Dupixent (dupilumab) is one of the most commercially successful biologic drugs in the world, and several pharmaceutical companies are actively developing biosimilar versions of it. No dupilumab biosimilar has yet reached the market in the United States or Europe, but the groundwork is being laid across regulatory, manufacturing, and clinical fronts. For the millions of people who rely on Dupixent for conditions like atopic dermatitis, asthma, and chronic rhinosinusitis with nasal polyps, the arrival of biosimilars could reshape both access and cost.
What Dupixent Does and Why Copying It Is Complicated
Dupilumab is a monoclonal antibody that works by binding to part of the interleukin-4 receptor, specifically the IL-4Rα subunit. That binding blocks signaling from two inflammatory molecules, IL-4 and IL-13, which are central drivers of the type of immune overreaction known as type 2 inflammation.1PubMed Central. Dupilumab: Mechanism of action, clinical, and translational science This is the same pathway behind allergic responses, mucus overproduction, and the skin barrier breakdown seen in eczema. By targeting the shared receptor rather than a single cytokine, dupilumab covers a broader swath of type 2 inflammation than drugs that block just one molecule.
Dupilumab belongs to a class of antibodies called IgG4, and that matters for biosimilar development. Monoclonal antibodies are enormous, intricate molecules produced by living cells, and their structure includes a range of small chemical modifications that occur during and after manufacturing. These modifications can affect how the drug behaves in the body. Recent analytical work has revealed that IgG4 antibodies can carry unusual modifications that had not previously been described for this antibody class, including a rare type of sugar attachment (O-linked glycosylation) found in a region of the molecule involved in binding its target.2PubMed Central. Discovery and Characterization of Unusual O‐Linked Glycosylation of IgG4 Antibody Using LC‐MS For biosimilar developers, this means the reference product has to be characterized with extreme thoroughness. You cannot copy what you have not fully mapped, and IgG4 antibodies turn out to have more structural wrinkles than anyone expected.
Biosimilars Are Not Generics
If you have ever switched from a brand-name pill to a generic version, you might assume a biosimilar works the same way. It does not. A generic version of a small-molecule drug like ibuprofen is chemically identical to the original, atom for atom, and relatively simple to verify. A biosimilar is a biologic medicine made through a living cell system to be highly similar to an already-approved reference product, but because the manufacturing process involves living organisms, no two independently produced biologics will ever be absolutely identical at the molecular level. Minor differences in the sugar chains attached to the protein, in the folding patterns, or in trace impurities are expected and acceptable, as long as they do not change how the drug works clinically.
This is why the approval pathway for biosimilars is fundamentally different from the one used for generics. Rather than simply proving chemical sameness, a biosimilar developer has to build a case across multiple layers of evidence. The process starts with extensive analytical comparison showing the biosimilar’s structure and function closely match the original. It then moves into pharmacokinetic studies showing the drug behaves the same way in the body, and in some cases includes clinical trials comparing outcomes in patients. Regulators evaluate all of this together, using what is called a “totality of the evidence” approach.3PubMed Central. Biosimilars and the extrapolation of indications for inflammatory conditions
The Evolving Regulatory Bar
One of the more significant shifts happening in biosimilar regulation is a move toward streamlined development pathways. After more than two decades of clinical experience with approved biosimilars across many therapeutic areas, regulatory agencies have accumulated enough data to reconsider how much clinical testing is truly necessary. The emerging consensus is that if analytical comparison and pharmacokinetic studies demonstrate strong similarity, a full-scale comparative clinical trial may not always be required. The reasoning is straightforward: if the molecule looks the same, acts the same in lab assays, and reaches the same blood levels at the same rate, the chance that it will behave differently in patients is vanishingly small.4Bioanalysis. From analytical similarity to clinical confidence: how regulatory evolution ensures comparable immunogenicity in streamlined biosimilar development
This streamlined approach does not mean corners are being cut. Analytical characterization has become extraordinarily sophisticated, capable of detecting differences at a level that clinical trials cannot. The argument regulators are increasingly accepting is that well-designed pharmacokinetic studies, especially in healthy volunteers where there are fewer confounding factors from disease or other treatments, can provide sensitive and informative safety and immunogenicity data that align closely with what comparative clinical trials would show.5Bioanalysis. From analytical similarity to clinical confidence: how regulatory evolution ensures comparable immunogenicity in streamlined biosimilar development For dupilumab biosimilar developers, this evolution could shorten the path to approval, though the exact requirements will depend on what each regulatory agency demands for this particular molecule.
