Supernus v. MSN Pharmaceuticals: Viloxazine ER Patent Suit Dismissed Without Prejudice
Supernus Pharmaceuticals filed a six-patent infringement action in the District of Delaware against MSN Pharmaceuticals over generic viloxazine extended-release capsules (100 mg, 150 mg, 200 mg). The case was voluntarily dismissed without prejudice under FRCP 41(a) after just 98 days — leaving the door open for future litigation.
A six-patent ANDA salvo that ended before substantive merits review
On July 15, 2025, Supernus Pharmaceuticals, Inc. filed suit in the U.S. District Court for the District of Delaware against MSN Pharmaceuticals, Inc., asserting infringement of six U.S. patents arising from MSN’s ANDA filing for generic viloxazine extended-release capsules in 100 mg, 150 mg, and 200 mg strengths. The asserted patents — US12121523B2, US11324753B2, US9358204B2, US11458143B2, US9603853B2, and US9662338B2 — collectively cover formulation, composition, and method-of-treatment aspects of viloxazine ER, the active ingredient in Supernus’s branded ADHD product Qelbree.
The case closed on October 21, 2025, when Supernus invoked Federal Rule of Civil Procedure 41(a) to voluntarily dismiss its complaint without prejudice. That procedural posture means no merits ruling was issued: no claim construction, no invalidity finding, and no infringement determination. Critically, a without-prejudice dismissal does not extinguish Supernus’s ability to reassert these same patents against MSN in a future action, distinguishing this outcome sharply from a with-prejudice dismissal or a settlement with a release.
At 98 days, the resolution is notably swift for a multi-patent Hatch-Waxman dispute. Such early voluntary dismissals in ANDA litigation often suggest the parties reached a commercial resolution — such as a licensing arrangement or agreed market-entry date — though the public record is silent on any underlying agreement. Alternatively, a procedural or regulatory development affecting the ANDA itself could have mooted the litigation. The without-prejudice posture preserves optionality for Supernus, which may yet refile if commercial or regulatory circumstances shift.
Filing to Voluntary dismissal in 98 days
98 days — resolved well before the typical Hatch-Waxman 30-month stay window expires
Voluntarily dismissed: what FRCP 41(a) without prejudice means for both parties
FRCP 41(a): voluntary dismissal without court order
Under Federal Rule of Civil Procedure 41(a), a plaintiff may dismiss an action without a court order before the defendant serves an answer or a motion for summary judgment. This is a unilateral procedural right. The dismissal carries no merits ruling — no patent is invalidated, no infringement is adjudicated, and no liability is established. The ‘without prejudice’ designation is the default under 41(a) unless the parties stipulate otherwise.
No merits adjudicationThe public record does not specify a settlement release
A dismissal ‘without prejudice’ preserves the plaintiff’s right to refile the same claims in a future action, subject to applicable statutes of limitations. A dismissal ‘with prejudice’ would bar refiling permanently. Here, the verdict text expressly states ‘without prejudice,’ confirming Supernus retains full optionality. Whether a private licensing agreement or market-entry arrangement accompanied this dismissal is not disclosed in the public record — a common feature of Hatch-Waxman resolutions.
Refiling right preservedSupernus retains six live patents and freedom to refile
The without-prejudice dismissal means none of Supernus’s six asserted patents — covering composition, formulation, and method-of-treatment claims for viloxazine ER — have been adjudicated invalid or not infringed. Supernus’s IP estate remains intact. If MSN’s ANDA pathway or commercial plans change, Supernus can reassert these patents. The swift resolution also conserves Supernus’s litigation resources for enforcement actions against other generic filers.
Patent portfolio intactMSN faces no injunction — but patent cloud remains
MSN Pharmaceuticals avoids an adverse judgment and any injunctive bar on its generic viloxazine product. However, the six Supernus patents remain valid and enforceable. If MSN proceeds toward ANDA approval and commercial launch without a licensing arrangement, Supernus retains the right to refile — potentially triggering a new 30-month stay. The lack of any invalidity or non-infringement ruling means MSN has gained no legal protection from the dismissed action.
No clearance obtainedFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Supernus Pharmaceuticals, Inc. | Company | CNS-focused branded pharmaceutical company — holder of US12121523B2 and 5 further viloxazine ER patentsSearch in Eureka ↗ |
| Defendant | Msn Pharmaceuticals, Inc. | Company | Generic pharmaceutical manufacturer seeking ANDA approval for viloxazine extended-release capsulesSearch in Eureka ↗ |
| Plaintiff counsel | Edgar H. Haug | Attorney | Counsel for Supernus Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Francis DiGiovanni | Attorney | Counsel for Supernus Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Nicholas F. Giove | Attorney | Counsel for Supernus Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Thatcher A. Rahmeier | Attorney | Counsel for Supernus Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff law firm | Faegre Drinker Biddle & Reath LLP | Law Firm | Representing Supernus Pharmaceuticals, Inc.Search in Eureka ↗ |
| Presiding judge | Judge Jennifer L. Hall | Judge | Delaware District CourtSearch in Eureka ↗ |
Official order — verbatim text
The verdict text invokes FRCP 41(a) explicitly and specifies ‘without prejudice,’ which is dispositive: no court adjudication of infringement, validity, or enforceability occurred. The phrasing is unilateral — Supernus acted alone, consistent with an early-stage dismissal before MSN filed a responsive pleading. The absence of any stipulation or consent order means there is no public record of agreed terms. Both parties’ substantive legal positions remain entirely open.
