Last updated: September 1, 2026
Sarilumab, marketed as Kevzara by Sanofi and Regeneron, is an interleukin-6 receptor antagonist approved for rheumatoid arthritis and polymyalgia rheumatica in the United States. Its commercial profile has improved as Sanofi expanded the product beyond rheumatoid arthritis, but Kevzara remains a secondary asset within Sanofi’s immunology portfolio, well behind Dupixent. The principal medium-term risk is not immediate small-molecule generic entry. It is biosimilar competition after the U.S. biologic exclusivity period and the expiry of relevant formulation, manufacturing, and use patents.
What is sarilumab and how is Kevzara positioned commercially?
Sarilumab is a fully human monoclonal antibody that binds the interleukin-6 receptor and inhibits IL-6-mediated signaling. Sanofi and Regeneron developed the drug under a global collaboration.
Kevzara is marketed in prefilled syringes and pens at a 150 mg or 200 mg dose administered subcutaneously every two weeks. The drug is used with methotrexate or other conventional disease-modifying antirheumatic drugs, or as monotherapy when those treatments are unsuitable.
The main commercial indications are:
| Market |
Indication |
Regulatory milestone |
| United States |
Moderate-to-severe rheumatoid arthritis |
FDA approval, May 2017 |
| European Union |
Moderate-to-severe rheumatoid arthritis |
European approval, 2017 |
| United States |
Polymyalgia rheumatica in adults with inadequate response to corticosteroids or corticosteroid tapering |
FDA approval, 2023 |
| Other markets |
Rheumatoid arthritis and related inflammatory diseases |
Country-specific approvals |
The U.S. polymyalgia rheumatica approval broadened the addressable market. It also gave Sanofi a differentiated growth route because the disease is common in older adults and often requires prolonged corticosteroid therapy. The indication does not eliminate competition from conventional immunosuppressants or other biologics, but it increases Kevzara’s use beyond the crowded rheumatoid arthritis market. [1]
How large are Kevzara sales and what is the financial trajectory?
Sanofi’s public reporting indicates that Kevzara annual sales have reached approximately €1 billion and continued to grow into 2024. The product has moved from a specialty rheumatoid arthritis asset toward a broader immunology franchise product, supported by increased use in polymyalgia rheumatica and international expansion.
Estimated reported sales trajectory
| Year |
Approximate Sanofi-reported sales |
Principal commercial driver |
| 2021 |
Approximately €0.7 billion |
Rheumatoid arthritis demand and broader biologic use |
| 2022 |
Approximately €0.9 billion |
Continued market penetration |
| 2023 |
Approximately €1.1 billion |
Growth before and around the U.S. polymyalgia rheumatica launch |
| 2024 |
Approximately €1.2 billion |
Expanded indication, volume growth, and international sales |
The figures represent Sanofi’s reported net sales and should not be treated as worldwide gross sales or product-level operating profit. Sanofi does not generally disclose Kevzara’s standalone margin, regional profitability, or detailed royalty economics in the same level of detail as total company results. Regeneron records economics under its collaboration arrangements rather than reporting a separate global product P&L equivalent to Sanofi’s disclosure. [2][3]
Kevzara’s revenue quality is relatively strong because biologic rheumatoid arthritis treatment is chronic and prescription persistence can be high. The product remains exposed to payer controls, step therapy, biosimilar substitution, and competition from IL-6 inhibitors, TNF inhibitors, JAK inhibitors, and other targeted therapies.
Its financial trajectory depends on four variables:
- Growth in polymyalgia rheumatica.
- Continued share retention in rheumatoid arthritis.
- Net price after rebates and government discounts.
- Timing and depth of biosimilar entry.
Kevzara is commercially important to Sanofi but does not have the concentration risk of a company whose revenue depends on one product. Dupixent is the dominant Sanofi immunology asset, while Kevzara provides a smaller, established revenue stream with additional lifecycle opportunities.
When does sarilumab lose U.S. biologic exclusivity?
Kevzara received its first U.S. biologics license approval on May 22, 2017. Under the Biologics Price Competition and Innovation Act, a reference product generally receives 12 years of reference-product exclusivity from first licensure. On that statutory basis, the core U.S. biologic exclusivity period runs to approximately May 2029. [4]
This date does not necessarily determine the first commercial biosimilar launch. Patent litigation, settlement agreements, manufacturing patents, pediatric exclusivity, injunctions, and regulatory review timing can move the effective launch date.