Extrapolation Across Indications
Dupixent is currently approved for a growing list of conditions: moderate-to-severe atopic dermatitis, certain types of asthma, chronic rhinosinusitis with nasal polyps, eosinophilic esophagitis, prurigo nodularis, and chronic obstructive pulmonary disease with a type 2 inflammatory profile. A biosimilar developer does not necessarily have to run separate clinical trials for every one of these indications. Regulatory agencies allow something called extrapolation, where clinical data generated in one condition can be used to support approval in others, provided the scientific justification is sound.
Extrapolation relies on the idea that if the biosimilar has been shown to match the reference product in its mechanism of action, its pharmacokinetics, and its clinical performance in one well-chosen indication, the same similarity should hold across other conditions driven by the same biological pathway.6PubMed Central. Biosimilars and the extrapolation of indications for inflammatory conditions For dupilumab, this is somewhat favorable because all of its approved uses involve the same underlying mechanism: blocking IL-4 and IL-13 through the IL-4Rα subunit. That shared mechanism makes it easier to argue that results in one indication should carry over. Still, extrapolation decisions are made case by case, and regulators may ask for additional data if they see meaningful differences in how the drug is used across conditions.
What Happens When Patients Switch
One of the most common concerns patients have about biosimilars is whether switching from the brand-name drug will cause problems. This is understandable: if you have spent months or years getting stable on Dupixent, the idea of changing to a different version feels risky. The clinical evidence on switching, drawn from biosimilars across many drug classes, is reassuring.
A systematic review and meta-analysis that pooled data from controlled studies found no statistically significant difference in safety between patients who switched from a reference biologic to a biosimilar and those who stayed on the original. Rates of serious adverse events, deaths, and treatment discontinuations were comparable between the two groups, and the incidence of anti-drug antibodies was similar as well.7PLOS ONE. Safety outcomes when switching between biosimilars and reference biologics: A systematic review and meta-analysis A separate systematic review reached the same conclusion, finding that the available switching data did not indicate major problems with efficacy, safety, or immune reactions when moving from the original to a biosimilar.8PubMed Central. The Efficacy, Safety, and Immunogenicity of Switching Between Reference Biopharmaceuticals and Biosimilars: A Systematic Review
These findings come from biosimilar classes with years of real-world switching experience, such as infliximab and adalimumab biosimilars. Dupilumab biosimilars specifically do not yet have switching data because they are not yet on the market. But the consistency of the switching evidence across other monoclonal antibodies provides a reasonable basis for expecting similar results.
The Nocebo Problem
One pattern that has emerged from switching studies deserves its own discussion. Some open-label and observational studies have reported higher discontinuation rates after patients switched to a biosimilar, but when researchers looked more closely, the increased dropouts were largely attributed to nocebo effects rather than genuine drug-related problems.9PubMed Central. The Efficacy, Safety, and Immunogenicity of Switching Between Reference Biopharmaceuticals and Biosimilars: A Systematic Review A nocebo effect is the opposite of a placebo effect: patients experience negative symptoms because they expect them, not because the treatment is actually causing harm.
