Last updated: September 20, 2026
PAR Pharmaceutical’s 2020 Hatch-Waxman action against Amneal EU Limited concerned an ANDA for a generic version of Nymalize, PAR’s nimodipine oral solution. PAR alleged that Amneal’s proposed product would infringe patents covering nimodipine liquid formulations and related pharmaceutical compositions. The case was filed in the U.S. District Court for the District of New Jersey as Civil Action No. 3:20-cv-18322.
The dispute was an ANDA-based patent case triggered by Amneal’s Paragraph IV certification. The principal commercial issue was whether Amneal could obtain FDA approval and launch a generic nimodipine oral solution before expiration of PAR’s Orange Book-listed patent rights.
What drug and product were at issue in PAR v. Amneal?
The litigation involved Nymalize, a ready-to-use oral solution containing nimodipine, a dihydropyridine calcium-channel blocker. Nymalize is approved for reducing the severity of neurological deficits caused by subarachnoid hemorrhage from ruptured intracranial aneurysms.
| Item |
Information |
| Reference drug |
Nymalize |
| Active ingredient |
Nimodipine |
| Dosage form |
Oral solution |
| NDA holder |
PAR Pharmaceutical, Inc. |
| NDA |
NDA 203340 |
| FDA approval |
May 2013 |
| Generic pathway |
ANDA under the Hatch-Waxman Act |
| Defendant |
Amneal EU Limited |
| Court |
U.S. District Court for the District of New Jersey |
| Civil action |
3:20-cv-18322 |
| Filing year |
2020 |
Nymalize was commercially important because it eliminated the need to manipulate nimodipine capsules before administration through an enteral feeding tube. The product’s formulation and administration characteristics created the basis for PAR’s patent strategy.
What patents did PAR assert against Amneal?
The case involved PAR patents directed to nimodipine pharmaceutical compositions and oral-solution formulations. Public patent and Orange Book records identify the Nymalize patent estate as including the following U.S. patents:
| U.S. patent |
General subject matter |
Approximate listed expiration |
| 8,735,428 |
Nimodipine pharmaceutical composition and oral-solution technology |
2030 |
| 8,859,623 |
Related nimodipine composition and formulation claims |
2030 |
| 9,192,644 |
Continuation patent directed to related nimodipine formulations |
2030 |
The patents were part of a continuation-based portfolio. This structure allowed PAR to pursue overlapping claim sets covering the active ingredient, liquid vehicle, solubilization system, concentration, and administration characteristics.
The exact claims asserted in an ANDA case depend on Amneal’s Paragraph IV notice and the claims identified in the complaint. The case was not a dispute over a new chemical entity. It was a formulation and pharmaceutical-composition dispute involving a previously known active ingredient.
How did the Paragraph IV challenge trigger the lawsuit?
Amneal’s ANDA included Paragraph IV certifications asserting that the relevant PAR patents were invalid, unenforceable, or would not be infringed by Amneal’s proposed product. Under the Hatch-Waxman Act, PAR had 45 days after receiving the Paragraph IV notice to file an infringement action.
PAR filed the complaint in October 2020. The filing invoked the statutory 30-month stay, which generally prevents FDA approval of the challenged ANDA for up to 30 months unless the court resolves the case earlier or otherwise modifies the stay. The stay operates as a regulatory delay, not as a final determination that the patents are valid or infringed. [1]
The key legal questions were:
- Whether Amneal’s proposed nimodipine oral solution fell within the asserted composition claims.
- Whether the asserted claims were valid over prior art.
- Whether PAR could establish infringement based on the ANDA submission under 35 U.S.C. § 271(e)(2).
- Whether any settlement or judgment would control the timing of generic entry.
What was the litigation posture and outcome?
The case was a district-court ANDA action rather than a post-launch patent dispute. The public docket identifies the action as resolved without a reported merits judgment establishing that Amneal’s commercial product infringed valid patent claims.
The available record does not establish a publicly disclosed launch date for Amneal’s generic Nymalize product. Nor does the docket, standing alone, disclose the full economic terms of any resolution. Hatch-Waxman settlements commonly include confidential commercial provisions, a licensed-entry date, or restrictions tied to regulatory approval, but those terms cannot be inferred from the existence of a dismissal alone.
The litigation therefore did not produce a publicly reported invalidity judgment that would broadly eliminate PAR’s Nymalize patent estate. It also did not create a publicly reported Federal Circuit precedent defining the scope of the asserted nimodipine claims in this action.
What patent claims were commercially important?
The commercial value of PAR’s portfolio came from its focus on the finished dosage form rather than merely on nimodipine as a molecule.
Formulation protection
Formulation claims can cover the use of specified excipients, solvents, surfactants, stabilizers, or concentration ranges. For a liquid product, infringement can turn on the composition of the final solution, not the manufacturing process used to produce it.
A generic applicant may avoid literal infringement by changing an excipient or concentration. That strategy can create separate questions under the doctrine of equivalents, although prosecution history and claim construction can restrict the available scope.
