{"id":38808,"date":"2026-06-17T09:34:00","date_gmt":"2026-06-17T13:34:00","guid":{"rendered":"https:\/\/www.drugpatentwatch.com\/blog\/?p=38808"},"modified":"2026-05-10T12:46:21","modified_gmt":"2026-05-10T16:46:21","slug":"how-to-win-the-biosimilar-patent-dance-a-litigation-strategy-guide-for-biologics-and-biosimilar-applicants","status":"publish","type":"post","link":"https:\/\/www.drugpatentwatch.com\/blog\/how-to-win-the-biosimilar-patent-dance-a-litigation-strategy-guide-for-biologics-and-biosimilar-applicants\/","title":{"rendered":"How to Win the Biosimilar Patent Dance: A Litigation Strategy Guide for Biologics and Biosimilar Applicants"},"content":{"rendered":"\n
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Biologic drugs account for roughly 2% of all U.S. prescriptions. They generate 37% of total net drug spending [1]. That asymmetry is the commercial pressure behind every patent dispute in this industry, and it explains why the legal framework governing biosimilar entry \u2014 the Biologics Price Competition and Innovation Act (BPCIA) and its pre-litigation information exchange known as the ‘patent dance’ \u2014 attracts more strategic attention per case than almost any other area of pharmaceutical law.<\/p>\n\n\n\n

The biosimilar market stood at approximately $34 billion globally in 2024 and is projected to approach $97 billion by 2030 [2]. For a biosimilar developer who has spent $100 million to $250 million over seven to eight years building a product, getting the patent dance wrong can mean the difference between capturing that market and watching from the sidelines while a competitor who made better litigation choices launches first.<\/p>\n\n\n\n

This guide covers the patent dance in full \u2014 what it requires, what it does not require, where the real strategic leverage sits, and how the cases that have shaped this area of law should inform your decisions today. It draws on case law from Sandoz v. Amgen at the Supreme Court through the most recent Regeneron-Eylea multi-district litigation in the Northern District of West Virginia. It also references data from DrugPatentWatch, which tracks biologic patent portfolios, litigation filings, and expiration timelines in a format designed for competitive intelligence rather than academic study.<\/p>\n\n\n\n

What the BPCIA Actually Does<\/strong><\/h2>\n\n\n\n

Congress enacted the BPCIA as part of the Affordable Care Act in March 2010. It created an abbreviated approval pathway for follow-on biologics at the FDA, analogous to the pathway Hatch-Waxman established for small-molecule generics in 1984. A biosimilar applicant files an abbreviated Biologics License Application (aBLA) demonstrating that its product is ‘highly similar’ to an FDA-approved reference biologic with ‘no clinically meaningful differences’ in safety, purity, and potency [3].<\/p>\n\n\n\n

Because a biologic is manufactured in living cell systems and its molecular complexity makes exact replication impossible, this standard differs fundamentally from the bioequivalence test that governs small-molecule generics. That manufacturing complexity also means the intellectual property protecting a biologic can extend far beyond the core molecule. A single biologic may be covered by patents on its amino acid sequence, its cell line and fermentation process, its purification steps, its formulation, its device (auto-injector, prefilled syringe), its dosing regimen, and its approved indications. Patent thickets in this space are not rhetorical devices. They are real, deliberate, and sometimes contain more than a hundred distinct patents.<\/p>\n\n\n\n

The BPCIA attempted to manage this by creating a structured pre-litigation information exchange between the biosimilar applicant and the reference product sponsor (RPS). That exchange \u2014 the patent dance \u2014 has a defined sequence of steps, each tied to a statutory deadline. It culminates in two phases of potential patent litigation, with the first phase initiated during FDA review and the second triggered by the biosimilar’s notice of commercial marketing.<\/p>\n\n\n\n

The Mechanics: A Step-by-Step Breakdown of the Patent Dance<\/strong><\/h2>\n\n\n\n

Step 1: aBLA Submission and the Initial Disclosure<\/strong><\/h3>\n\n\n\n

The dance begins when the biosimilar applicant notifies the RPS within 20 days of the FDA accepting its aBLA for review. Under 42 U.S.C. \u00a7 262(l)(2)(A), the applicant must then provide a copy of its aBLA and detailed manufacturing information to the RPS. This is the most consequential single decision in the entire process. The applicant can choose to make this disclosure \u2014 and enter the dance \u2014 or it can withhold the information entirely.<\/p>\n\n\n\n

This is not a hypothetical choice. The Supreme Court confirmed in Sandoz Inc. v. Amgen Inc.<\/em> (2017) that the patent dance is not mandatory. An applicant who declines to provide its aBLA and manufacturing information faces a specific statutory consequence \u2014 the RPS may bring an immediate declaratory judgment action for artificial infringement \u2014 but the applicant cannot be compelled to produce the documents by injunction under federal law [4].<\/p>\n\n\n\n

The decision to participate or opt out is the first major strategic fork in the road.<\/p>\n\n\n\n

Step 2: The RPS Patent List \u2014 60 Days<\/strong><\/h3>\n\n\n\n

If the applicant enters the dance, the RPS has 60 days from receipt of the aBLA to provide its own list: all patents for which it believes a claim of infringement could reasonably be asserted against the biosimilar, along with patents it would be willing to license. This list is the heart of phase one litigation. The RPS faces a significant consequence for omission \u2014 under the BPCIA, the RPS generally forfeits its right to sue on patents that should have been included on this list but were not [5].<\/p>\n\n\n\n

That forfeiture provision creates a real incentive for the RPS to list broadly. A well-resourced originator with a large portfolio will list many patents, some of which are commercially important and some of which are tactical \u2014 included to consume the biosimilar applicant’s time and litigation budget during patent review.<\/p>\n\n\n\n

Step 3: The Applicant’s Response \u2014 60 Days<\/strong><\/h3>\n\n\n\n

Within 60 days of receiving the RPS patent list, the biosimilar applicant must provide a detailed statement for each listed patent explaining whether it is infringed and, if so, why the patent claims are invalid or unenforceable. If the applicant believes a patent is not infringed, it provides a detailed non-infringement position.<\/p>\n\n\n\n

This statement is a major undertaking. It requires claim charts, validity analysis, and infringement analysis for every listed patent. For a reference product with 30 or 40 listed patents, this is months of legal and technical work. For a reference product like Humira, against which AbbVie built a portfolio of over 130 patents, the exercise borders on the impractical.<\/p>\n\n\n\n

Step 4: The RPS Reply and Narrowing \u2014 60 Days<\/strong><\/h3>\n\n\n\n

The RPS has 60 days to reply with its own patent-by-patent counter-positions. After this exchange, the parties negotiate to identify a subset of patents to litigate in phase one. The biosimilar applicant may agree to litigate up to the number of patents the RPS specifies, and the RPS agrees not to seek a preliminary injunction on any patents outside that agreed list during phase one.<\/p>\n\n\n\n

If the parties cannot agree on a list within 15 days of the RPS reply, the statute provides a default: the biosimilar applicant selects one patent to litigate immediately, and the RPS may add patents up to a number equal to the applicant’s selection. Both parties then bring their full claims on those patents within 30 days.<\/p>\n\n\n\n

Step 5: Phase One Litigation<\/strong><\/h3>\n\n\n\n

Phase one litigation is filed once the parties have identified the patents to litigate. If the dance proceeds by the book, phase one litigation is typically filed roughly 245 days after FDA acceptance of the aBLA [6]. In Amgen v. Hospira \u2014 a textbook example cited by the Center for Biosimilars \u2014 phase one litigation was filed 201 days after acceptance.<\/p>\n\n\n\n

