Supernus v. Ajanta Pharma: 10-Patent Oxcarbazepine Dispute Dismissed Without Prejudice
Supernus Pharmaceuticals filed suit against Ajanta Pharma in Delaware federal court, asserting 10 patents covering modified-release oxcarbazepine formulations used to treat seizures. After 447 days of litigation, both parties stipulated to dismiss all claims and counterclaims without prejudice, each bearing its own legal costs.
10-patent ANDA dispute over oxcarbazepine drops without prejudice in Delaware
On 28 October 2022, Supernus Pharmaceuticals, Inc. filed a patent infringement action against Ajanta Pharma Limited in the US District Court for the District of Delaware, presided over by Chief Judge Gregory B. Williams. Supernus asserted 10 US patents — spanning application dates from 2007 through 2021 — all directed to modified-release formulations of oxcarbazepine and methods of treating seizures using such formulations. The case is consistent with a Hatch-Waxman ANDA dispute, in which a branded pharmaceutical company challenges a generic manufacturer’s attempt to enter the market before patent expiry.
On 18 January 2024, after 447 days of litigation, Supernus and Ajanta jointly filed a stipulation under Federal Rule of Civil Procedure 41, dismissing all claims, counterclaims, and defenses without prejudice. The dismissal was mutual — covering both Supernus’s infringement claims and any invalidity or non-infringement counterclaims asserted by Ajanta. Crucially, each party agreed to bear its own legal costs and attorneys’ fees, suggesting a negotiated resolution rather than a unilateral capitulation by either side.
A dismissal without prejudice after more than a year of litigation in a multi-patent pharmaceutical case typically signals that the parties reached a private commercial agreement — potentially a settlement involving a market entry date, a licence, or a supply arrangement — the terms of which are not reflected in the public docket. The speed of resolution relative to the complexity of a 10-patent dispute may suggest that early claim construction or inter partes dynamics accelerated negotiation. What remains unknown is whether Ajanta agreed to delay market entry, received a licence, or withdrew its ANDA, all of which are common but confidential outcomes in Hatch-Waxman settlements.
Filing to voluntary dismissal in 447 days
447 days — from filing to stipulated dismissal in this 10-patent pharma dispute
What the without-prejudice stipulated dismissal means for both parties
Fed. R. Civ. P. 41 stipulated dismissal — both parties signed off
Under Rule 41, a stipulated dismissal requires agreement from all parties who have appeared. Here, both Supernus and Ajanta — through counsel — consented to dismiss all claims and counterclaims. This is distinct from a unilateral voluntary dismissal, and signals a negotiated exit rather than one party walking away. The mutual scope of the dismissal, covering defenses as well as claims, indicates a clean procedural close.
Bilateral stipulation under FRCP 41Without prejudice: Supernus can refile — but likely won’t need to
A dismissal without prejudice preserves Supernus’s right to bring the same infringement claims against Ajanta in future. In Hatch-Waxman litigation, this structure is common when parties settle commercially but want flexibility if the generic manufacturer later breaches a consent agreement or launches at risk. The public record does not disclose whether a confidential settlement agreement accompanies this dismissal, and no finding on the merits was made by the court.
No merits finding — claims preservedEach party bears its own costs — a hallmark of negotiated resolution
The explicit agreement that each party bears its own attorneys’ fees and costs is a standard feature of negotiated Hatch-Waxman settlements. Had one party prevailed procedurally or on a dispositive motion, fee-shifting might have been awarded. The symmetrical cost allocation here is consistent with a mutually acceptable commercial deal, and suggests neither party secured a dominant litigation position before settlement was reached.
Symmetric cost allocation10 patents asserted — broad formulation and method coverage
Supernus asserted 10 US patents with application dates ranging from 2007 (US11/734874) to 2021 (US17/238796), covering both composition-of-matter claims for oxcarbazepine modified-release preparations and method claims for treating seizures. This layered portfolio — spanning multiple patent families and expiry dates — is a deliberate Hatch-Waxman strategy designed to maximise the barriers to generic entry and extend commercial exclusivity across successive claim types.
10 patents, multiple familiesFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Supernus Pharmaceuticals, Inc. | Company | Specialty CNS pharmaceutical company — holder of US7722898B2 and 9 related oxcarbazepine patentsSearch in Eureka ↗ |
| Defendant | Ajanta Pharma Limited | Company | Indian generic pharmaceutical manufacturer seeking US market entry for oxcarbazepine formulationsSearch in Eureka ↗ |
| Plaintiff counsel | Anna N. Lukacher | Attorney | Counsel for Supernus Pharmaceuticals, Inc.Search in Eureka ↗ |
| Plaintiff counsel | Camille Y. Turner | Attorney | Counsel for Supernus Pharmaceuticals, Inc.Search 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 | Jason A. Kanter | 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 ↗ |
| Defendant counsel | Corey Weinstein | Attorney | Counsel for Ajanta Pharma LimitedSearch in Eureka ↗ |
| Defendant counsel | Kirby B. Drake | Attorney | Counsel for Ajanta Pharma LimitedSearch in Eureka ↗ |
| Defendant counsel | Neal Seth | Attorney | Counsel for Ajanta Pharma LimitedSearch in Eureka ↗ |
| Defendant counsel | Stamatios Stamoulis | Attorney | Counsel for Ajanta Pharma LimitedSearch in Eureka ↗ |
| Defendant counsel | Wesley E. Weeks | Attorney | Counsel for Ajanta Pharma LimitedSearch in Eureka ↗ |
| Presiding judge | Judge Gregory B. Williams | Chief Judge | Delaware District Court — Chief JudgeSearch in Eureka ↗ |
Stipulation of dismissal — official text
The stipulation dismisses all claims, counterclaims, and defenses without prejudice under FRCP 41, with each party bearing its own costs. This phrasing confirms no judicial ruling on infringement, validity, or enforceability was made. The mutual scope — explicitly covering Ajanta’s counterclaims as well as Supernus’s infringement claims — suggests a clean commercial resolution. Neither party obtained a legal advantage on the record, preserving both the patent portfolio’s enforceability and Ajanta’s ability to challenge validity in any future proceeding.
