By Jamie Chuvalo-Abraham, Ayla Misbah, Mags Martin, and Foha Nawaz
Drug manufacturers can use "patent thickets" to delay biosimilar market entry. Biologics, such as Humira, are complex drugs manufactured from living cells and typically given by injection or infusion. A biosimilar, such as Amjevita, is highly similar to an original biologic with no clinically meaningful differences; unlike a generic copy of a simple chemical drug, it cannot be an exact replica. Congress is now moving to address the practice. In July, the Senate unanimously passed the Affordable Prescriptions for Patients Act (APPA), which would limit how many patents a biologic manufacturer can assert against a biosimilar competitor. The bill has since been sent to the House.
The policy fight turns on a deceptively simple question: when does a portfolio of individually lawful patent rights become a competition problem? No product illustrates that question better than Humira, AbbVie's blockbuster autoimmune drug, which was protected by 132 additional patents beyond its original patent. This article explains how patent thickets form, then uses Humira to show how they work in practice, how courts treat them, and what reforms are on the table.
What is a patent thicket?
A patent thicket is a dense web of overlapping patents related to a single product or technology, often accumulated by a manufacturer to protect its market position. A company seeking to enter the market must navigate numerous, closely related patents rather than just one.
Thickets form because a single product can be protected by many types of patents. Beyond the original molecule or crystalline form, a drug manufacturer may patent the drug's formulation, dosing regimen, manufacturing process, medical indications, and delivery device.
The strategy of building patent thickets is not limited to medicine. Olaplex, the hair-care brand, reported approximately 100 granted patents worldwide covering its products and related technologies in its 2025 annual report. The company has described its patent portfolio as creating barriers to entry.
How thickets extend exclusivity
Thickets matter because they can prolong protection from competition. In theory, a patent grants the inventor a time-limited right to exclude. In practice, layered patents can restrict competition beyond the original patent's term, a practice known as "evergreening."
Consider a simplified timeline: a company's original patent has a term measured from a nonprovisional application filed in 2000, and it expires 20 years later, in 2020. Along the way, the company files a dosage patent in 2007 and a manufacturing patent in 2010. Assume those applications do not claim the benefit of earlier filings and that no term adjustments, extensions, or disclaimers apply. When the original patent expires, those later patents remain in force until 2027 and 2030, respectively, potentially restricting competitors that need to use the claimed dosing regimen or manufacturing process.
Another way companies may extend the lifetime of a patent is through patent term extensions. A patent term extension, which must be requested before the patent expires, can add up to five more years to compensate for time lost during regulatory review provided that the remaining patent term, including the extension, generally does not exceed 14 years from U.S. Food and Drug Administration (FDA) approval. Unlike patent thickets, statutory patent term extensions lengthen an existing patent's term.
Evergreening is especially significant for biologics like Humira. Because biologics are complex, each one can generate many patentable developments over time, from formulation to device, which is exactly the condition in which thickets grow.
Case study: Humira
Humira brings these pieces together, offering a real-world example of how patent thickets can delay biosimilar competition. In a 2022 opinion, the U.S. Court of Appeals for the Seventh Circuit noted that Humira's original patent expired at the end of 2016, but that AbbVie had obtained 132 additional patents related to the drug, the last of which was set to expire in 2034. Those 132 patents, obtained from 247 patent applications, cover Humira's formulation, device, dosing, manufacturing, and more.
Not every patent in the portfolio was a mere legal maneuver. For example, after patients complained about painful injections, AbbVie developed a citrate-free, high-concentration version of Humira that delivered the same dose in half the liquid volume and significantly reduced injection-site pain. According to biosimilar maker Celltrion as reported by The Hospitalist, AbbVie moved more than 80% of American Humira patients onto the new formula well before competitors arrived. By the time the first biosimilars launched in the United States in 2023, most patients had already left behind the original formula that many biosimilars copied. That dual character, part genuine innovation and part formidable barrier to competitors, is what makes Humira such a revealing case. This same tension is what the courts were asked to resolve.