U.S. exclusivity timeline
| Event |
Date or period |
| FDA approval of Kevzara |
May 22, 2017 |
| Four-year biosimilar application filing restriction |
Approximately May 22, 2021 |
| Twelve-year reference-product exclusivity |
Approximately May 22, 2029 |
| Earliest practical biosimilar launch |
Dependent on patent resolution and FDA approval |
A biosimilar applicant may have been able to file a U.S. application after the four-year restriction, but FDA approval cannot take effect until the statutory exclusivity period expires. The applicant must also navigate the BPCIA patent-exchange process, commonly called the patent dance, unless it elects a different litigation strategy.
What patents protect sarilumab and Kevzara?
Sarilumab protection is likely divided among several patent categories rather than a single blocking patent:
- Antibody composition and sequence patents.
- Antigen-binding and receptor-binding claims.
- Pharmaceutical composition claims.
- Stable liquid formulation claims.
- Dosing and administration claims.
- Manufacturing and cell-culture process claims.
- Method-of-use claims for rheumatoid arthritis and polymyalgia rheumatica.
Sanofi and Regeneron are the relevant commercial parties, although ownership and licensing may vary by patent family and jurisdiction. The drug is a biologic, so the U.S. patent framework differs from that of a conventional tablet. Kevzara does not have a standard small-molecule Orange Book patent listing structure. FDA biologics are tracked through the Purple Book, while patent disputes proceed under the BPCIA and ordinary patent law. [5]
The most commercially relevant patents are those that could delay or increase the cost of biosimilar launch. Composition patents generally carry the greatest blocking value. Once core antibody claims expire, formulation, dosing, and manufacturing patents may still create litigation leverage, but they are less likely to prevent all biosimilar competition if an applicant can design around them.
A complete patent-by-patent expiration analysis requires review of U.S., European, and other national patent registers, including patent-term adjustments, supplementary protection certificates, terminal disclaimers, continuations, divisionals, and litigation outcomes. Public FDA approval records alone do not establish the complete international patent estate.
What is the Orange Book and Purple Book status of Kevzara?
Kevzara is regulated as a biologic under a BLA, not as an NDA-approved small molecule. The relevant FDA reference is the Purple Book, which identifies licensed biological products and biosimilar or interchangeable relationships. The Orange Book is primarily relevant to drug products approved under the Federal Food, Drug, and Cosmetic Act.
Consequences for market entry include:
- No conventional ANDA pathway for sarilumab.
- No automatic Orange Book patent certification under Paragraph IV.
- Biosimilar applicants must use the 351(k) pathway.
- Patent disputes generally arise under the BPCIA.
- Interchangeability requires a separate FDA determination and may affect pharmacy substitution.
Kevzara does not fit the standard generic-entry model used for oral medicines such as tablets or capsules. A biosimilar applicant must demonstrate high similarity and no clinically meaningful differences from the reference product, supported by analytical, pharmacokinetic, immunogenicity, and, where required, clinical evidence. [4][6]
Which companies are challenging sarilumab exclusivity?
No major sarilumab biosimilar challenger had publicly established a U.S. commercial presence as of the latest broadly available regulatory and company disclosures. The absence of a marketed biosimilar does not mean that the product is free from future challenge. Large biologics manufacturers and specialist biosimilar companies could enter once the commercial value justifies development and litigation costs.
Potential challenger groups include:
- Sandoz.
- Amgen.
- Biocon Biologics.
- Celltrion.
- Samsung Bioepis.
- Fresenius Kabi.
- Organon.
- Pfizer.
- Teva.
These companies have existing biosimilar platforms, but there is no basis to attribute a specific sarilumab filing or litigation action to each company without a public regulatory or court record.
What is the Paragraph IV challenge risk for sarilumab?
Paragraph IV certification is not the principal U.S. pathway for Kevzara because the product is a biologic. A biosimilar applicant would generally use the 351(k) pathway rather than submit an ANDA with a Paragraph IV certification.
The practical equivalent of a Paragraph IV challenge is a BPCIA patent dispute involving:
- Patent-listing disclosure and exchange.
- Infringement claims by the reference-product sponsor.
- Declaratory judgment actions.
- Preliminary injunction requests.
- Settlement agreements governing the launch date.
- Patent challenges in the Federal Circuit or district courts.
The commercial risk is therefore better described as biosimilar litigation risk rather than Paragraph IV risk.
What formulation patents protect Kevzara?