This is not a trivial issue. How a switch is communicated to patients has a measurable impact on outcomes. Surveys of physicians and pharmacists have confirmed that the way a clinician frames the conversation about switching to a biosimilar can either mitigate or amplify the nocebo response.10Farmacia Hospitalaria. Knowledge, perceptions, attitude, barriers and facilitators of biosimilars use across specialty physicians and hospital pharmacists: A national survey If a doctor says, “We’re changing your medication because the hospital wants to save money,” the patient hears something very different from, “This is the same treatment with the same active ingredient, and all the clinical data show equivalent results.” The framing matters enormously. Patients who understand what a biosimilar is and why the switch is happening tend to do better than those who feel the decision was made without their input or for purely financial reasons.
For people currently on Dupixent who may eventually face a switch conversation, being aware that this psychological dynamic exists is genuinely useful. Feeling a vague sense that the new version “isn’t working as well” does not necessarily mean the drug has changed. It may mean your expectations have.
Interchangeability in the US Versus Europe
The regulatory framework around biosimilar switching differs between the US and the EU, and the distinction matters practically. In the European Union, regulators have taken the position that approved biosimilars are highly similar to and interchangeable with their reference products, and that additional dedicated switching studies are not required to support this conclusion.11PubMed Central. Safety, Immunogenicity and Interchangeability of Biosimilar Monoclonal Antibodies and Fusion Proteins: A Regulatory Perspective In practice, this means a physician in the EU can switch a patient from the reference product to an approved biosimilar with confidence that regulators consider the two functionally equivalent.
The United States has historically set a higher bar for what it calls “interchangeability,” which is a specific regulatory designation above and beyond basic biosimilar approval. To earn this label, a manufacturer must demonstrate that the biosimilar can be expected to produce the same clinical result as the reference product in any given patient, and that alternating or switching between the two carries no greater risk than using the original continuously.12PubMed Central. Interchangeability of Biosimilars: What Level of Clinical Evidence is Needed to Support the Interchangeability Designation in the United States? An interchangeable biosimilar in the US can be substituted at the pharmacy level without the prescriber’s intervention, similar to how generics work. A biosimilar without that designation requires the prescribing physician to authorize the switch.
The FDA has been evolving its thinking on this, and the practical gap between the US and EU approaches has been narrowing. But for dupilumab biosimilar developers targeting the US market, the interchangeability designation remains a meaningful competitive advantage worth pursuing, because it makes pharmacy-level substitution possible and removes a friction point in adoption.
What Biosimilars Could Do to Cost
Dupixent is expensive. In the US, the list price runs into tens of thousands of dollars per year, and even with insurance, copays can be substantial. The financial promise of biosimilars is one of the main reasons they attract so much attention from patients, payers, and health systems alike.
The pricing impact of biosimilars varies widely depending on how many competitors enter the market and how aggressively payers negotiate. Data from Singapore’s experience with biologic medicines illustrates the range. When the first infliximab biosimilar was listed there, it brought roughly a 57% price reduction. When a second biosimilar brand entered the market, prices dropped approximately 90% from the original reference product’s price.13PubMed Central. Impact of Value-Driven Healthcare Strategies for Biosimilar Adoption: The Singapore Story On average, biosimilars listed after multiple competitors were available saw around an 80% price reduction.14PubMed Central. Impact of Value-Driven Healthcare Strategies for Biosimilar Adoption: The Singapore Story These are not US numbers, and the American pharmaceutical market operates under very different pricing dynamics, but the direction is consistent across countries: more biosimilar competitors mean lower prices.
The US experience with adalimumab (Humira) biosimilars, which began entering the market in 2023, offers a more directly relevant preview. Price discounts have been more modest in the US than in some other markets, partly because of the complex rebate system that governs drug pricing. Still, even partial cost reduction on a drug as widely used as Dupixent would be meaningful. For patients who have struggled with affordability or who have been denied access because their insurer considered the drug too costly, biosimilar competition could expand the pool of people who can actually get treated.
