Currax Pharmaceuticals v. Ajanta Pharma: SILENOR® Patent Dispute Dismissed Without Prejudice
Currax Pharmaceuticals LLC filed suit against Ajanta Pharma and its U.S. subsidiary over alleged infringement of 10 patents protecting its SILENOR® doxepin hydrochloride sleep tablets. The New Jersey District Court case closed after 322 days when both parties jointly stipulated to dismiss all claims, counterclaims, and defenses without prejudice, with each side bearing its own legal costs.
Ten-Patent SILENOR® Dispute Ends in Mutual Stipulated Dismissal
On July 24, 2023, Currax Pharmaceuticals LLC initiated infringement proceedings in the U.S. District Court for the District of New Jersey against Ajanta Pharma Limited and its U.S. subsidiary Ajanta Pharma USA Inc. The complaint centered on Ajanta’s proposed 3 mg and 6 mg doxepin hydrochloride oral tablets — a generic version of Currax’s branded SILENOR® sleep-disorder product — and asserted a broad portfolio of ten U.S. patents covering formulations and methods of use for low-dose doxepin.
The case concluded on June 10, 2024, when the court entered a stipulated order — consented to by all parties — dismissing all claims, counterclaims, and defenses without prejudice. Neither party was awarded attorneys’ fees or costs. The without-prejudice dismissal means no adjudication on the merits occurred: the patents were neither invalidated nor found infringed, and Currax retains the ability to reassert the same claims in future proceedings under appropriate circumstances.
The 322-day resolution is consistent with negotiated exits seen in Hatch-Waxman ANDA litigation, where brand and generic companies frequently reach confidential licensing or market-entry agreements that make continued litigation unnecessary. The public record is silent on whether any such commercial arrangement was reached here. The breadth of the asserted patent portfolio — ten patents spanning multiple application families — suggests Currax constructed a layered IP defence around SILENOR®, and the without-prejudice structure preserves that enforcement posture intact.
Filing to Dismissed without Prejudice in 322 days
322 days — resolved before trial in under 11 months, below the median ANDA patent case timeline
Stipulated dismissal without prejudice: what the order means for both sides
Dismissed without prejudice by joint stipulation
A without-prejudice dismissal by stipulation means the court ends the case at the parties’ mutual request without ruling on the merits. No finding of infringement, validity, or invalidity was made on any of the ten asserted patents. Because it is without prejudice, Currax is not barred from refiling the same claims — unlike a with-prejudice dismissal, which would preclude future enforcement of the same patents against the same accused products.
No merits adjudicationWithout prejudice vs. with prejudice — a critical distinction
The Verdict confirms dismissal ‘without prejudice,’ which preserves Currax’s right to bring future claims. A with-prejudice dismissal would have permanently barred re-litigation of the same patents against the same products. The public record does not disclose whether any licensing agreement, market-entry date, or settlement sum underpins the stipulation — that commercial context, if any, remains confidential.
Re-filing right preservedAjanta exits without an invalidity ruling — risk remains
Ajanta Pharma and its U.S. subsidiary secured dismissal of Currax’s infringement claims, but achieved no declaratory judgment of invalidity or non-infringement on any of the ten patents. This means the IP cloud over Ajanta’s proposed generic doxepin tablets persists. Any future commercial launch would need to account for the continuing enforceability of Currax’s patent portfolio unless a licensing or consent arrangement was reached privately.
No invalidity finding obtainedSILENOR® patent fortress remains legally intact post-dismissal
With ten patents neither invalidated nor adjudicated, Currax’s layered IP position around SILENOR® is commercially unweakened by this litigation. Other generic applicants contemplating ANDA filings for doxepin HCl tablets face the full breadth of this portfolio. The without-prejudice structure also signals that Currax may be willing to enforce again if a future generic entrant challenges the brand position without reaching a private arrangement.
Portfolio enforceability intactFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Currax Pharmaceuticals, LLC | Company | Pharmaceutical company — holder of US9107898B2 and 9 further SILENOR® doxepin patentsSearch in Eureka ↗ |
| Defendant | Ajanta Pharma | Individual | Indian generic pharmaceutical manufacturer and its U.S. subsidiary seeking to market generic doxepin HCl tabletsSearch in Eureka ↗ |
| Co-Defendant | Ajanta Pharma USA Inc. | Company | Search in Eureka ↗ |
| Plaintiff counsel | Hector Daniel Ruiz | Attorney | Counsel for Currax Pharmaceuticals, LLCSearch in Eureka ↗ |
| Plaintiff counsel | Jessica K. Formichella | Attorney | Counsel for Currax Pharmaceuticals, LLCSearch in Eureka ↗ |
| Plaintiff counsel | Liza M. Walsh | Attorney | Counsel for Currax Pharmaceuticals, LLCSearch in Eureka ↗ |
| Plaintiff counsel | Selena Miriam Ellis | Attorney | Counsel for Currax Pharmaceuticals, LLCSearch in Eureka ↗ |
| Plaintiff law firm | Walsh Pizzi O’Reilly Falanga LLP | Law Firm | Representing Currax Pharmaceuticals, LLCSearch in Eureka ↗ |
| Defendant counsel | Eric I. Abraham | Attorney | Counsel for Ajanta PharmaSearch in Eureka ↗ |
| Defendant counsel | Stephanie-Rose Orlando | Attorney | Counsel for Ajanta PharmaSearch in Eureka ↗ |
| Defendant counsel | William Murtha | Attorney | Counsel for Ajanta PharmaSearch in Eureka ↗ |
| Defendant law firm | Hill Wallack LLP | Law Firm | Representing Ajanta PharmaSearch in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | New Jersey District CourtSearch in Eureka ↗ |
Official order — verbatim text
The stipulated order dismisses ‘each of the parties’ claims, counterclaims and defenses without prejudice’ — language that is deliberately symmetrical, encompassing both Currax’s infringement assertions and Ajanta’s defensive counterclaims (which likely included invalidity and non-infringement counts). The explicit ‘without prejudice’ designation is legally significant: it leaves the IP dispute unresolved on the merits and preserves each party’s legal position. The mutual cost-bearing clause suggests neither side extracted litigation leverage sufficient to impose fee-shifting, consistent with a negotiated exit rather than a contested procedural defeat.