US12121523B2 — viloxazine extended-release capsule formulations for ADHD
The six asserted patents span application dates from 2013 (US13/761757, issuing as US9358204B2) through 2022 (US17/896774, issuing as US12121523B2), reflecting a classic pharmaceutical lifecycle extension strategy built around viloxazine extended-release technology. The portfolio collectively covers the composition of viloxazine ER capsules, specific dosage strengths, formulation parameters governing extended-release behaviour, and method-of-treatment claims for ADHD. The breadth of this patent family — six granted patents across nearly a decade of prosecution — is consistent with Supernus’s strategy of maintaining layered exclusivity for Qelbree.
For generic manufacturers, this six-patent array creates a formidable clearance challenge: invalidating or designing around any single patent is insufficient if the remaining five remain enforceable. The most recently issued patent, US12121523B2, with a 2022 application date, likely carries the longest remaining term and may contain the broadest method claims, making it the highest-priority target for IPR petitioners. Competing CNS drug developers and ANDA filers should conduct independent FTO analysis across all six patents before committing capital to a generic viloxazine program.
Should your team run an FTO against the Supernus viloxazine ER patent portfolio?
Any pharmaceutical company developing, filing an ANDA for, or planning to commercialise generic viloxazine extended-release capsules in the United States should treat this six-patent portfolio as a primary FTO target. The without-prejudice dismissal of the MSN suit confirms these patents remain live and enforceable — Supernus has not surrendered any claims. Product teams launching in the 100 mg, 150 mg, or 200 mg dose segments face direct exposure to all six asserted patents.
PatSnap Eureka’s FTO Search Agent enables R&D and IP teams to map their formulation specifications against the claim language across all six Supernus viloxazine ER patents simultaneously. Eureka identifies prior art gaps, flags continuation families that may yield additional patents, and benchmarks claim scope against competing ANDA filings — giving patent counsel a structured foundation for clearance opinions and IPR petition strategy before a Paragraph IV certification triggers a new 30-month stay.
Run a freedom-to-operate analysis on US12121523B2 to assess your product’s exposure
Run FTO in Eureka →Similar Hatch-Waxman ANDA patent cases in the District of Delaware
Explore related pharmaceutical patent infringement cases involving ANDA filers and branded CNS drug portfolios litigated in the District of Delaware.
What this case signals for the branded ADHD pharmaceutical IP landscape
Six-patent ANDA suits resolved this quickly rarely reflect weakness — they more often reflect leverage being exercised off-court.
Without-prejudice dismissals in Hatch-Waxman are a negotiating signal, not a concession
A 98-day voluntary dismissal without prejudice in a multi-patent ANDA case is consistent with a negotiated resolution — agreed market-entry dates, royalty arrangements, or co-promotion deals. Patent counsel monitoring viloxazine ER competitors should treat this dismissal as a signal of active licensing activity, not patent vulnerability. The six asserted patents remain fully enforceable against any other generic filer.
MSN’s ANDA status remains unresolved in the public record — watch for refilings
Because no court-approved settlement or consent judgment was entered, there is no public term sheet governing MSN’s market entry. If MSN pursues commercial launch without a transparent licensing arrangement, a fresh infringement complaint — with a new 30-month stay clock — remains a live option for Supernus. In-house teams at generic manufacturers should model this scenario into their ANDA launch planning.
Supernus v Msn — key questions answered
Supernus asserted six U.S. patents: US12121523B2, US11324753B2, US9358204B2, US11458143B2, US9603853B2, and US9662338B2. All relate to viloxazine extended-release capsule formulations and methods of treatment for ADHD, corresponding to Supernus’s branded product Qelbree.
The public record does not disclose the reason. A without-prejudice voluntary dismissal under FRCP 41(a) is consistent with a negotiated resolution — such as an agreed market-entry date or licensing arrangement — but no settlement terms were filed with the court. The possibility of a regulatory or procedural development affecting MSN’s ANDA cannot be ruled out from the public record alone.
No. A dismissal without prejudice carries no merits ruling. None of the six asserted patents were adjudicated invalid or not infringed. All six remain granted, enforceable U.S. patents. Supernus retains the right to refile infringement claims against MSN or any other party based on these patents.
The dispute concerns MSN’s ANDA for generic viloxazine extended-release capsules in 100 mg, 150 mg, and 200 mg strengths — the generic equivalent of Supernus’s branded ADHD treatment Qelbree. The six asserted patents cover the formulation, composition, and therapeutic methods associated with viloxazine ER.
Yes. Because the dismissal was explicitly without prejudice, Supernus retains the legal right to file a new complaint asserting the same or different patents against MSN. If MSN proceeds to ANDA approval and commercial launch, a new complaint could trigger a fresh 30-month stay under Hatch-Waxman, subject to applicable statutory timing requirements.
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