Phase one runs concurrently with FDA review of the aBLA. This is the design intent: resolve the most commercially significant patent disputes before the biosimilar is actually ready to launch.<\/p>\n\n\n\n

Step 6: The 180-Day Notice and Phase Two<\/strong><\/h3>\n\n\n\n

No later than 180 days before commercial launch, the biosimilar applicant must give the RPS written notice of its intent to market. This notice triggers the right to phase two patent litigation \u2014 on any patents not addressed in phase one \u2014 and starts a 180-day window during which the parties can seek injunctive relief.<\/p>\n\n\n\n

The Supreme Court’s decision in Sandoz<\/em> also resolved a major ambiguity about this notice: an applicant can give the 180-day notice before FDA approval, not just after. This matters considerably. An applicant who gives early notice \u2014 even before the FDA has finished its review \u2014 can potentially launch the day approval comes through, rather than waiting six months post-approval [4]. That optionality is one of the patent dance’s most powerful levers for biosimilar applicants.<\/p>\n\n\n\n

Phase two litigation can cover any patent the RPS did not include in phase one, any patent that issued after the aBLA was filed, and any patent on which the applicant changes its non-infringement or invalidity position.<\/p>\n\n\n\n

The Opt-Out Decision: Strategic Arguments on Both Sides<\/strong><\/h2>\n\n\n\n

Since Sandoz<\/em> confirmed that the dance is optional, biosimilar applicants have continued to weigh participation carefully. The practical reality, documented by Finnegan in their analysis of post-Sandoz<\/em> case filings, is that compliance with the patent dance has actually increased slightly since 2017, despite widespread predictions that applicants would exploit the ruling to opt out en masse [7].<\/p>\n\n\n\n

Why do most applicants still participate? The answer is mostly defensive.<\/p>\n\n\n\n

The Case for Participating<\/strong><\/h3>\n\n\n\n

When an applicant enters the dance, it gains control over which patents enter phase one litigation. The applicant chooses how many patents to litigate and can strategically limit phase one to patents it believes are weak \u2014 patents it can defeat quickly, clearing legal space for launch. That control disappears entirely if the applicant opts out.<\/p>\n\n\n\n

An applicant who opts out cedes litigation timing to the RPS. The RPS can immediately file a declaratory judgment action covering its entire patent portfolio \u2014 potentially 50, 80, or 130 patents \u2014 in a single consolidated action. That is an enormous litigation burden to absorb at once, particularly for a smaller biosimilar developer with limited resources [7].<\/p>\n\n\n\n

Participating in the dance also reduces the risk of an injunction. Courts have shown more willingness to issue preliminary injunctions in cases where the biosimilar applicant appears to have evaded the statutory process. The RPS narrative \u2014 ‘they refused to tell us how they made the product, and now they want to launch anyway’ \u2014 has real persuasive force before some judges.<\/p>\n\n\n\n

The Case for Opting Out<\/strong><\/h3>\n\n\n\n

The strongest argument for opting out is speed. A biosimilar applicant who withholds its aBLA and manufacturing information avoids the multi-month disclosure and negotiation sequence. If the reference product’s patent portfolio is known to be weak \u2014 perhaps because the core patents have already expired or been invalidated in other proceedings \u2014 opting out and filing early notice of commercial marketing can compress the pre-launch litigation timeline substantially.<\/p>\n\n\n\n

Sandoz used this logic in the original Zarxio case. Sandoz’s counsel argued that since Amgen’s own public filings indicated it did not believe it had material patents on Neupogen (the reference product, which already had 24 years of exclusivity), there was no commercial reason to engage the full dance process [8].<\/p>\n\n\n\n

Opting out also prevents the RPS from receiving a detailed roadmap of the biosimilar’s manufacturing process and non-infringement positions before litigation begins. That disclosure \u2014 while protected by statutory confidentiality provisions \u2014 is still sensitive information that the RPS can use in litigation preparation.<\/p>\n\n\n\n

AbbVie and Humira: The Definitive Patent Thicket Case Study<\/strong><\/h2>\n\n\n\n

No case study illustrates BPCIA strategy at its extreme better than Humira (adalimumab). AbbVie obtained initial FDA approval for Humira in 2002. The original composition-of-matter patent \u2014 the ‘382 patent \u2014 expired in 2016. By that point, AbbVie had filed for and obtained 132 additional patents covering Humira’s formulation, manufacturing process, dosing, and delivery systems, with expiration dates extending well past 2016 and, on some patents, to 2034 [9].<\/p>\n\n\n\n

Approximately 90% of those additional patents were issued in 2014 or later \u2014 years after Humira was already a blockbuster generating tens of billions in annual revenue [9]. Critics, including Alvotech in its own litigation filings, argued that many of those patents covered inventions AbbVie did not actually use to manufacture Humira, and that the patent estate was designed specifically to overwhelm competitors with litigation rather than to protect genuine innovation.<\/p>\n\n\n\n

The result: every major biosimilar developer that attempted to challenge the Humira portfolio ultimately settled rather than fight. AbbVie granted European market entry licenses in 2018 in exchange for commitments to delay U.S. launches until 2023 \u2014 five years after European competition began and seven years after the original core patent expired [10]. Each settlement also included royalty commitments on future U.S. sales, meaning AbbVie would continue generating revenue from Humira even after biosimilar entry.<\/p>\n\n\n\n

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‘Without settlements, biosimilar manufacturers simply could not have navigated the 136-patent estate owned by AbbVie and ‘batted one thousand.’ Numerous similar examples exist for other biologics.’ \u2014 Association for Accessible Medicines [11]<\/p>\n<\/blockquote>\n\n\n\n

For reference product sponsors, the Humira playbook demonstrated the effectiveness of building a large, multi-layered patent estate before patent cliffs arrive. For biosimilar developers, it illustrated the asymmetric litigation burden created by patent thickets: even a developer with genuinely strong invalidity arguments faces an existential financial risk when those arguments must be tested across 130 patents simultaneously.<\/p>\n\n\n\n

Courts have not found the patent thicket strategy itself to be an antitrust violation. In the antitrust case brought by indirect Humira purchasers, the U.S. District Court for the Northern District of Illinois dismissed claims that AbbVie’s patent accumulation violated Section 2 of the Sherman Act, finding that obtaining patents \u2014 even patents of questionable quality \u2014 is not inherently monopolization [12]. The individual settlement agreements were also found not to have crossed the anticompetitive threshold established by the Supreme Court in FTC v. Actavis (2013), at least on the facts as litigated in that case.<\/p>\n\n\n\n

That ruling is significant for current strategy. It confirms that patent thickets are a legally permissible \u2014 if commercially aggressive \u2014 tool for reference product sponsors, and that biosimilar developers must address them through the patent dance, through PTAB challenges, or through settlement negotiations rather than antitrust litigation.<\/p>\n\n\n\n

The Regeneron-Eylea Litigation: A Modern BPCIA Case Study<\/strong><\/h2>\n\n\n\n

The current Eylea (aflibercept) biosimilar litigation offers a more recent and in some ways more instructive case study than Humira, because it shows the full multi-defendant BPCIA process playing out in real time under the rules that now govern the field.<\/p>\n\n\n\n

Regeneron’s regulatory exclusivity for Eylea expired on May 18, 2024. In the preceding months, Regeneron filed BPCIA suits against at least six separate biosimilar developers: Amgen, Mylan\/Biocon, Celltrion, Formycon, Samsung Bioepis, and Sandoz. The cases were consolidated as a multi-district litigation in the Northern District of West Virginia, presided over by Chief Judge Thomas Kleeh [13].<\/p>\n\n\n\n