Humira in court
That tension reached the Seventh Circuit in Mayor and City Council of Baltimore v. AbbVie, 42 F.4th 709 (7th Cir. 2022), an antitrust class action brought by indirect purchasers who were welfare-benefit plans that pay for Humira on behalf of their members. The plaintiffs argued that AbbVie was eliminating competition, while AbbVie argued that it was lawfully protecting its market from biosimilars. The Seventh Circuit affirmed the dismissal of the complaint.
The plaintiffs brought claims under both Section 1 and Section 2 of the Sherman Antitrust Act. Two doctrines framed the Section 2 analysis. The Noerr-Pennington doctrine treats petitioning the government as protected activity, subject to a "sham" exception that, for litigation, requires both objective baselessness and an intent to use the process itself to interfere with a competitor. The Walker Process doctrine provides that enforcing a patent obtained through intentional fraud on the U.S. Patent and Trademark Office (USPTO) can support antitrust liability when the other elements of monopolization are met. The plaintiffs, however, did not rely on the Walker Process doctrine, which the court said made it hard to see how AbbVie could be penalized for its successful patent applications.
Under Section 1, the plaintiffs alleged that AbbVie's settlements with biosimilar manufacturers amounted to "reverse payments," a pay-for-delay tactic. They alleged that earlier European entry compensated biosimilar manufacturers for accepting later U.S. entry. The court's reasoning can be summed up as "0 + 0 = 0": combining two lawful settlement agreements does not make the underlying conduct unlawful. The decision captures the core legal problem: holding many patents on a single product is not by itself proof of an antitrust violation, and valid patents generally allow their owners to exclude competitors for the life of each patent.
Those settlements also set the timing of what came next. Rather than risk patent-infringement liability by launching their products, the biosimilar companies settled with AbbVie on terms that let them enter the U.S. market at various points in 2023. In exchange, AbbVie agreed to stop enforcing its Humira patents against them, even though many of the patents ran until as late as 2034. Rejecting the alleged exchange of earlier European entry for delayed U.S. entry as an unlawful reverse payment, the court held that the deals were ordinary patent settlements rather than unlawful pay-for-delay agreements.
Competition arrived, but slowly
The court's ruling resolved the plaintiffs' antitrust claims, but not the broader policy debate. Humira biosimilars began entering the U.S. market in 2023, years after biosimilar competition had begun in Europe, and the FDA now lists multiple approved biosimilars to Humira's active ingredient, adalimumab.
Their arrival did not trigger an immediate, generic-style market shift. A 2024 study in JAMA Health Forum found that biosimilar adalimumab accounted for less than 2% of U.S. prescriptions by the fourth quarter of 2023. Even so, estimated net spending per adalimumab prescription fell sharply, by 43% between the fourth quarters of 2022 and 2023, suggesting that competition affected prices before biosimilars captured substantial volume.
Uptake later accelerated through contracting and distribution arrangements. IQVIA reported that Hyrimoz, an adalimumab biosimilar, reached 16% of U.S. adalimumab claims in June 2024 after a co-promotion arrangement with Cordavis, a CVS Caremark venture. These figures show that patent expiration is only one piece of the puzzle: formulary placement, rebates, interchangeability rules, and contracting all shape whether an approved competitor actually reaches patients.
What should the law regulate?
The Humira example points to a mismatch in the system. Patent law protects each patent individually, while competition policy asks what happens when those rights operate together.
Each side of the debate emphasizes one half of that mismatch. The Federal Trade Commission (FTC) has argued that dense portfolios can delay generic or biosimilar entry by forcing rivals to challenge numerous patents, even when some are ultimately invalidated. Critics of legislative limits, including the U.S. Chamber of Commerce, argue that labeling large portfolios as inherently abusive obscures the fact that separate patents may protect separate inventions and that broad restrictions could weaken incentives to improve medicines after approval.
