Academics Weigh In On Efficacy of Pending Legislative Efforts To Combat “Patent Thickets” in the U.S
New York, NY, October 21, 2025
Peer-reviewed academic analyses have shown that patent thickets have significantly delayed the entry of less-costly generic drugs and biosimilars in the U.S. versus other highly-regulated markets like the EU and UK.[1] These studies have shown that the growth of patent thickets in the U.S. and their relative unavailability under European patent laws is a main reason why Europe sees lower prices for drugs and biologics sooner than in the U.S.
A new peer-reviewed study has weighed in on the relative expected effectiveness of various legislative remedies to the patent thicket problem that have been proposed or advanced during the Trump administration. This study, published by Sean Hu et al. in Health Affairs, [2] compares three competing approaches: (1) The “Affordable Prescriptions for Patients Act” (APPA), sponsored by Senators John Cornyn (R-TX) and Richard Blumenthal (D-CT), which would limit the number of patents that could be asserted in patent infringement litigation against biosimilars; (2) the “Eliminating Thickets to Increase Competition Act” (ETHIC Act), sponsored by Representative Jodey Arrington (R-TX) and Senator Peter Welch (D-VT), which would limit the number of continuation patents that could be asserted in litigation against generic drugs or biosimilars; and (3) a new USPTO rule proposed in 2024, since withdrawn, limiting the enforceability of continuation patents. The study concludes that the Cornyn-Blumenthal approach is unlikely to provide any meaningful relief to patients and end-payors in the U.S., while the approaches taken in the ETHIC Act and USPTO rule are more likely to significantly curtail the harms caused by patent thickets. These conclusions are summarized below.
- Affordable Prescriptions for Patients Act
As originally framed, the Cornyn-Blumenthal approach to limiting patent thickets would have substantially restricted the number of patents that a reference product sponsor (i.e., the originator company) could assert in district court patent infringement litigation seeking to bar a competitor’s biosimilar from the U.S. market. However, numerous “carve outs” were added to the bill in 2019 at the behest of PhRMA, a lobbying group funded by brand manufacturers, that effectively neutered its restrictions. The revised bill caps the number of patents that can be litigated at 20, which is more than the average number of patents typically asserted against biosimilars in district court. The cap also does not apply to multiple categories of patents that are often the focus of litigation against biosimilars. Patents that are filed before FDA approval of the brand product or within four years after approval are also excluded from the cap. Further, the cap may not apply in cases where the originator has alleged that the biosimilar failed to comply in full with the so-called “patent dance,” which is a complex, pre-suit exchange of information laid out in the U.S. biosimilar statute—an allegation made in over 90% of litigations brought against biosimilars. Finally, the APPA does not apply to generic drugs. With so many exclusions and loopholes, the APPA is unlikely to lower the number of patents that may be asserted against biosimilar and generic drug manufacturers, and thus will not curtail the incentives that brands currently have to amass and enforce such thickets.
- The ETHIC Act
The ETHIC Act would apply to both generic drugs and biosimilars, and would substantially limit the number of “continuation patents” within a thicket that the originator could assert in a given litigation.[3] A continuation patent is one that makes minor, obvious changes to the claims of an earlier-granted patent. These obvious variants often form the bulk of patent thickets, filed primarily to raise the cost of defending against claims of infringement. The ETHIC Act would limit the originator to asserting just one continuation patent from among its family of obvious variants, i.e., just one patent per inventive feature. The study’s authors conclude that it would protect legitimate innovation, including incremental improvements to old drugs, but would substantially restrict the ability of an originator to increase the cost and time needed to resolve litigation by asserting large numbers of duplicative patents.
- USPTO Rulemaking
In 2024, the USPTO proposed a new rule that was focused on limiting the number of continuation patents that could be amassed into a thicket. Under this rule, if a patent claim was found to be invalid, all subsequently filed continuation patents related to the invalid patent claim would become unenforceable. The goal was to reduce the incentive for originators to amass patent thickets in the first place. Hu et al. concluded that “the rule could have helped deter brand companies from obtaining continuation patents that are vulnerable to challenge since these challenges could result in the invalidation of numerous other patents.” The rule was withdrawn in December 2024 “after the [patent] office reported that it lacked the resources to support the proposed rule.” But Hu et al. proposed that enshrining the rule in Congressional legislation would overcome internal and external pressure to abandon the rule.
- Conclusion
Hu et al. ultimately conclude that “[p]assing the Affordable Prescriptions for Patients Act would serve more as window dressing than true reform; it would have limited effect on reducing patent thickets.” In contrast, “a combination of ETHIC and a legislative formulation of the USPTO rule” would “reduce existing pharmaceutical patent thickets and prevent future thickets from forming.” Given the glaring limitations of the APPA as amended, Congress should resist the temptation to pass that legislation and declare victory over patent thickets, and instead take a closer look at how thickets actually delay generic and biosimilar entry, and focus on fixes that would provide real relief without unduly restricting the patenting of legitimate incremental innovation.
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[1] Biological patent thickets and delayed access to biosimilars, an American problem | Journal of Law and the Biosciences | Oxford Academic
[2] Combating Pharmaceutical Patent Thickets In The Trump Administration | Health Affairs
[3] Text – H.R.3269 – 119th Congress (2025-2026): ETHIC Act | Congress.gov | Library of Congress