Regeneron asserted dozens of patents across multiple cases. In its second complaint against Celltrion alone \u2014 filed in May 2024 \u2014 Regeneron listed 25 patents covering method-of-treatment claims, formulation claims, composition-of-matter claims, manufacturing claims, device claims, and packaging claims [14].<\/p>\n\n\n\n

The Preliminary Injunction Battles<\/strong><\/h3>\n\n\n\n

The Eylea litigation produced one of the most closely watched preliminary injunction sequences in recent BPCIA history. With regulatory exclusivity expiring May 18, 2024, and FDA approval of the first biosimilars following two days later, Regeneron moved for temporary restraining orders against multiple defendants in the MDL on May 17, 2024 \u2014 the day before exclusivity expired [15].<\/p>\n\n\n\n

The outcomes diverged sharply across defendants. On June 24, 2024, the district court granted Regeneron’s motion for a preliminary injunction against Samsung Bioepis and Formycon on U.S. Patent No. 11,084,865 \u2014 a formulation patent. The Federal Circuit affirmed those injunctions on January 29, 2025, rejecting the biosimilar developers’ arguments that they had raised a ‘substantial question’ of invalidity of the ‘865 patent [16].<\/p>\n\n\n\n

Against Amgen, the court reached the opposite conclusion. On September 23, 2024, the district court denied Regeneron’s preliminary injunction motion, finding that Amgen did not infringe the ‘865 patent [17]. Amgen launched its Eylea biosimilar Pavblu (aflibercept-ayyh) at risk in October 2024 and reported $700 million in Pavblu sales for 2025.<\/p>\n\n\n\n

The divergence in outcomes across defendants \u2014 preliminary injunctions against Samsung and Formycon, denial against Amgen \u2014 illustrates how biosimilar-specific manufacturing and formulation choices can determine litigation outcomes on the same patent. Amgen’s process for Pavblu apparently put it outside the claims of the ‘865 patent in a way that Samsung’s process for Opuviz did not.<\/p>\n\n\n\n

Settlements Resolve Most Defendants<\/strong><\/h3>\n\n\n\n

By early 2026, Regeneron had settled with all but one defendant. Mylan\/Biocon settled in April 2025. Sandoz and Formycon settled in September 2025. Celltrion settled in October 2025. Samsung Bioepis settled in February 2026, obtaining a license to launch Opuviz in the U.S. from January 2027 [18]. The preliminary injunction against Samsung was vacated as part of the settlement.<\/p>\n\n\n\n

Amgen, which launched at risk in October 2024 and held the denial of Regeneron’s preliminary injunction in its favor, remains in litigation as of this writing. That ongoing dispute is the clearest current example of an at-risk launch strategy in the BPCIA context \u2014 a topic covered in detail below.<\/p>\n\n\n\n

Professionals tracking these proceedings can use DrugPatentWatch to monitor the patent numbers being asserted in active BPCIA litigations, cross-reference expiration dates, and identify which claims have been challenged at the PTAB \u2014 giving legal and business teams a consolidated picture of the patent landscape before they commit to litigation strategy.<\/p>\n\n\n\n

PTAB as a Strategic Weapon: Inter Partes Review in Biologics Litigation<\/strong><\/h2>\n\n\n\n

The Patent Trial and Appeal Board (PTAB) is a specialized administrative tribunal within the USPTO that hears challenges to the validity of granted patents. It operates on a shorter timeline than district court litigation (12-18 months from petition to final written decision), applies a lower standard of proof for challengers (preponderance of the evidence rather than clear and convincing evidence), and allows broader claim construction in some contexts than district courts.<\/p>\n\n\n\n

For biosimilar developers, PTAB proceedings \u2014 primarily Inter Partes Review (IPR) and Post-Grant Review (PGR) \u2014 are a distinct strategic track from the BPCIA patent dance. They run in parallel with district court litigation and can be filed at any time, subject to statutory timing limits for PGR.<\/p>\n\n\n\n

The Numbers Make the Case<\/strong><\/h3>\n\n\n\n

The data on PTAB outcomes in biologic patent cases is striking. In Fiscal Year 2024, biologic and pharmaceutical patent petitions constituted only 6% of total PTAB petitions \u2014 but achieved an institution rate of 73%, higher than the overall IPR institution rate of 68% [19]. When biologic patents reached a final written decision, approximately 68% were found ‘all unpatentable’ and only about 16% were found ‘all patentable’ [19].<\/p>\n\n\n\n

The cumulative average cancellation rate of instituted claims across all AIA proceedings stands at approximately 74%, with biologic-specific IPRs yielding roughly 75% of decisions holding at least one reviewed claim unpatentable [19]. Federal Circuit affirmance of PTAB decisions has hovered consistently between 70% and 80% since 2015 [19].<\/p>\n\n\n\n

Celltrion deployed this strategy aggressively in the Eylea litigation, filing multiple IPR petitions against Regeneron’s formulation patents simultaneously with district court defense. By the time Celltrion settled, four previous IPR petitions had already been decided against Regeneron’s Eylea patents, with PTAB finding claims unpatentable [20].<\/p>\n\n\n\n

IPR vs. PGR: Choosing the Right Forum<\/strong><\/h3>\n\n\n\n

IPR is available for any patent and can be filed at any time (subject to the one-year bar from service of a complaint). It is limited to grounds of anticipation and obviousness over prior art consisting of patents and printed publications.<\/p>\n\n\n\n

PGR is available only for patents with an effective filing date of March 16, 2013 or later (post-AIA patents), and must be filed within nine months of grant. It allows any ground of invalidity, including Section 112 written description and enablement arguments \u2014 which are particularly relevant for biologic patents, where the functional breadth of antibody claims has repeatedly been challenged under written description requirements.<\/p>\n\n\n\n

The nine-month window for PGR is the crucial constraint. A biosimilar developer who identifies a newly granted biologic patent \u2014 particularly one covering a formulation or method claim that will affect its product \u2014 should evaluate PGR eligibility immediately upon grant, not months later when the nine-month window may have closed.<\/p>\n\n\n\n

In 2025, PTAB underwent institutional reforms under Director Squires that significantly reduced IPR institution rates. IPR filings declined to 60.4% of total PTAB petitions in 2025, down from 73% in 2024, while procedural denials surged [21]. This shift has prompted some practitioners to evaluate ex parte reexamination as an alternative \u2014 the USPTO grants approximately 95% of reexam requests, though the claim cancellation rate is lower at around 14% [21].<\/p>\n\n\n\n

Timing and Synchronization<\/strong><\/h3>\n\n\n\n

The strategic value of PTAB proceedings in the BPCIA context depends on timing. An IPR filed too late \u2014 after a district court has already ruled on the same validity question \u2014 may face a parallel estoppel issue. An IPR filed too early may not align its schedule with the district court’s claim construction order or summary judgment briefing, reducing its leverage on preliminary injunction proceedings.<\/p>\n\n\n\n

The optimal approach is to file IPR petitions on the highest-priority patents in the RPS’s portfolio at or shortly after entering the patent dance \u2014 before phase one litigation is filed \u2014 so that PTAB institution decisions are available during the critical preliminary injunction window in district court. An institution decision at the PTAB, finding that the patent merits review, creates at minimum an argument that the patentee cannot demonstrate the strong likelihood of success on the merits required for a preliminary injunction.<\/p>\n\n\n\n

