the rules for the scope of IPRs to permit IPR challenges to include claims from related patent family members. This would allow generic firms to avoid the patent thickets created by brand firms. It can be made mandatory for the PTAB to consider all related patents when evaluating an IPR for a double patent, also in the court, requiring patentees to assert and courts to consider the validity of all related patents together in the same proceeding. To make IPRs useful in the pharmaceutical context, Congress would likely have to change the law to permit IPR invalidation to trigger the 180-day exclusivity given to the first ANDA filer. Currently, the IPR does not lift the stay on generic entry [2]. The USPTO would likely also have to change its page limits to allow multi-patent IPRs in the specific context of Orange Book-listed patents.

6. Conclusion

The US is the only country allowing double patenting that harms generic and biosimilar drugs due to the high litigation cost and delays that discourage smaller companies from entering the field. There is no ground to conclude that limitations on existing US patent rights will deter innovation and harm the economy. The decision of the USPTO to pull out of the proposed amendment to the rules shows a significant weakness of the USPTO in responding to strong opposers, albeit in a smaller number. Similarly, the USPTO must take responsibility for its actions that delay patent prosecution if it allows the status quo of double patenting. Ideally, if double patenting is removed altogether, it will remedy both situations.

Funding Statement

The work was not funded.

Article highlights

• The US patent laws re-patenting an invention with modifications that is not allowed elsewhere the repatenting is abused by patent holders to extend their exclusivity beyond the patent period of 20 years from the data of first filing.

• Double patenting blocks generic and biosimilar drugs to enter and provide affordable options.

• US Patent Office decided to remove this clause through legislative changes but after getting extensive opposition by the big pharma, they withdrew this provision, essentially removing this possibility.

• The US Patent Office action is unethical and shows the power of big pharma in modulating US government regulations to their benefit.

• The US patent Office should bring that the double-patenting prohibition to help American patients, legally and ethically.

Disclosure statement

S.K.N. is an advisor to the US Senate, the FDA, and the White House; he is also a patent law practitioner and developer of biosimilars and other biological products. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.