Supernus v. Macleods: Six-Patent Viloxazine ER Suit Dismissed in 38 Days
Supernus Pharmaceuticals filed a six-patent infringement action in Delaware against Macleods Pharmaceuticals over generic viloxazine 150 mg and 200 mg extended-release capsules. The case closed just 38 days after filing when Supernus voluntarily dismissed without prejudice under Rule 41(a), leaving the door open for re-filing.
A rapid, pre-merits exit in a high-stakes ANDA patent fight
Supernus Pharmaceuticals, Inc. filed Case No. 1:25-cv-01146 in the Delaware District Court on 15 September 2025, asserting six patents against Macleods Pharmaceuticals over its proposed generic viloxazine extended-release capsules in 150 mg and 200 mg strengths. Viloxazine ER is marketed by Supernus as Qelbree, approved for attention-deficit/hyperactivity disorder (ADHD). The suit is consistent with standard Hatch-Waxman paragraph IV patent certification litigation triggered by Macleods’ ANDA filing with the FDA.
On 23 October 2025 — just 38 days after filing — Supernus invoked Federal Rule of Civil Procedure 41(a) to voluntarily dismiss its complaint without prejudice. A without-prejudice dismissal means the action is terminated but no adjudication on the merits has occurred; Supernus preserves the right to bring the same infringement claims against Macleods again in future proceedings. No defendant law firm had appeared on the public record, and no costs or fees were assessed.
The speed of resolution — 38 days, before any substantive court activity — strongly suggests the dismissal was strategic rather than indicative of a weakness in Supernus’s patent portfolio. Common drivers include parallel settlement negotiations, an out-of-court licensing arrangement, or a decision to wait for a more procedurally advantageous moment to re-file. The public record does not disclose whether any agreement was reached between the parties, and the without-prejudice nature means Macleods remains exposed to future suit on all six asserted patents.
Filing to Voluntary dismissal in 38 days
38 days — resolved before substantive motion practice, well below typical ANDA litigation timelines of 2–3 years
Voluntarily dismissed: what Rule 41(a) means for both parties
Rule 41(a) voluntary dismissal — no merits decided
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. The dismissal here was without prejudice, meaning no judgment was entered, no claims were adjudicated, and the underlying infringement allegations remain legally unresolved. The case is terminated procedurally, not substantively.
Pre-answer dismissalThe public record specifies ‘without prejudice’ — a critical distinction
A dismissal with prejudice bars re-filing the same claims permanently. A dismissal without prejudice — as explicitly stated here — preserves the plaintiff’s right to bring the same suit again. Supernus’s Rule 41(a) notice expressly states ‘without prejudice,’ so there is no ambiguity on this point: the litigation threat against Macleods on these six patents remains live.
Right to re-file preservedMacleods escapes this action — but remains exposed
Macleods obtains no declaratory judgment, no finding of non-infringement, and no invalidity ruling on any of the six asserted patents. The dismissal without prejudice provides no legal shield against a future Supernus suit on the same patents. If Macleods proceeds with its ANDA and launches commercially, it remains at risk of a new infringement action — potentially with a preliminary injunction motion attached.
No IP clearance obtainedSix-patent fortress around Qelbree remains legally intact
Supernus’s six-patent portfolio covering viloxazine ER has not been tested or weakened by this proceeding. For generic entrants, the without-prejudice dismissal provides no comfort: Supernus can re-file at any time before applicable statutes of limitations expire. Competitors and investors should treat the underlying patent claims as fully live and the ANDA pathway for viloxazine ER as still heavily encumbered.
Patent portfolio intactFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Supernus Pharmaceuticals, Inc. | Company | Specialty CNS pharmaceutical company — holder of US-9358204-B2 and five related viloxazine ER patentsSearch in Eureka ↗ |
| Defendant | Macleods Pharmaceuticals | Individual | Generic pharmaceutical manufacturer seeking ANDA approval for viloxazine ER 150 mg and 200 mg capsulesSearch in Eureka ↗ |
| Plaintiff counsel | Francis DiGiovanni | 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 dismissal notice invokes Rule 41(a) and explicitly specifies ‘without prejudice,’ leaving no interpretive ambiguity. No answer or summary judgment motion had been filed by Macleods, satisfying the procedural threshold for a unilateral plaintiff dismissal. Because no merits were adjudicated, the verdict carries no precedential weight on infringement or patent validity — the legal status of all six asserted patents is unchanged, and Supernus retains full enforcement rights against Macleods and other ANDA filers.