At-Risk Launch: The Most Aggressive Biosimilar Strategy<\/strong><\/h2>\n\n\n\n

An at-risk launch \u2014 commercially marketing a biosimilar while patent litigation remains pending and unresolved \u2014 is the highest-risk, highest-reward strategy available to a biosimilar developer. It requires the biosimilar to have received FDA approval, to have served the 180-day notice of commercial marketing, and for the 180-day period to have elapsed. If no court has entered an injunction barring launch, the applicant can sell product into the market.<\/p>\n\n\n\n

The exposure is significant. If the biosimilar applicant loses the patent case after launch, it faces potential damages measured by the RPS’s lost profits and\/or a reasonable royalty on all units sold during the at-risk period. For a successful biosimilar product, those damages can run to billions of dollars.<\/p>\n\n\n\n

The strategic calculation depends on several factors:<\/p>\n\n\n\n

    \n
  • Strength of the invalidity or non-infringement position on the asserted patents<\/li>\n\n\n\n
  • Whether the court has denied a preliminary injunction \u2014 a denial means the court found the patentee has not established likelihood of success on the merits or that the balance of hardships does not favor an injunction<\/li>\n\n\n\n
  • The commercial value of early market entry \u2014 in a crowded biosimilar market, being first can be worth hundreds of millions in revenue from patients and payers who lock in formulary coverage in the early months<\/li>\n\n\n\n
  • The RPS’s historical litigation behavior \u2014 does it pursue damages aggressively in at-risk situations, or does it shift to settlement negotiations once launch occurs?<\/li>\n<\/ul>\n\n\n\n

    Amgen’s launch of Pavblu in October 2024, following the district court’s denial of Regeneron’s preliminary injunction, is the most recent major example of this approach succeeding commercially in the short term. Amgen had a specific basis for confidence: the court had found on the specific facts that Amgen’s process did not infringe the asserted formulation patent. That denial is not a guarantee of ultimate success on validity \u2014 Regeneron appealed \u2014 but it gave Amgen a credible legal foundation for the at-risk decision.<\/p>\n\n\n\n

    Contrast this with the Samsung and Formycon situation in the same litigation, where the court entered preliminary injunctions. Both companies were blocked from launch and ultimately settled for licensed entry dates roughly three years post-approval. The difference in legal outcome between Amgen and Samsung \u2014 on essentially the same patent, in the same MDL \u2014 came down to product-specific technical choices made years earlier in manufacturing development.<\/p>\n\n\n\n

    The 180-Day Notice: Optionality and Weaponization<\/strong><\/h2>\n\n\n\n

    The 180-day notice of commercial marketing is one of the most underappreciated tactical instruments in the BPCIA toolkit. The Supreme Court confirmed in Sandoz<\/em> that this notice can be provided before FDA approval \u2014 not just after \u2014 meaning an applicant who files early notice can theoretically compress the pre-launch window to zero: serve notice upon aBLA filing, receive FDA approval 180 days or more later, and launch the day approval comes through.<\/p>\n\n\n\n

    This changes the timeline math entirely. An RPS that relies on the 180-day notice to anchor its phase two litigation schedule can find itself with less time to seek injunctive relief than it anticipated, particularly if FDA review moves faster than expected or if the applicant’s notice was filed early in the review period.<\/p>\n\n\n\n

    For biosimilar applicants, giving early notice has a cost: it starts the clock on phase two litigation before FDA approval is certain. If approval is delayed or denied, the notice period can expire before launch occurs, requiring the applicant to provide new notice. The 180-day window is also the period during which preliminary injunction motions are most commonly filed and decided \u2014 the applicant who gave early notice is effectively inviting the RPS to bring its injunction motion sooner rather than later.<\/p>\n\n\n\n

    The strategic use of early notice is most clearly justified when the applicant has high confidence in FDA approval timing \u2014 for example, when the aBLA is in a late stage of review with no significant outstanding issues \u2014 and when the applicant’s non-infringement or invalidity positions are strong enough to withstand a preliminary injunction motion.<\/p>\n\n\n\n

    Phase Two Patents: The Continuing Exposure Problem<\/strong><\/h2>\n\n\n\n

    A design flaw \u2014 or feature, depending on your perspective \u2014 of the BPCIA is that phase two patent litigation has essentially no ceiling on the number of patents the RPS can assert. Phase two covers any patent the RPS did not include in phase one, any patent that issued after the aBLA was filed, and any patent on which the applicant changes its position. For a reference product with an active patent prosecution program, new patents can keep issuing throughout the aBLA review period and beyond, continuously expanding the RPS’s phase two arsenal.<\/p>\n\n\n\n

    AbbVie exploited this structure deliberately with Humira. By filing continuation applications throughout the product lifecycle, AbbVie kept new patents issuing years after biosimilar developers had completed their phase one patent analyses. Each new patent was technically available for phase two assertion, even if it covered the same general technology as previously litigated claims.<\/p>\n\n\n\n

    Biosimilar developers should monitor the prosecution status of the RPS’s active patent families using tools like DrugPatentWatch throughout the litigation period, not just at the time of aBLA filing. Identifying continuation applications that are likely to issue within the relevant timeframe \u2014 and evaluating whether pre-issuance PGR filings are available \u2014 can reduce the phase two exposure before it materializes.<\/p>\n\n\n\n

    Keytruda: The Next Patent Dance Battleground<\/strong><\/h2>\n\n\n\n

    The next major BPCIA confrontation is taking shape around Keytruda (pembrolizumab), Merck’s immune checkpoint inhibitor and the world’s top-selling drug, with 2024 revenues of $25.5 billion. The main Keytruda composition-of-matter patent expires in 2028. At least 14 companies are in late-stage biosimilar development, and Merck has reportedly filed over 237 related patents to defend the franchise [22].<\/p>\n\n\n\n

    Pembrolizumab PTAB activity was notable in 2024. Merck itself filed IPR petitions against nine patents held by Johns Hopkins University covering methods of treating microsatellite instability-high cancers with pembrolizumab \u2014 a pre-emptive strike against patents that, if upheld, could have required Merck to license from a third party [23]. This illustrates that the BPCIA patent dance and PTAB proceedings are not tools used exclusively by biosimilar developers. An RPS can use PTAB challenges to clear patents held by others that threaten its own reference product’s commercial position.<\/p>\n\n\n\n

    For biosimilar developers targeting pembrolizumab, the strategic challenge is significant. Merck’s patent estate for Keytruda is broad and actively maintained. Biosimilar applicants will need detailed patent intelligence \u2014 mapping each Merck patent family to the specific processes and formulations they plan to use \u2014 to build non-infringement positions and identify credible invalidity arguments before entering the patent dance.<\/p>\n\n\n\n

    Interchangeability: The Regulatory Designation That Changes Market Dynamics<\/strong><\/h2>\n\n\n\n

    The BPCIA creates two tiers of biosimilar approval: ‘biosimilar’ and ‘interchangeable.’ A product designated as interchangeable can be substituted for the reference biologic by a pharmacist without prescriber intervention \u2014 the equivalent of automatic substitution that applies to small-molecule generics at the pharmacy counter. An ordinary biosimilar requires prescriber or practice authorization for substitution in most states.<\/p>\n\n\n\n

    Interchangeability designation has traditionally required an additional clinical study (a ‘switching study’) demonstrating that alternating between the biosimilar and the reference product produces no additional risk compared to continued use of the reference product. The FDA proposed in October 2025 to streamline interchangeability requirements, potentially eliminating the switching study requirement for most products [24]. If finalized, that change could substantially reduce development costs and timelines for interchangeable designation \u2014 which currently gives the first interchangeable biosimilar for a given molecule a one-year period of exclusivity against other interchangeable biosimilars (though not against ordinary biosimilars).<\/p>\n\n\n\n

