Alexion v. Samsung Bioepis: Six-Patent Eculizumab Biosimilar Dispute Dismissed Without Prejudice
Alexion Pharmaceuticals and its Irish affiliate brought a six-patent infringement action against Samsung Bioepis over SB12, a biosimilar of the blockbuster complement inhibitor SOLIRIS® (eculizumab). The Delaware District Court case closed after 244 days, dismissed without prejudice under a confidential August 2024 agreement — leaving all claims legally unresolved and re-fileable.
Alexion’s Six-Patent Biosimilar Blockade Against Samsung Bioepis SB12
On January 3, 2024, Alexion Pharmaceuticals, Inc. and Alexion Pharma International Operations Ltd. filed suit in the U.S. District Court for the District of Delaware before Judge Gregory B. Williams, asserting six patents against Samsung Bioepis Co., Ltd. The patents in suit — US10590189B2, US9725504B2, US9732149B2, US9718880B2, US10703809B1, and US9447176B2 — cover compositions and methods relating to eculizumab, the active ingredient in SOLIRIS®, one of the world’s highest-revenue rare disease biologics. The accused product is Samsung Bioepis’s SB12, its biosimilar version of SOLIRIS®.
The action was terminated on September 3, 2024, when the parties filed a Rule 41(a)(1)(A)(ii) stipulated dismissal without prejudice, citing a bilateral agreement executed on August 30, 2024. The dismissal is without prejudice, meaning no claim was decided on the merits and Alexion retains the right to reassert any or all of the six patents against Samsung Bioepis in future litigation. No costs, disbursements, or attorneys’ fees were awarded to either side. The court expressly retained jurisdiction to enforce and resolve disputes arising from the underlying agreement.
At 244 days, the case resolved quickly relative to multi-patent biologics disputes, which typically run two to four years in Delaware. The pre-trial timing and the court’s retained jurisdiction strongly suggest the parties reached a commercial settlement or licensing arrangement, though the specific terms remain confidential. What the public record cannot confirm is whether Samsung Bioepis obtained a licence to commercialise SB12 in the U.S., whether a launch date was agreed, or whether the resolution was conditional on FDA approval milestones.
Filing to Dismissed without Prejudice in 244 days
244 days — resolved before trial, faster than the median ANDA/biosimilar Delaware case
Dismissed without prejudice: what the stipulated exit means for both parties
Rule 41(a)(1)(A)(ii): stipulated dismissal, no merits ruling
A Rule 41(a)(1)(A)(ii) dismissal requires agreement from all parties and carries no judicial finding on validity, infringement, or enforceability. The six asserted patents remain presumptively valid. The court retained jurisdiction to enforce the parties’ private agreement, indicating a binding commercial deal underlies the exit — but the public record discloses no terms.
No merits adjudicationAlexion retains all six patents intact and re-filing rights
Because the dismissal is without prejudice, Alexion is not barred from re-filing infringement claims on any of the six patents against Samsung Bioepis. The patents emerge from this action with no adverse validity or infringement ruling. A without-prejudice dismissal differs critically from one with prejudice: the latter would bar future claims; the former leaves Alexion’s full enforcement options open, subject only to applicable statutes of limitations.
Enforcement options preservedSamsung Bioepis faces no injunction but no licence confirmed on the record
Samsung Bioepis avoided a merits judgment and secured an exit without any public admission of infringement. However, the without-prejudice nature means it cannot treat the dismissal as a clean bill of health on the six patents. If commercialisation of SB12 proceeds without a confirmed licence, Samsung Bioepis remains exposed to renewed infringement claims. The court’s retained jurisdiction adds an additional compliance dimension that is unusual in purely voluntary dismissals.
Latent re-filing riskConfidential deal structure signals a negotiated biosimilar market entry
The combination of pre-trial resolution, retained court jurisdiction, and zero-cost dismissal is consistent with a negotiated market-entry agreement — potentially a licensed launch with royalties or a delayed entry date. For the eculizumab biosimilar market, the outcome suggests Alexion is managing competitive entry commercially rather than through litigation wins. Rivals developing complement-inhibitor biosimilars should monitor any SB12 U.S. launch date as a proxy for the deal’s commercial parameters.