Pediatric Considerations
Dupixent is approved for use in children as young as six months for atopic dermatitis, and pediatric use is an important part of its clinical profile. When biosimilars arrive, a natural question will be whether the data supporting them applies equally to children. The honest answer is that pediatric-specific biosimilar evidence remains limited across the board. A scoping review of biosimilar adoption in pediatrics found uncertainty surrounding safety and efficacy in children, driven by the lack of clinical trial data specifically conducted in younger populations.15Pharmaceut Med. Considerations for Biosimilar Adoption in Pediatrics: A Scoping Review
This does not mean biosimilars are unsafe for children. It means the evidence base is thinner than it is for adults, and the gap is being filled gradually through real-world experience, patient registries, and pharmacovigilance systems rather than dedicated pediatric clinical trials for each biosimilar. Regulators typically allow extrapolation from adult data to pediatric populations when the disease mechanism and drug behavior are expected to be similar, but parents and pediatricians understandably want more direct reassurance. For a drug like dupilumab that is heavily used in children with severe eczema, this gap will need attention as biosimilars approach the market. The review emphasized that building out pharmacovigilance and registry data will be important for validating extrapolation to pediatric indications and building provider confidence.16Pharmaceut Med. Considerations for Biosimilar Adoption in Pediatrics: A Scoping Review
The Manufacturing Puzzle for Dupilumab Specifically
Not all monoclonal antibodies are equally straightforward to copy, and dupilumab presents some particular challenges. As an IgG4 antibody, it belongs to a subclass that behaves differently from the more commonly biosimilar-ized IgG1 antibodies like adalimumab and infliximab. IgG4 antibodies undergo a natural process called Fab-arm exchange, where half of one antibody molecule can swap with half of another, creating hybrid molecules. This is a known feature of the subclass and is accounted for in the original drug’s design, but it adds a layer of complexity for biosimilar characterization.
On top of that, the discovery of unexpected post-translational modifications in IgG4 molecules, such as the O-linked glycosylation described earlier, means biosimilar developers cannot simply rely on established analytical playbooks developed for other antibody classes.17PubMed Central. Discovery and Characterization of Unusual O‐Linked Glycosylation of IgG4 Antibody Using LC‐MS They have to invest heavily in characterizing the reference product at an unusually granular level before they can begin to demonstrate that their own version matches. These challenges are solvable with modern analytical tools, but they explain why dupilumab biosimilar development timelines have not been as swift as some had expected.
The subcutaneous injection format of Dupixent also adds a device-related dimension. Biosimilar developers must not only match the molecule but also deliver it in a way that is comparable to the existing pre-filled syringe or autoinjector. Patients who self-inject at home have developed routines and expectations around the existing device, and a biosimilar with a dramatically different injection experience could affect adherence even if the drug inside is equivalent. Device design, injection volume, and needle gauge all factor into real-world adoption in ways that clinical pharmacology alone does not capture.
How Physicians and Pharmacists Feel About Biosimilars
The success of dupilumab biosimilars will depend not just on regulatory approval and pricing but on whether clinicians actually prescribe them. Surveys of specialty physicians and hospital pharmacists have found that while most recognize biosimilar switching as effective and safe, knowledge gaps and lingering hesitation persist.18Farmacia Hospitalaria. Knowledge, perceptions, attitude, barriers and facilitators of biosimilars use across specialty physicians and hospital pharmacists: A national survey Some prescribers remain uncertain about the nuances of biosimilar approval, extrapolation, and interchangeability. Others are comfortable with the science but worry about patient reactions, particularly the nocebo dynamic.
Dermatologists and allergists who prescribe Dupixent heavily may be among the later adopters if history with other biosimilar classes is any guide. Specialists in fields like rheumatology and gastroenterology, where biosimilars for infliximab and adalimumab have been available for years, have already been through the learning curve and are generally more comfortable with switching. The dermatology and allergy fields will be going through that transition for the first time with a major biologic, and the speed of uptake will depend heavily on how professional societies, payer policies, and early real-world data shape the conversation.