    From a litigation strategy perspective, interchangeability creates an additional patent exposure: the BPCIA permits a second round of patent proceedings specifically for interchangeable designation. If a biosimilar applicant subsequently seeks interchangeable status, that filing can restart certain dance elements for patents covering the additional data or formulation changes required for the designation. This is a relatively uncommon but real source of secondary litigation exposure.<\/p>\n\n\n\n

    Settlement Strategy: Structured Negotiation in Complex Multi-Patent Cases<\/strong><\/h2>\n\n\n\n

    Every major BPCIA litigation that has concluded \u2014 Humira, Stelara (ustekinumab), and now most of the Eylea cases \u2014 has ended in settlement rather than a final merits ruling. This pattern is not coincidence. It reflects the structure of the litigation itself.<\/p>\n\n\n\n

    Neither party has an obvious interest in a full trial on 30 or 40 patents. The RPS wants to maximize exclusivity period without incurring the cost and uncertainty of trying a large patent portfolio, some of which may be vulnerable. The biosimilar applicant wants market access as quickly as possible \u2014 and a licensed entry date, even if it means a royalty or a delayed launch, is often more valuable than a protracted litigation with an uncertain outcome.<\/p>\n\n\n\n

    BPCIA settlements typically include the following terms:<\/p>\n\n\n\n

      \n
    • A defined license commencement date \u2014 the date the biosimilar applicant can begin selling in the U.S. market<\/li>\n\n\n\n
    • A royalty rate on U.S. net sales, often tiered by volume<\/li>\n\n\n\n
    • A release of all patent claims related to the biosimilar product<\/li>\n\n\n\n
    • A covenant not to launch before the commencement date (violation of which triggers the full litigation exposure again)<\/li>\n<\/ul>\n\n\n\n

      The Samsung Bioepis-Regeneron settlement is a recent template. Samsung received a licensed launch date of January 2027 for Opuviz \u2014 roughly 32 months after FDA approval in May 2024. Amgen, having launched at risk in October 2024, avoided that delay entirely but carries ongoing litigation risk that Samsung no longer faces.<\/p>\n\n\n\n

      Settlement Timing and Leverage<\/strong><\/h3>\n\n\n\n

      The biosimilar applicant’s negotiating leverage is highest before phase two litigation begins in earnest. Once phase two is filed and the court has set a trial schedule, both parties are accumulating litigation costs and are committed to specific arguments. Pre-phase-two settlement discussions, initiated after a favorable phase one result or after successful PTAB institution decisions, tend to produce the most favorable terms for applicants.<\/p>\n\n\n\n

      The RPS’s leverage peaks around the preliminary injunction phase. A preliminary injunction blocks launch, eliminates near-term commercial pressure on the RPS, and removes the biosimilar applicant’s ability to negotiate against an at-risk launch position. Amgen’s ability to resist RPS pressure in the Eylea case \u2014 and its reported $700 million in 2025 Pavblu sales \u2014 directly traces to the court’s denial of the preliminary injunction, which removed the injunction as a settlement tool from Regeneron’s arsenal.<\/p>\n\n\n\n

      Settlement leverage for biosimilar applicants also improves significantly when multiple applicants are litigating the same reference product simultaneously. In an MDL with six defendants, the RPS faces the prospect of trying six separate cases \u2014 or reaching six separate settlements. The first settlement sets a market price for the license. Subsequent applicants can use that benchmark in their own negotiations, while the RPS faces increasing difficulty justifying better terms for later settlers (which would create most-favored-nation issues under some settlement agreements).<\/p>\n\n\n\n

      DrugPatentWatch and the Intelligence Layer<\/strong><\/h2>\n\n\n\n

      Strategy in BPCIA litigation depends on patent intelligence. You need to know which patents cover the reference product, when they expire, whether any have been challenged at the PTAB, what the claim scope is, and how similar claims have fared in other proceedings. You need to track continuation applications that have not yet issued. You need to monitor the RPS’s prosecution activity for signs of new filings that might generate phase two exposure.<\/p>\n\n\n\n

      DrugPatentWatch aggregates this data into a searchable, competitive intelligence format designed for legal and business teams, not academic researchers. For a biosimilar applicant beginning aBLA preparation, systematically mapping the reference product’s patent estate using DrugPatentWatch \u2014 identifying expiration dates, prosecution history, prior PTAB challenges, and claim scope \u2014 is the first step in building the non-infringement and invalidity positions required for the dance. For an RPS preparing to receive an aBLA notification, the same tool helps assess the breadth of the patent portfolio and identify which patents warrant inclusion in the phase one list.<\/p>\n\n\n\n

      Jurisdictional Considerations: Where These Cases Are Filed<\/strong><\/h2>\n\n\n\n

      BPCIA cases can be filed in any federal district court, subject to personal jurisdiction over the defendants. In practice, a small number of districts have developed institutional familiarity with BPCIA litigation: Delaware, the Northern District of California, and \u2014 increasingly \u2014 the Northern District of West Virginia, where the Eylea MDL was consolidated and which has become a significant venue for multi-defendant BPCIA proceedings under Chief Judge Kleeh.<\/p>\n\n\n\n

      The Federal Circuit handles virtually all appeals from BPCIA patent decisions, creating a unified appellate body. Federal Circuit precedent on claim construction, preliminary injunction standards, and jurisdiction in BPCIA cases applies uniformly regardless of the district court where the case originates.<\/p>\n\n\n\n

      Jurisdiction in BPCIA cases presents specific issues not present in other patent litigation. Biosimilar developers, particularly those organized outside the U.S., have challenged personal jurisdiction on the ground that filing an aBLA and providing notice of commercial marketing \u2014 activities that occur through FDA submissions, not necessarily through physical presence in a district \u2014 do not create sufficient minimum contacts with any particular state. The Federal Circuit has ruled on this directly in the Eylea cases: filing an aBLA, serving notice of commercial marketing, and establishing a nationwide distribution channel are sufficient to establish minimum contacts [16]. That ruling significantly limits the viability of personal jurisdiction defenses in future BPCIA cases filed against foreign biosimilar developers.<\/p>\n\n\n\n

      Legislative Developments: The Affordable Prescriptions for Patients Act<\/strong><\/h2>\n\n\n\n

      Congress has taken notice of the patent thicket problem. Senators John Cornyn and Richard Blumenthal introduced the Affordable Prescriptions for Patients Act of 2023, which passed the Senate in July 2024 [25]. The bill would cap the number of patents a reference product sponsor can assert against a biosimilar applicant at 20, with specific rules governing how additional patents can be added to that initial list.<\/p>\n\n\n\n

      If enacted into law, the cap would fundamentally change the math of the patent thicket strategy. An RPS with 130 patents could no longer deploy all of them in litigation; it would be forced to select its 20 strongest claims, which the biosimilar applicant’s legal team can then analyze and attack with far greater concentration. The economic leverage of the thicket \u2014 the practical impossibility of defending against 130 patents simultaneously \u2014 disappears when the number is capped at 20.<\/p>\n\n\n\n

      As of this writing, the bill has not been enacted. The House has not taken it up. But its passage through the Senate signals a directional policy intent that biosimilar and originator companies should factor into long-range planning. Reference product sponsors building patent estates for biologics approved today should not assume that a 130-patent litigation strategy will remain legally available in five or ten years.<\/p>\n\n\n\n

      Practical Guidance for Biosimilar Applicants: A Pre-aBLA Checklist<\/strong><\/h2>\n\n\n\n