Negotiated market entry likelyFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Alexion Pharmaceuticals, Inc. | Company | Rare disease pharmaceutical company — holder of US10590189B2 and 5 eculizumab patentsSearch in Eureka ↗ |
| Co-Plaintiff | Alexion Pharma International Operations, Ltd. | Company | Search in Eureka ↗ |
| Defendant | Samsung Bioepis Co., Ltd. | Company | Samsung Bioepis Co., Ltd. — South Korean biosimilar developer, SB12 eculizumab biosimilarSearch in Eureka ↗ |
| Plaintiff counsel | Alexandra M. Joyce | Attorney | Counsel for Alexion Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Andrew J. Cochran | Attorney | Counsel for Alexion Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Daniel M. Silver | Attorney | Counsel for Alexion Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Gerald J. Flattmann , Jr. | Attorney | Counsel for Alexion Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Maliheh Zare | Attorney | Counsel for Alexion Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff law firm | McCarter & English LLP | Law Firm | Representing Alexion Pharmaceuticals, Inc.Search in Eureka ↗ |
| Defendant counsel | Andrew Colin Mayo | Attorney | Counsel for Samsung Bioepis Co., Ltd.Search in Eureka ↗ |
| Defendant counsel | Brianna Patterson | Attorney | Counsel for Samsung Bioepis Co., Ltd.Search in Eureka ↗ |
| Defendant counsel | Daniel J. Knauss | Attorney | Counsel for Samsung Bioepis Co., Ltd.Search in Eureka ↗ |
| Defendant counsel | James L. Higgins | Attorney | Counsel for Samsung Bioepis Co., Ltd.Search in Eureka ↗ |
| Defendant counsel | Jonathan R. Davies | Attorney | Counsel for Samsung Bioepis Co., Ltd.Search in Eureka ↗ |
| Defendant counsel | Michelle S. Rhyu | Attorney | Counsel for Samsung Bioepis Co., Ltd.Search in Eureka ↗ |
| Defendant counsel | Orion Armon | Attorney | Counsel for Samsung Bioepis Co., Ltd.Search in Eureka ↗ |
| Defendant law firm | Ashby & Geddes PC | Law Firm | Representing Samsung Bioepis Co., Ltd.Search in Eureka ↗ |
| Defendant law firm | Young, Conaway, Stargatt & Taylor LLP | Law Firm | Representing Samsung Bioepis Co., Ltd.Search in Eureka ↗ |
| Presiding judge | Judge Gregory B. Williams | Judge | Delaware District CourtSearch in Eureka ↗ |
Official order — verbatim text
The stipulated dismissal invokes Rule 41(a)(1)(A)(ii), which requires mutual consent and produces no judicial finding on the merits. The explicit retention of court jurisdiction over ‘the Agreement’ is the most legally consequential phrase in the verdict: it converts a private contract into a court-enforceable instrument, enabling either party to seek contempt or specific performance without initiating fresh litigation. The ‘without costs’ provision confirms neither party conceded liability as a condition of exit.
US10590189B2 — Eculizumab antibody compositions and related complement-inhibitor patents
The six patents in suit — US10590189B2, US9725504B2, US9732149B2, US9718880B2, US10703809B1, and US9447176B2 — collectively protect eculizumab, a humanised anti-C5 monoclonal antibody that blocks the complement cascade. Application filing dates span from 2011 (US13/128523, parent of US9447176B2) through 2020 (US16/804567, parent of US10703809B1), reflecting Alexion’s strategy of filing continuation and continuation-in-part applications to maintain layered protection across the SOLIRIS® product lifecycle. The technical domain encompasses antibody amino acid sequences, formulation compositions, and methods of treating complement-mediated diseases.
SOLIRIS® (eculizumab) generated multi-billion-dollar annual revenues for Alexion before AstraZeneca’s acquisition, making this portfolio one of the most commercially significant rare disease antibody estates in the U.S. The breadth of the six-patent estate — spanning structural, formulation, and method claims across multiple patent families — creates a high barrier for any biosimilar entrant. Competitors developing anti-C5 biosimilars must navigate not only FDA BPCIA requirements but also this layered patent thicket; a single non-infringing formulation or dosing approach may not escape all six claim sets simultaneously.