US7722898B2 and 9 further patents — modified-release oxcarbazepine formulations
The 10 asserted patents collectively protect Supernus’s proprietary technology for modified-release formulations of oxcarbazepine — an anticonvulsant used to treat partial-onset seizures — and the methods of treating seizures using such formulations. The portfolio spans application dates from 2007 (US11/734874) through 2021 (US17/238796), reflecting ongoing innovation in delivery system design, including extended-release mechanisms that improve tolerability and dosing convenience over immediate-release oxcarbazepine. The staggered application strategy is consistent with product lifecycle management in specialty CNS pharmaceuticals, designed to maintain exclusivity across successive patent families.
For generic manufacturers, this portfolio represents a substantial barrier. Each patent family must be independently challenged or designed around, and method-of-treatment claims can cover generic products even where composition claims are avoided. The inclusion of a 2021 application (US11166960B2) signals that Supernus continued to prosecute new claims well into the product’s commercial life, extending the potential litigation exposure for any ANDA filer. Competitors in the anticonvulsant space — particularly those developing modified-release neurological formulations — should treat this portfolio as a benchmark for the depth of IP protection that a sustained prosecution strategy can achieve.
Should you run an FTO against Supernus’s oxcarbazepine patent portfolio?
Any company developing modified-release formulations of oxcarbazepine — or closely related anticonvulsant compounds with similar release mechanisms — should conduct a freedom-to-operate analysis against this 10-patent portfolio before filing an ANDA or initiating clinical development. The portfolio covers both composition and method claims, meaning a product that avoids the formulation claims may still infringe method-of-treatment claims if used to treat seizures in the same indicated population. This is a particularly acute risk for 505(b)(2) applicants and generic filers targeting the US market.
PatSnap Eureka’s FTO Search Agent can map each of the 10 asserted patents against your product’s claim set, identify overlapping claim language across families, and flag prosecution history estoppel that may limit claim scope. Eureka’s claim monitoring alerts you when continuation or divisional applications from these families publish, so you are not caught off-guard by newly issued claims. Given that Supernus filed new applications as recently as 2021, active monitoring of this portfolio is essential for any team working in the modified-release CNS formulation space.
Run a freedom-to-operate analysis on US9119791B2 to assess your product’s exposure
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What this case signals for the CNS generic entry and pharma IP landscape
A 10-patent Hatch-Waxman dismissal without prejudice is rarely just a procedural event — it typically reflects a private commercial deal that reshapes generic market timing.
Multi-patent Hatch-Waxman filings deter generic entry even without trial
Supernus filed with 10 patents, triggering a 30-month stay on Ajanta’s ANDA approval. Even without reaching trial, the assertion of a large patent portfolio creates significant financial and regulatory friction for generic entrants. Branded companies in the CNS space routinely deploy this strategy to protect high-value formulation franchises well beyond the primary compound patent.
Without-prejudice dismissals preserve enforcement leverage for brand holders
By dismissing without prejudice, Supernus retains the ability to re-assert its 10 patents if Ajanta launches outside any agreed terms. This is a deliberate choice — it keeps the patent portfolio live as a deterrent. Generic manufacturers entering settlements in this structure should ensure any agreed market entry date or licence is clearly defined to avoid re-litigation risk.
Supernus v Ajanta — key questions answered
Supernus asserted 10 US patents: US7722898B2, US7910131B2, US8617600B2, US8821930B2, US9119791B2, US9351975B2, US9370525B2, US9855278B2, US10220042B2, and US11166960B2 — all covering modified-release oxcarbazepine formulations and methods of treating seizures. The case was filed in Delaware District Court on 28 October 2022.
The parties filed a joint stipulation under FRCP 41 on 18 January 2024 dismissing all claims, counterclaims, and defenses without prejudice, with each party bearing its own costs. The public record does not disclose the reason, but this structure is consistent with a confidential commercial settlement — common in Hatch-Waxman litigation — that may have included an agreed market entry date or licence.
A dismissal without prejudice means no judgment on the merits was entered, and the plaintiff retains the right to refile the same claims in future. In Hatch-Waxman disputes, this is frequently paired with a private settlement in which the generic manufacturer agrees to delay market entry. The patents remain valid and enforceable, and the brand holder can re-assert them if the terms of any agreement are breached.
Oxcarbazepine is an anticonvulsant used to treat partial-onset seizures. While the compound itself is not novel, modified-release delivery systems — which control drug absorption rate to improve tolerability and allow once-daily dosing — can attract separate patent protection. Supernus’s portfolio covers specific formulation technologies and treatment methods, providing IP coverage that extends beyond the compound patent.
The case lasted 447 days from filing (28 October 2022) to dismissal (18 January 2024). For a 10-patent Hatch-Waxman suit in Delaware, resolution before trial in under 15 months is relatively swift, suggesting early settlement negotiations. Many comparable multi-patent ANDA disputes in Delaware proceed to claim construction — and sometimes trial — over 2–4 years before resolution.
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