      The decisions that determine BPCIA litigation outcomes are mostly made before the aBLA is filed \u2014 in product design, manufacturing process development, and early patent analysis. By the time the dance begins, much of the strategic flexibility is already constrained by technical choices made in the lab.<\/p>\n\n\n\n

      Map the Reference Product’s Patent Estate Early<\/strong><\/h3>\n\n\n\n

      At least 18-24 months before aBLA filing, conduct a comprehensive freedom-to-operate (FTO) analysis of the reference product’s patent portfolio. Use DrugPatentWatch and the USPTO’s Patent Center to identify all active patent families, continuation applications, and pending applications that could generate new patents before or during aBLA review. Flag patents in each category: manufacturing process, formulation, device\/delivery, dosing\/method of treatment, and composition of matter.<\/p>\n\n\n\n

      Design Around the Strongest Patents<\/strong><\/h3>\n\n\n\n

      Where feasible, design your manufacturing process and formulation to fall outside the claims of the reference product’s highest-value patents. A biosimilar that does not infringe the RPS’s key formulation or process patents does not need to win the invalidity argument \u2014 it simply needs to demonstrate non-infringement, which is a lower burden and produces a cleaner litigation narrative. Amgen’s ability to argue non-infringement of Regeneron’s ‘865 patent in the Eylea MDL, while Samsung and Formycon could not, almost certainly reflects manufacturing choices made years before the aBLA was filed.<\/p>\n\n\n\n

      Build Your PTAB Challenge List<\/strong><\/h3>\n\n\n\n

      Identify the RPS patents most likely to be asserted in phase one, and evaluate them for IPR eligibility. For recently granted patents \u2014 those within nine months of grant \u2014 evaluate PGR eligibility with priority. File PTAB petitions early enough that institution decisions arrive before the preliminary injunction briefing schedule in district court.<\/p>\n\n\n\n

      Decide on Dance Participation Before You File<\/strong><\/h3>\n\n\n\n

      The opt-in or opt-out decision should be made as part of overall launch strategy, not reactively after receiving the RPS’s first communication. Factors include: the breadth of the RPS’s patent portfolio, the strength of your invalidity and non-infringement positions, your capacity to absorb a large-scale declaratory judgment action if you opt out, and the commercial value of controlling the phase one patent selection.<\/p>\n\n\n\n

      Practical Guidance for Reference Product Sponsors: Building a Defensible Portfolio<\/strong><\/h2>\n\n\n\n

      The RPS’s strategic position in the patent dance depends almost entirely on decisions made during the product development and patent prosecution phases \u2014 years or decades before any biosimilar aBLA is filed.<\/p>\n\n\n\n

      Diversify Patent Coverage Across Multiple Layers<\/strong><\/h3>\n\n\n\n

      A robust biologic patent estate covers the molecule itself (where possible), the manufacturing process (cell line, fermentation, purification), the formulation, the delivery device, and the clinically validated dosing methods. Originator companies that rely exclusively on composition-of-matter patents face a patent cliff when the core patent expires. Those with layered coverage across multiple patent families can continue generating non-infringement positions on later-issued patents after the core patent falls.<\/p>\n\n\n\n

      Maintain Active Prosecution Programs<\/strong><\/h3>\n\n\n\n

      Continuation applications are a legitimate tool for maintaining prosecution activity on inventions that were covered by a pending application. They extend the period during which new claims can be issued and create the potential for phase two patent assertions against aBLA filers. The legislative headwinds \u2014 particularly the pending Affordable Prescriptions for Patients Act \u2014 may eventually limit this strategy, but for portfolios being built today, continuation filing programs remain a standard component of biologic IP strategy.<\/p>\n\n\n\n

      Use the Phase One List Strategically<\/strong><\/h3>\n\n\n\n

      The RPS’s phase one list should not simply include every patent the legal team thinks might survive challenge. A bloated phase one list is expensive to litigate, dilutes judicial attention, and signals that the RPS is using the list as a litigation burden strategy rather than a genuine patent enforcement tool \u2014 a narrative that some judges have found persuasive in preliminary injunction proceedings. Selecting a focused list of high-confidence patents for phase one, while reserving continuation-based patents for phase two, often produces better outcomes than comprehensive assertion from the start.<\/p>\n\n\n\n

      Model the Settlement Decision Before Phase Two<\/strong><\/h3>\n\n\n\n

      After phase one results are known \u2014 whether through a final decision or a series of claim construction rulings \u2014 the RPS should quantitatively model the expected value of continuing to trial versus settling for a defined royalty stream. RPS counsel often focuses on the legal merits of the remaining patents; business teams should run parallel analysis on the commercial value of different settlement structures versus the risk-adjusted value of continued litigation.<\/p>\n\n\n\n

      The Science-IP Interface: Why the Manufacturing Process Is Always in Play<\/strong><\/h2>\n\n\n\n

      One of the BPCIA’s most consequential features \u2014 and one that distinguishes it from Hatch-Waxman fundamentally \u2014 is the central role of manufacturing information in the litigation. When a biosimilar applicant provides its aBLA and manufacturing information to the RPS at Step 1 of the dance, it is disclosing precisely how it makes the product. That information directly shapes the RPS’s patent list, because many of the most commercially important biologic patents cover process steps, cell culture conditions, purification sequences, and formulation choices \u2014 not the final molecule.<\/p>\n\n\n\n

      This creates an asymmetry that runs throughout the litigation. The RPS, upon receiving the aBLA, knows exactly which of its process patents may be infringed. The biosimilar applicant, in drafting its non-infringement positions, must disclose its technical positions on those process claims before trial. The discovery generated by the dance is broader and more technically intensive than anything produced in comparable Hatch-Waxman litigation.<\/p>\n\n\n\n

      It also means that the RPS’s ‘right’ to know how the biosimilar is made \u2014 enforced through the dance structure and confirmed by the Sandoz<\/em> decision’s consequence rule \u2014 is a genuine competitive advantage. A biosimilar applicant that opts out of the dance does so partly to protect its manufacturing trade secrets, accepting the litigation consequences in exchange for confidentiality.<\/p>\n\n\n\n

      What International Experience Teaches<\/strong><\/h2>\n\n\n\n

      Europe has no equivalent of the patent dance. The European Medicines Agency (EMA) evaluates biosimilar applications through a scientific review process, and patent disputes are handled entirely through national court systems under each member state’s law, without the structured pre-litigation exchange the BPCIA creates.<\/p>\n\n\n\n

      The result: Humira biosimilars launched in Europe in October 2018 \u2014 five years before they launched in the United States. The differential is almost entirely attributable to the scale and success of AbbVie’s U.S. patent strategy versus the more fragmented patent landscape across European jurisdictions, where the identical products faced narrower, more easily invalidated patent claims in most national courts.<\/p>\n\n\n\n

      Canada’s Patented Medicines (Notice of Compliance) (PM(NOC)) Regulations create a different structure \u2014 one where the originator must list patents it considers relevant to the reference product, and biosimilar developers can either challenge those patents or accept a 24-month stay of approval. The Canadian framework has generally produced shorter delays than the U.S. BPCIA, though recent litigation shows that complex formulation patents can generate significant disputes even under PM(NOC). The JAMP v. AbbVie decision in 2024, where a Canadian federal court declined to grant an injunction against JAMP’s adalimumab biosimilar Simlandi despite finding infringement of one AbbVie patent, illustrates that Canadian courts weigh public interest considerations \u2014 including patient access \u2014 more explicitly in the injunction analysis than U.S. courts typically do [26].<\/p>\n\n\n\n

      What the Amgen-Pavblu at-Risk Launch Means for Future Strategy<\/strong><\/h2>\n\n\n\n