US9107898B2 and 9 further patents — low-dose doxepin HCl formulations for sleep disorders
The ten asserted patents — spanning application families filed from 2007 through 2020 — collectively protect the formulation, composition, dosing, and methods of use for low-dose doxepin hydrochloride oral tablets marketed as SILENOR®. Doxepin is a tricyclic compound historically used as an antidepressant; at the low doses covered by these patents (3 mg and 6 mg), it is indicated for insomnia characterised by difficulty with sleep maintenance. The portfolio’s chronological depth suggests iterative patent prosecution designed to extend IP coverage across multiple dimensions of the product.
Strategically, a ten-patent stack covering a single drug product creates a formidable barrier to generic entry. Each patent represents a potential infringement trigger and a separate IPR challenge, multiplying the cost and complexity for any ANDA challenger. For competitors in the sleep-disorder pharmaceutical sector, this portfolio signals that Currax has invested significantly in protecting SILENOR®’s commercial position and is prepared to litigate to defend it, as this filing against Ajanta demonstrates.
Should you run an FTO against the SILENOR® doxepin patent portfolio?
Any company developing, manufacturing, or seeking regulatory approval for a generic or reformulated low-dose doxepin hydrochloride oral tablet should conduct a comprehensive freedom-to-operate analysis against Currax’s ten-patent portfolio. The without-prejudice dismissal of this case means none of these patents have been invalidated or found non-infringed — the enforcement risk is fully intact. ANDA filers, 505(b)(2) applicants, and international generic manufacturers with U.S. distribution ambitions are all within the risk perimeter.
PatSnap Eureka’s FTO Search Agent can map each of the ten asserted patent families, identify claim-level coverage relevant to your specific formulation approach, and surface any post-grant proceedings or citation history that may affect enforceability. Running this analysis before an ANDA filing or product launch decision significantly reduces the risk of replicating Ajanta’s litigation exposure — particularly given that Currax has demonstrated willingness to assert the full portfolio.
Run a freedom-to-operate analysis on US9107898B2 to assess your product’s exposure
Run FTO in Eureka →Similar ANDA patent infringement cases involving doxepin and sleep-disorder formulations
Explore related Hatch-Waxman patent infringement actions in the D.N.J. and other federal courts involving low-dose doxepin HCl, SILENOR®, and sleep-disorder pharmaceutical IP.
What this case signals for the branded sleep-disorder pharma IP landscape
Ten asserted patents, a rapid exit, and zero cost-shifting — this case carries important signals for generic pharma entrants and ANDA filers.
Layered patent portfolios deter generic entry even without a trial win
Currax asserted ten patents across multiple application families, consistent with a strategy of maximising litigation cost and uncertainty for any generic challenger. Even without reaching trial or obtaining a court ruling, the breadth of the portfolio likely shaped Ajanta’s strategic calculus. R&D teams and generic IP counsel should map the full SILENOR® patent landscape before committing to an ANDA filing.
Without-prejudice exits preserve brand enforcement rights for future challengers
This dismissal neither confirms nor removes the patent barrier for the next generic entrant. Currax retains the right to sue any future ANDA filer on the same ten patents. In-house IP teams at generic companies should not treat this dismissal as evidence of a weakened patent position — the public record gives no indication of any concession by Currax.
Currax v Ajanta — key questions answered
Currax asserted ten U.S. patents: US9107898B2, US9486437B2, US10653662B2, US9861607B2, US8513299B2, US10238620B2, US7915307B2, US10653660B2, US11110074B2, and US9572814B2. All relate to low-dose doxepin hydrochloride oral tablet formulations and methods of use covering SILENOR® 3 mg and 6 mg tablets.
A without-prejudice dismissal does not bar Currax from refiling the same claims against Ajanta in the future. No merits determination was made — the patents were neither found valid nor invalid, and no infringement finding was entered. Currax retains its full enforcement rights against Ajanta or any other generic entrant targeting the same product.
The public record does not confirm a settlement. The case was dismissed by joint stipulation without prejudice, with each party bearing its own costs. This structure is consistent with a confidential commercial resolution — such as a licensing or consent agreement — but the court record does not disclose any such terms. An FTC consent-agreement filing, if required, could reveal additional context.
Multi-patent Hatch-Waxman suits are common brand strategy: listing multiple patents in the Orange Book and asserting the full portfolio maximises the automatic 30-month stay of ANDA approval and raises the cost of generic challenge. A broad assertion across formulation, composition, and method-of-use patents forces generic challengers to mount invalidity arguments on multiple fronts, increasing litigation burden and settlement leverage.
SILENOR® (doxepin HCl, 3 mg and 6 mg) is a low-dose tricyclic compound approved for treating insomnia characterised by sleep maintenance difficulty. Currax holds a layered portfolio of ten patents protecting it. Because this case ended without any invalidity ruling, the full patent barrier remains intact for any subsequent generic ANDA applicant, making FTO analysis essential before filing.
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