Kevzara is supplied as a ready-to-use liquid biologic in a prefilled syringe or pen. Formulation protection may cover excipient combinations, pH ranges, protein concentration, aggregation control, storage stability, and container-closure systems.
Formulation patents can matter because a biosimilar must match the reference product closely enough to support regulatory approval while avoiding valid claims. The commercial value of these patents depends on claim scope and whether the biosimilar can use a different buffer system, concentration, device, or manufacturing sequence.
Device patents can also affect the prefilled pen or syringe presentation. Device claims may delay a particular presentation without blocking a biosimilar supplied in a vial or alternative injector.
How strong is the sarilumab patent estate?
Kevzara’s patent estate is likely moderate rather than exceptionally strong from a long-term exclusivity perspective.
Strengths
- The drug has biologic complexity that makes substitution more difficult than generic tablet entry.
- Core antibody and manufacturing claims can create substantial development and litigation costs.
- The 12-year U.S. biologic exclusivity period extends protection beyond the earliest composition-patent expiration in some cases.
- Formulation and device patents can complicate biosimilar commercialization.
Weaknesses
- Sarilumab was first approved in 2017, so the product is approaching the period when biosimilar developers can prepare commercial launches.
- A biologic does not receive permanent protection from manufacturing and formulation claims.
- Rheumatoid arthritis has multiple competing mechanisms and established treatment algorithms.
- A biosimilar can enter with a different device or formulation if it satisfies FDA requirements.
- Patent settlements may permit entry before every asserted patent expires.
The strongest protection is likely the combination of regulatory exclusivity, antibody composition claims, and manufacturing know-how. The weakest protection is likely to be narrow method-of-use or device claims that can be designed around.
What patent litigation affects sarilumab?
There was no widely reported, market-defining U.S. sarilumab biosimilar litigation comparable to the major litigation histories involving adalimumab, ustekinumab, or ranibizumab in the public record available through the latest reporting period.
That litigation profile can change rapidly after a biosimilar applicant provides notice under the BPCIA. The relevant litigation questions will include:
- Whether Sanofi or Regeneron asserts composition patents.
- Whether manufacturing information is available for discovery.
- Whether the biosimilar applicant seeks a declaratory judgment.
- Whether the parties agree to a licensed launch date.
- Whether a settlement includes restrictions on formulation, indication, or device presentation.
How does Kevzara compare with competing IL-6 drugs?
Kevzara competes mainly with Roche’s Actemra, whose active ingredient is tocilizumab. Actemra has earlier market entry, broader historical positioning, intravenous and subcutaneous formulations, and established use in several inflammatory diseases. Kevzara competes through subcutaneous delivery, a two-week dosing schedule, and expansion into polymyalgia rheumatica.
| Attribute |
Kevzara |
Actemra |
| Active ingredient |
Sarilumab |
Tocilizumab |
| Mechanism |
IL-6 receptor antagonist |
IL-6 receptor antagonist |
| Sponsor |
Sanofi and Regeneron |
Roche/Genentech |
| U.S. first approval |
2017 |
2010 |
| Main established use |
Rheumatoid arthritis; polymyalgia rheumatica |
Rheumatoid arthritis and several additional indications |
| Delivery |
Subcutaneous syringe and pen |
Intravenous and subcutaneous presentations |
| Competitive issue |
Later entry and narrower indication history |
Earlier entry, broader indication base, and larger clinical footprint |
Actemra’s earlier approval creates a different patent and biosimilar timetable. Kevzara can benefit if physicians prefer its dosing and delivery profile, but it lacks Actemra’s breadth of indications and longer market history.
What generic entry risks exist for sarilumab?
Sarilumab faces low conventional generic risk and meaningful biosimilar risk.
Near-term risk
Near-term erosion is likely to come from payer negotiations, formulary competition, and price concessions rather than biosimilar substitution. Rheumatoid arthritis treatment is highly competitive, and payers can shift patients among TNF inhibitors, JAK inhibitors, IL-6 inhibitors, and other biologics.
Medium-term risk
The primary risk begins around the end of U.S. biologic exclusivity in 2029. A first biosimilar could produce:
- Lower net prices.
- Greater payer use of step edits.
- Reduced physician loyalty.
- Lower refill persistence where substitution is permitted.
- Higher rebate requirements from Sanofi.
- Pressure on international prices before U.S. entry.
A single biosimilar may have a limited initial effect if interchangeability is absent. Multiple entrants would create materially greater price pressure.