      Amgen’s at-risk launch of Pavblu in October 2024 \u2014 following a court’s denial of a preliminary injunction \u2014 and its subsequent $700 million in reported 2025 sales will function as a reference point for future biosimilar strategy decisions. It demonstrates concretely that the at-risk launch strategy, when supported by a genuine non-infringement position and a favorable preliminary injunction ruling, can be commercially transformative.<\/p>\n\n\n\n

      Future biosimilar applicants facing multi-defendant BPCIA proceedings where one defendant has already achieved a preliminary injunction denial \u2014 on a patent also being asserted against them \u2014 will study Amgen’s technical basis for that denial carefully. The ‘865 Regeneron patent, which covers a specific formulation characteristic, could not be successfully asserted against Amgen’s process. The other defendants did not achieve the same result. The lesson is not that at-risk launches are universally viable, but that product-specific technical choices, made in manufacturing development, can be the decisive factor in whether an at-risk launch is defensible.<\/p>\n\n\n\n

      Key Takeaways<\/strong><\/h2>\n\n\n\n
        \n
      • The BPCIA patent dance is optional, not mandatory. Biosimilar applicants can opt out entirely, though doing so surrenders control over which patents enter phase one litigation and invites the RPS to bring a comprehensive declaratory judgment action covering its full portfolio.<\/li>\n\n\n\n
      • The most consequential strategic decisions in BPCIA litigation are made years before aBLA filing \u2014 in manufacturing process design, patent FTO analysis, and early identification of PTAB challenge candidates.<\/li>\n\n\n\n
      • PTAB proceedings (IPR and PGR) are a high-efficacy parallel forum for challenging biologic patents. Biologic patent petitions at the PTAB achieve a 73% institution rate and approximately 75% of final written decisions find at least one claim unpatentable. These proceedings should be integrated into BPCIA litigation strategy, not treated as a separate option.<\/li>\n\n\n\n
      • The AbbVie-Humira patent thicket strategy \u2014 130+ patents, mass settlement at 2023 entry dates, royalties on post-entry sales \u2014 remains the defining example of originator IP strategy at its most aggressive. Courts have declined to treat it as an antitrust violation. Congress is considering legislation to cap assertable patents at 20. Reference product sponsors should model both scenarios in long-range planning.<\/li>\n\n\n\n
      • The Regeneron-Eylea MDL illustrates how the same patent can produce opposite outcomes against different defendants, based entirely on product-specific manufacturing and formulation choices. Amgen’s denial of a preliminary injunction, and its subsequent at-risk launch and $700 million in 2025 Pavblu sales, reflect decisions made in manufacturing development, not in the courtroom.<\/li>\n\n\n\n
      • Early notice of commercial marketing \u2014 provided before FDA approval \u2014 can enable launch the day approval arrives, without an additional 180-day wait. This optionality is most valuable when approval timing is highly predictable and invalidity or non-infringement positions are strong.<\/li>\n\n\n\n
      • The 180-day notice of commercial marketing remains the trigger for phase two litigation. Phase two has no effective ceiling on the number of patents the RPS can assert. Monitoring the RPS’s active prosecution program throughout the litigation period is essential to managing phase two exposure.<\/li>\n\n\n\n
      • Settlement is the most common outcome in BPCIA litigation. Leverage for biosimilar applicants peaks before phase two litigation is underway, after favorable PTAB institution decisions, or when the court has denied a preliminary injunction. Modeled expected value \u2014 comparing defined license terms against risk-adjusted trial outcomes \u2014 should drive settlement timing decisions.<\/li>\n<\/ul>\n\n\n\n
        \n\n\n\n

        Frequently Asked Questions<\/strong><\/h2>\n\n\n\n

        1. If the patent dance is optional under Sandoz v. Amgen, why do most biosimilar applicants still participate?<\/strong><\/h3>\n\n\n\n

        The main reason is control. When a biosimilar applicant participates in the dance, it determines which patents enter phase one litigation \u2014 it can select patents it believes are weakest, limiting phase one to manageable scope. An applicant that opts out cedes that control entirely; the RPS may file a declaratory judgment action asserting its entire patent portfolio at once, which can run to dozens or hundreds of patents in cases involving heavily patented biologics. The litigation burden of a full-portfolio declaratory judgment action is often more costly and uncertain than the structured disclosure process the dance requires, even accounting for the manufacturing information that must be disclosed. Post-Sandoz<\/em> data compiled by Finnegan shows that patent dance participation actually increased slightly in the years following the 2017 decision.<\/p>\n\n\n\n

        2. What is the difference between a Phase One and Phase Two patent in BPCIA litigation, and why does it matter strategically?<\/strong><\/h3>\n\n\n\n

        Phase one patents are those identified through the dance’s negotiation process as patents to litigate during FDA review of the aBLA. Both parties agree on which patents to litigate in phase one, and the RPS cannot seek a preliminary injunction on patents outside that agreed list during the phase one period. Phase two patents are everything else \u2014 patents the RPS did not list in phase one, patents that issued after aBLA filing, and patents on which the applicant changes its position. Phase two litigation is triggered by the biosimilar’s 180-day notice of commercial marketing and effectively has no cap on the number of patents the RPS can assert. This means a large-portfolio RPS can hold significant patent firepower in reserve for phase two, creating exposure for the biosimilar applicant even after it has won on every phase one patent.<\/p>\n\n\n\n

        3. How does the interchangeability designation affect BPCIA litigation exposure?<\/strong><\/h3>\n\n\n\n

        Interchangeable designation allows pharmacists to substitute the biosimilar for the reference product without prescriber intervention \u2014 the same automatic substitution that applies to small-molecule generics. Commercially, it can significantly increase formulary access and prescription volume. Legally, seeking interchangeable designation after initial approval can restart elements of the patent dance for patents covering the additional data or formulation changes required for that designation. The first product to achieve interchangeable status for a given reference biologic also receives a period of exclusivity against other interchangeable biosimilars (though not against ordinary biosimilars). FDA proposed in 2025 to streamline interchangeability requirements by potentially eliminating the switching study requirement, which could reduce the incremental cost and timeline of seeking the designation substantially if finalized.<\/p>\n\n\n\n

        4. Can a reference product sponsor use PTAB proceedings, or are those a tool only for biosimilar developers?<\/strong><\/h3>\n\n\n\n

        Any party can file PTAB petitions against any patent. Reference product sponsors use IPR and PGR to challenge patents held by third parties \u2014 including academic institutions and non-practicing entities \u2014 that might affect the RPS’s own freedom to operate on its reference product. Merck’s 2023-2024 IPR filings against Johns Hopkins University patents covering pembrolizumab treatment methods are a direct example. From a biosimilar developer’s perspective, the fact that an RPS may challenge third-party patents on its own reference product’s technology \u2014 and thereby establish a public record of invalidity arguments \u2014 can be useful intelligence when the biosimilar developer is evaluating its own PTAB strategy against the RPS’s portfolio.<\/p>\n\n\n\n

        5. What should a biosimilar applicant do if it identifies a new continuation patent issued by the RPS after the aBLA has been filed?<\/strong><\/h3>\n\n\n\n

        Act immediately on two fronts. First, evaluate whether the new patent is eligible for PGR \u2014 patents granted to post-AIA applications can be challenged on any ground of invalidity within nine months of grant. PGR eligibility closes permanently when that window passes, and the broader invalidity grounds available in PGR (including Section 112 written description and enablement) are not available in IPR. Second, assess whether the new patent should have been included on the RPS’s phase one patent list \u2014 if it was strategically withheld from the list despite covering the biosimilar, the RPS may face a forfeiture argument in phase two. Tools like DrugPatentWatch can be configured to provide alerts on new patent issuances from specific assignees, giving legal teams real-time notice when new continuation patents issue from the RPS’s active patent families.<\/p>\n\n\n\n