Should you run an FTO against the six eculizumab patents asserted in Alexion v. Samsung Bioepis?
Any company developing, manufacturing, or commercialising an eculizumab biosimilar — or any anti-C5 complement-inhibitor biologic — in the U.S. market should treat these six patents as a primary FTO target. The dismissal without prejudice means Alexion’s enforcement rights are fully intact. R&D teams designing around SOLIRIS® should assess claim scope across US9447176B2, US9718880B2, US9725504B2, US9732149B2, US10590189B2, and US10703809B1 simultaneously, as continuation relationships mean claim scope may be broader than any single patent suggests.
PatSnap Eureka’s FTO Search Agent can map your anti-C5 antibody sequence, formulation parameters, and dosing regimen against the independent and dependent claims across all six patents in a single workflow. Eureka surfaces prosecution history estoppel, continuation chain relationships, and prior art references that may support non-infringement or invalidity arguments — giving your IP and regulatory teams a consolidated risk picture before IND filing or biosimilar application submission.
Run a freedom-to-operate analysis on US10590189B2 to assess your product’s exposure
Run FTO in Eureka →Similar eculizumab and anti-C5 biosimilar patent cases in Delaware
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What this case signals for the eculizumab biosimilar IP landscape
A six-patent portfolio wielded pre-trial produced a confidential exit — a pattern worth studying for any biosimilar entrant targeting complement inhibitors.
Broad patent portfolios create negotiating leverage before trial
Alexion asserted six patents spanning compositions and methods, making claim-by-claim invalidity arguments expensive and uncertain. Multi-patent coverage — even if individual patents are vulnerable — typically shifts the economics toward settlement. Biosimilar developers entering high-value biologics markets should model full portfolio exposure, not individual patent risk.
Court-retained jurisdiction is a material term, not boilerplate
The stipulated dismissal explicitly preserves Delaware District Court jurisdiction over the parties’ private agreement. This gives Alexion a fast enforcement path if Samsung Bioepis breaches deal terms — without needing to re-file a new infringement action. Counsel structuring biosimilar settlements should treat retained jurisdiction clauses as a substantive commercial term with real enforcement teeth.
Alexion v Samsung — key questions answered
Alexion asserted six patents: US10590189B2, US9725504B2, US9732149B2, US9718880B2, US10703809B1, and US9447176B2. All relate to eculizumab (anti-C5 complement inhibitor) compositions and methods covering the SOLIRIS® biologic. The accused product was Samsung Bioepis’s SB12 biosimilar version of SOLIRIS®.
The parties filed a Rule 41(a)(1)(A)(ii) stipulated dismissal citing a bilateral agreement dated August 30, 2024. A without-prejudice dismissal carries no merits ruling and preserves Alexion’s right to re-file. The court retained jurisdiction to enforce the underlying agreement, which is consistent with a confidential commercial settlement or licensing arrangement, though no terms were disclosed publicly.
No. A dismissal without prejudice under Rule 41(a)(1)(A)(ii) produces no judicial finding on patent validity, infringement, or enforceability. All six patents remain presumptively valid. Alexion can assert them again in future litigation against Samsung Bioepis or other biosimilar developers without any adverse precedent from this action.
The stipulated dismissal expressly states that the Delaware District Court retains jurisdiction to enforce and resolve disputes under the parties’ August 2024 agreement. This is commercially significant: if either party breaches the deal, the aggrieved party can seek court enforcement without filing a new lawsuit. It effectively transforms the private agreement into a court-supervised arrangement, which is atypical of purely voluntary dismissals.
SB12 is Samsung Bioepis’s biosimilar candidate referencing SOLIRIS® (eculizumab), Alexion’s FDA-approved anti-C5 complement inhibitor used to treat rare diseases including paroxysmal nocturnal haemoglobinuria (PNH) and atypical haemolytic uraemic syndrome (aHUS). As a biosimilar, SB12 must demonstrate no clinically meaningful differences from the reference product while navigating the BPCIA patent dance process, which triggered this litigation.
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