Policymakers have several options for resolving the mismatch, each with trade-offs:
Patent cap. A biologic manufacturer could assert only a set number of patents against a biosimilar, although an arbitrary limit could disregard legitimate inventions.
Stronger USPTO scrutiny. Rather than imposing a numerical cap, the USPTO could make overlapping continuation patents harder to obtain, though stricter examination may be administratively difficult.
Loser pays. If a brand-name manufacturer asserts a patent and loses, it would bear more of the biosimilar maker's litigation costs, but fee shifting could deter enforcement of valid patents.
Greater FTC enforcement. Antitrust enforcement goes to the heart of anticompetitive conduct, but the Noerr-Pennington doctrine generally protects petitioning the government for patents, as the Humira litigation illustrates.
Do nothing. If patents were lawfully obtained, courts arguably should not punish companies for using them, yet inaction may leave economically rational patent accumulation standing as a barrier to entry.
From options to legislation
Several of these options already appear in pending legislation and regulatory efforts. The APPA (S. 1041) takes the patent-cap approach. As passed by the Senate, it targets patents such as those filed more than four years after a biologic's approval or claiming manufacturing methods the manufacturer does not use and generally allows a brand manufacturer to assert no more than 20 such listed patents, with an exemption for patents claiming therapeutic, diagnostic, or preventive uses and room for a court to raise the cap in the interests of justice or for good cause. The bill passed the Senate by unanimous consent on July 21, 2026, and was received in the House and "held at the desk" the same day, which means the House can take it up without first sending it to committee. As of October 10, 2026, the House had taken no further action.
The cap applies only when the biosimilar maker completes the patent-exchange process under the Biologics Price Competition and Innovation Act (“BPCIA”), commonly called the "patent dance." Because the Supreme Court held in Sandoz v. Amgen (2017) that the patent dance is optional, the cap would reach only biosimilar makers that complete the specified statutory steps.
A separate bipartisan proposal, the Eliminating Thickets to Increase Competition (“ETHIC”) Act, takes a different approach. It would allow only one patent per "patent group," meaning commonly owned patents linked through terminal disclaimers used to overcome obviousness-type double-patenting objections, to be asserted in infringement litigation. Unlike the APPA, it would reach both generic drugs and biosimilars. The House and Senate versions, H.R. 3269 and S. 2276, were introduced in 2025 and referred to the House and Senate Judiciary Committees, respectively; neither has advanced beyond committee. The House bill has nonetheless continued to add bipartisan cosponsors, most recently in April 2026.
Terminal disclaimers have also drawn regulators' attention, reflecting the "stronger USPTO scrutiny" option. In 2024, the FTC supported a proposed USPTO rule targeting terminal-disclaimer practices that can produce clusters of closely related patents. The USPTO withdrew the proposal in December 2024, citing resource constraints after receiving more than 300 comments.
Recent developments
In an October 7, 2026, analysis, the R Street Institute noted that the APPA has advanced furthest of the pending patent thicket bills and that both it and the ETHIC Act could come into play in the upcoming lame-duck session of Congress. The same analysis observed that the patents in Humira's portfolio were linked by 436 terminal disclaimers, underscoring why the ETHIC Act focuses on terminally disclaimed patent groups. It also identified related bipartisan measures pending in the 119th Congress, including the Medication Affordability and Patent Integrity Act (S. 2658), which has been reported out of committee and would require drug makers to give the USPTO the same patentability information they give the FDA.
Conclusion: Where should the line be drawn?
The patent-thicket debate is less about whether patents should exist than about how they should operate together. Humira remains the case policymakers return to because it captures both sides of that question: a portfolio that protected genuine improvements to a medicine also created a formidable barrier for would-be competitors. With Humira biosimilars now on the market and the APPA awaiting House action, the question is no longer what happened with Humira, but what rules should govern the next blockbuster biologic.