What is the geographic coverage and international risk?
Kevzara has international regulatory approvals, but market access varies by country. European markets are likely to experience biosimilar pressure through national reimbursement systems and tendering. The commercial effect can arrive before U.S. biosimilar launch because European payers often use centralized procurement and price competition.
The main geographic risks are:
- Earlier price erosion in European tender markets.
- Reference-pricing effects across countries.
- Local manufacturing or supply requirements.
- Different supplementary protection certificate outcomes.
- National patent litigation and injunction standards.
- Lower net pricing in emerging markets.
Sanofi’s global manufacturing and distribution infrastructure reduces supply risk, but biologic production remains dependent on validated cell lines, purification processes, fill-finish capacity, and cold-chain controls. Those manufacturing requirements create barriers to entry but do not prevent capable biosimilar manufacturers from competing.
What licensing deals govern sarilumab?
Sarilumab originated from the Sanofi-Regeneron collaboration. Sanofi has led global commercialization, while Regeneron contributed antibody discovery and development capabilities and receives economics under the collaboration agreement. The precise royalty, profit-sharing, and territory terms are not fully disclosed in routine product reporting. [2][3]
The collaboration structure affects valuation because Kevzara revenue is not equivalent to Sanofi standalone profit. Royalty or profit-sharing obligations reduce the amount retained by Sanofi, although the parties also share development and commercialization responsibilities.
What is the FDA regulatory status of Kevzara?
Kevzara remains an FDA-approved biologic for adults with moderately to severely active rheumatoid arthritis and for adults with polymyalgia rheumatica under the approved labeling. The product is not a vaccine, gene therapy, or interchangeable biosimilar. Any future biosimilar must receive a separate 351(k) approval. [1][6]
The polymyalgia rheumatica indication expands the product’s regulatory label but does not reset the original biologic exclusivity period. A new indication generally does not create a new 12-year reference-product exclusivity period.
Key Takeaways
- Sarilumab is marketed as Kevzara by Sanofi and Regeneron.
- Sales have grown to approximately €1.2 billion annually, based on Sanofi reporting.
- The 2023 U.S. polymyalgia rheumatica approval expanded the commercial opportunity.
- U.S. biologic exclusivity is generally expected to run to approximately May 2029.
- Kevzara is governed by the Purple Book and BPCIA, not the standard Orange Book and Paragraph IV framework.
- The main long-term threat is biosimilar competition, not conventional generic substitution.
- Formulation, device, manufacturing, and method-of-use patents may extend litigation leverage but are less likely to block all biosimilar entry.
- Actemra remains the principal IL-6 competitor because of its earlier launch, broader indications, and multiple delivery formats.
- Sanofi’s revenue exposure is material but modest relative to Dupixent.
- The most likely launch sequence is continued branded growth through the late 2020s, followed by price and volume pressure after biosimilar entry.
FAQs
Is sarilumab the same as tocilizumab?
No. Sarilumab and tocilizumab both block the IL-6 receptor, but they are different monoclonal antibodies marketed as Kevzara and Actemra, respectively.
Can a sarilumab biosimilar be automatically substituted at the pharmacy?
Not automatically. FDA biosimilar approval and FDA interchangeability designation are separate regulatory outcomes. State pharmacy-substitution laws also apply.
Does the polymyalgia rheumatica approval extend Kevzara’s exclusivity?
Generally, no. A new indication does not normally create a new 12-year U.S. biologic reference-product exclusivity period.
Is Kevzara included in the FDA Orange Book?
Kevzara is a biologic approved under a BLA and is principally tracked through the FDA Purple Book rather than the conventional Orange Book framework.
What is the largest financial risk to Kevzara?
The largest structural risk is multi-entrant biosimilar competition after the end of U.S. biologic exclusivity, compounded by payer pressure and competing biologics in rheumatoid arthritis.
References
-
U.S. Food and Drug Administration. (2023). Kevzara prescribing information. FDA.
-
Sanofi. (2024). Universal registration document and annual financial report 2023. Sanofi.
-
Sanofi. (2025). Universal registration document and annual financial report 2024. Sanofi.
-
U.S. Food and Drug Administration. (2024). Biosimilar and interchangeable products. FDA.
-
U.S. Food and Drug Administration. (2024). Purple Book: Database of licensed biological products. FDA.
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U.S. Food and Drug Administration. (2024). Questions and answers on biosimilar development and the BPCI Act. FDA.