US-9358204-B2 and five related patents — viloxazine extended-release formulations
The six asserted patents — anchored by US-9358204-B2 and extending through US12121523B2, US11324753B2, US11458143B2, US9603853B2, and US9662338B2 — collectively protect Supernus’s viloxazine extended-release platform marketed as Qelbree. The portfolio spans formulation composition, extended-release delivery mechanisms, and method-of-treatment claims across multiple application families filed over several years, consistent with a deliberate lifecycle management strategy for an FDA-approved ADHD therapy.
For the generic pharmaceutical sector, this portfolio represents a multi-layered exclusivity barrier: a would-be generic entrant must clear not one but six patent families, each with potentially independent claim sets and expiry dates. The breadth of the portfolio — covering both the drug product and its therapeutic use — means that standard design-around strategies are materially more difficult. Any company pursuing an ANDA for viloxazine ER should conduct claim-by-claim analysis across all six patents before committing to a paragraph IV certification strategy.
Should your team run an FTO against Supernus’s viloxazine ER patent portfolio?
Any pharmaceutical company developing, manufacturing, or seeking ANDA approval for viloxazine extended-release capsules — in any strength — should treat this six-patent portfolio as an active enforcement risk. The without-prejudice dismissal in this case provides no FTO comfort. R&D and regulatory teams planning viloxazine ER generics, as well as formulation scientists working on norepinephrine reuptake inhibitor ER delivery platforms, should commission a full FTO analysis before advancing to IND or ANDA stages.
PatSnap Eureka’s FTO Search Agent allows you to map each of the six Supernus patents claim-by-claim against your proposed product design, identify prosecution history estoppel constraints, and flag related continuation applications that may not yet have issued. Eureka also monitors for new patent family members and Supernus portfolio additions in real time — critical intelligence when a brand pharmaceutical company has demonstrated willingness to assert a multi-patent stack in federal court.
Run a freedom-to-operate analysis on US-9358204-B2 to assess your product’s exposure
Run FTO in Eureka →Similar ANDA patent cases: viloxazine ER and CNS pharma in Delaware
Cases involving Hatch-Waxman patent assertions over CNS extended-release formulations in the Delaware District Court, including other Supernus enforcement actions.
What this case signals for the ADHD CNS pharmaceutical IP landscape
A 38-day without-prejudice exit on a six-patent ANDA suit is rarely a concession — it typically signals strategic repositioning.
Without-prejudice dismissals in ANDA cases often precede licensing deals
When a brand pharma plaintiff voluntarily exits a Hatch-Waxman suit within weeks, before any defendant appearance or substantive pleading, the most likely explanation is an out-of-court resolution — often a settlement with an authorised generic agreement or an entry date negotiation. The public record here is silent, but the pattern is well-established in ANDA litigation.
Macleods holds no IP clearance — market entry risk remains high
Generic manufacturers and their investors should note that a voluntary dismissal without prejudice provides zero legal protection. Macleods obtained no court finding on infringement, validity, or claim scope for any of the six Supernus patents. A commercial launch of viloxazine ER generics before Supernus re-files would carry significant at-risk exposure.
Supernus v Macleods — key questions answered
The dismissal without prejudice under Rule 41(a) means Supernus ended the case without any court ruling on the merits. No infringement or invalidity findings were made. Supernus retains the full right to re-file the same six-patent infringement claims against Macleods in future proceedings. Macleods obtained no legal protection or IP clearance from this dismissal.
Supernus asserted six patents: US-9358204-B2, US12121523B2, US11324753B2, US11458143B2, US9603853B2, and US9662338B2. All relate to viloxazine extended-release formulations and methods of treatment, covering Supernus’s Qelbree ADHD product. The portfolio spans multiple application families filed across several years.
The public record does not disclose the reason for the rapid dismissal. At 38 days, the case ended before any defendant appearance or substantive motion practice. Common drivers in ANDA litigation of this type include settlement negotiations, an authorised generic or market entry date agreement, or a strategic decision to refile at a more advantageous procedural moment. No official statement from either party is reflected in the public record.
The dismissal without prejudice provides Macleods no legal clearance to launch. All six Supernus patents remain fully enforceable, and Supernus may re-file at any time. A commercial launch by Macleods prior to a new settlement or a court finding of non-infringement or invalidity would carry material at-risk infringement exposure, including potential liability for lost profits or reasonable royalty damages.
The case was filed in the United States District Court for the District of Delaware and was assigned to Judge Jennifer L. Hall. Delaware is the most commonly selected venue for Hatch-Waxman ANDA patent litigation. Plaintiff counsel was Faegre Drinker Biddle & Reath LLP, represented by Francis DiGiovanni and Thatcher A. Rahmeier. No defendant counsel appeared on the public record before dismissal.
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