        \n\n\n\n

        References<\/strong><\/h2>\n\n\n\n
          \n
        1. Grand View Research. (2024). Biologics market size, share & growth analysis report, 2030.<\/em> Grand View Research. https:\/\/www.grandviewresearch.com\/industry-analysis\/biologics-market<\/li>\n\n\n\n
        2. Mordor Intelligence. (2025). Biosimilars market size, trends, growth & share analysis 2025\u20132030.<\/em> Mordor Intelligence. https:\/\/www.mordorintelligence.com\/industry-reports\/global-biosimilars-market-industry<\/li>\n\n\n\n
        3. Biologics Price Competition and Innovation Act of 2009, Pub. L. No. 111-148, 42 U.S.C. \u00a7 262 (2010).<\/li>\n\n\n\n
        4. Sandoz Inc. v. Amgen Inc.<\/em>, 137 S. Ct. 1664 (2017).<\/li>\n\n\n\n
        5. Congressional Research Service. (2025, June). Pharmaceutical patent disputes: Biosimilar entry under the Biologics Price Competition and Innovation Act (BPCIA)<\/em> [IF13029]. Library of Congress. https:\/\/www.congress.gov\/crs-product\/IF13029<\/li>\n\n\n\n
        6. Center for Biosimilars. (2021, July 24). The inner workings of the BPCIA patent dance.<\/em> https:\/\/www.centerforbiosimilars.com\/view\/the-inner-workings-of-the-bpcia-patent-dance<\/li>\n\n\n\n
        7. Finnegan, Henderson, Farabow, Garrett & Dunner, LLP. (2020, May). Following the patent dance three years after Sandoz.<\/em> Bloomberg Law. https:\/\/news.bloomberglaw.com\/ip-law\/insight-following-the-patent-dance-three-years-after-sandoz<\/li>\n\n\n\n
        8. Center for Biosimilars. (2017). US Supreme Court to consider Sandoz vs Amgen biosimilar patent dance case on April 26.<\/em> https:\/\/www.centerforbiosimilars.com\/view\/us-supreme-court-to-consider-sandoz-vs-amgen-biosimilar-patent-dance-case-on-april-26<\/li>\n\n\n\n
        9. Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. (2020, June 18). AbbVie’s enforcement of its ‘patent thicket’ for Humira under antitrust scrutiny.<\/em> https:\/\/www.mintz.com\/insights-center\/viewpoints\/2231\/2020-06-18-abbvies-enforcement-its-patent-thicket-humira-under<\/li>\n\n\n\n
        10. DrugPatentWatch. (2025, November). The thicket maze: A strategic guide to navigating and dismantling drug patent fortresses.<\/em> https:\/\/www.drugpatentwatch.com\/blog\/the-thicket-maze-a-strategic-guide-to-navigating-and-dismantling-drug-patent-fortresses\/<\/li>\n\n\n\n
        11. Association for Accessible Medicines. (2025, June). Patent settlements are necessary to help combat patent thickets.<\/em> https:\/\/accessiblemeds.org\/resources\/blog\/patent-settlements-are-necessary-to-help-combat-patent-thickets\/<\/li>\n\n\n\n
        12. AJMC. (2024). Humira: The first $20 billion drug.<\/em> https:\/\/www.ajmc.com\/view\/humira-the-first-20-billion-drug<\/li>\n\n\n\n
        13. Goodwin Procter LLP. (2024, June). Updates on aflibercept biosimilar approvals and BPCIA litigation.<\/em> Big Molecule Watch. https:\/\/www.bigmoleculewatch.com\/2024\/06\/07\/updates-on-aflibercept-biosimilar-approvals-and-bpcia-litigation\/<\/li>\n\n\n\n
        14. Venable LLP \/ BiologicsHQ. (2024, May). Regeneron files second BPCIA complaint against Celltrion’s proposed EYLEA biosimilar CT-P42.<\/em> https:\/\/biologicshq.com\/regeneron-files-second-bpcia-complaint-against-celltrions-proposed-eylea-biosimilar-ct-p42\/<\/li>\n\n\n\n
        15. Big Molecule Watch. (2024, January). Updates on aflibercept BPCIA litigation.<\/em> https:\/\/www.bigmoleculewatch.com\/2024\/01\/05\/updates-on-aflibercept-bpcia-litigation\/<\/li>\n\n\n\n
        16. Big Molecule Watch. (2025, March). Federal Circuit affirms injunction against Celltrion in aflibercept BPCIA litigation.<\/em> https:\/\/www.bigmoleculewatch.com\/2025\/03\/06\/federal-circuit-affirms-injunction-against-celltrion-in-aflibercept-bpcia-litigation\/<\/li>\n\n\n\n
        17. Big Molecule Watch. (2024). BPCIA litigations.<\/em> https:\/\/www.bigmoleculewatch.com\/bpcia-patent-litigations\/<\/li>\n\n\n\n
        18. Venable LLP \/ BiologicsHQ. (2026, February). Regeneron and Samsung Bioepis settle EYLEA BPCIA litigations related to Opuviz.<\/em> https:\/\/biologicshq.com\/regeneron-and-samsung-bioepis-settle-eylea-bpcia-litigations-related-to-opuviz\/<\/li>\n\n\n\n
        19. PTAB Law Blog. (2025, January). Trial statistics trends at the PTAB: 2024 edition.<\/em> https:\/\/www.ptablaw.com\/2025\/01\/06\/trial-statistics-trends-at-the-ptab-2024-edition\/<\/li>\n\n\n\n
        20. Sterne, Kessler, Goldstein & Fox. (2023). Biologics at the PTAB: Statistics and insights into notable biologics decisions.<\/em> https:\/\/www.sternekessler.com\/news-insights\/insights\/biologics-ptab-statistics-and-insights-notable-biologics-decisions\/<\/li>\n\n\n\n
        21. Rothwell Figg \/ Biosimilars IP. (2025\u20132026). Biosimilars law bulletin.<\/em> https:\/\/www.biosimilarsip.com\/<\/li>\n\n\n\n
        22. ChinaPathology.org. (2025, December). Future biosimilars: Upcoming patent expirations and market entry.<\/em> https:\/\/chinapathology.org\/future-biosimilars-upcoming-patent-expirations-and-market-entry<\/li>\n\n\n\n
        23. Fish & Richardson. (2025, February). Biologics and biosimilars landscape 2024: IP, policy, and market developments.<\/em> https:\/\/www.fr.com\/insights\/thought-leadership\/blogs\/biologics-and-biosimilars-landscape-2024-ip-policy-and-market-developments\/<\/li>\n\n\n\n
        24. Rothwell Figg \/ Biosimilars IP. (2025, October). FDA moves to accelerate biosimilar approvals.<\/em> https:\/\/www.biosimilarsip.com\/<\/li>\n\n\n\n
        25. Center for Biosimilars. (2024). Breaking down biosimilar barriers: The patent system.<\/em> https:\/\/www.centerforbiosimilars.com\/view\/breaking-down-biosimilar-barriers-the-patent-system<\/li>\n\n\n\n
        26. Gowling WLG. (2024, January). Federal Court clarifies validity and evidence-related legal principles, and declines to grant injunction for infringed patent in HUMIRA decision.<\/em> https:\/\/gowlingwlg.com\/en\/insights-resources\/articles\/2024\/federal-court-clarifies-humira-decision<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

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