Method-of-use protection
Nymalize’s approved use is tied to subarachnoid hemorrhage. Method-of-use claims can create a separate barrier if a generic applicant’s labeling instructs the same indication or administration method.
Amneal’s potential exposure depended on the ANDA labeling, package insert, and any proposed instructions for administration through an enteral tube. In ANDA litigation, the proposed label is central to the infringement analysis.
Manufacturing and process barriers
The formulation patents may also affect manufacturing freedom to operate. A generic manufacturer could design around a composition claim but still face risk if its process produces the claimed formulation or relies on protected steps. Manufacturing claims are often less visible in commercial analyses because they may not be listed in the Orange Book, yet they can remain relevant in a post-approval dispute.
What was the Orange Book status of Nymalize?
The Orange Book identifies patents submitted by an NDA holder as covering the drug, formulation, or method of use. Listed patents can trigger Paragraph IV litigation when an ANDA applicant seeks approval before the listed expiration date.
For Nymalize, the relevant patent estate included formulation and composition patents associated with nimodipine oral solution technology. The Orange Book listing did not itself establish validity or infringement. It provided the regulatory mechanism that enabled PAR to bring the case after Amneal’s Paragraph IV certification. [2]
Orange Book-listed patents should be distinguished from FDA exclusivity:
| Protection |
Function |
| Patent listing |
Identifies patent rights relevant to ANDA certification |
| 30-month stay |
Delays FDA approval after timely patent litigation |
| New-drug exclusivity |
Restricts FDA approval independently of patent rights |
| Pediatric exclusivity |
Can add six months to certain patent or exclusivity periods |
| Settlement entry date |
Contractual or court-recognized timing for generic launch |
Nymalize’s commercial protection was principally patent-based. The product’s 2013 approval date placed it well beyond the standard five-year new chemical entity exclusivity period by the time of the 2020 lawsuit.
When could Amneal or another generic enter the market?
A generic launch could occur through one of four principal routes:
- A court judgment holding the asserted patents invalid or not infringed.
- Expiration of the relevant patents.
- A settlement granting Amneal a license or agreed launch date.
- A design-around product that does not infringe the surviving claims.
Because the public record does not establish a definitive authorized-entry date, the case does not support a precise commercial launch forecast. The approximately 2030 expiration horizon associated with the principal Nymalize formulation patents remained the key outer boundary for ordinary patent-based protection, subject to patent-term adjustment, terminal disclaimers, regulatory exclusivity, and any later-issued continuation patents.
A settlement could have allowed entry before the nominal patent expiration date. Generic entry in that situation would depend on the settlement terms, FDA approval, manufacturing readiness, and any applicable first-filer or exclusivity rights.
How strong was PAR’s Nymalize patent estate?
PAR’s patent position was stronger than a single-patent product strategy because the portfolio used multiple related patents and claim categories. That structure increased litigation leverage and reduced the risk that one adverse claim construction would eliminate every relevant protection.
The principal strengths were:
- Multiple patents directed to related nimodipine formulations.
- Protection focused on the approved liquid dosage form.
- A regulatory framework that permitted a 30-month approval stay.
- Potential overlap between composition, formulation, administration, and method-of-use claims.
- A product-specific formulation that was commercially differentiated from conventional nimodipine capsules.
The main weaknesses were equally material:
- Nimodipine was a known active ingredient.
- Formulation claims face obviousness challenges when the prior art discloses liquid delivery, solubilization, or enteral administration.
- Generic applicants can pursue excipient, concentration, and labeling design-arounds.
- Patent expiration approached well before the end of the product’s commercial life.
- A settlement can transfer market-entry value to the generic applicant without a public merits ruling.
The portfolio was therefore commercially meaningful but not equivalent to compound-level exclusivity.
Did biosimilar risk apply to Nymalize?
No. Nymalize is a small-molecule drug, not a biologic. Amneal’s application proceeded through the ANDA pathway, not the abbreviated pathway for biosimilars under the Public Health Service Act.
The relevant competitive risks were generic substitution, Paragraph IV litigation, formulation design-around, authorized generic competition, and potential settlement entry. Biosimilar interchangeability and biologic reference-product exclusivity were not applicable.
Which companies could challenge PAR’s Nymalize patents?
Amneal was the defendant in the identified action. Other generic companies could challenge the same patents through separate ANDAs, depending on their filing dates, Paragraph IV certifications, formulation design, and regulatory strategy.
Potential competitors would include manufacturers with capabilities in:
- Oral liquid development.
- Solubilization of poorly water-soluble compounds.
- Unit-dose packaging.
- Enteral-tube administration products.
- Hospital and specialty-pharmacy distribution.
The commercial market is narrower than the broad oral solid-dose generic market because Nymalize is a specialized hospital and post-acute-care product. That can reduce the number of credible entrants while increasing the value of a first approved generic.
What revenue exposure did the litigation create?
The case exposed PAR to erosion of Nymalize revenue from generic substitution. The impact would depend on:
- The number of approved generic entrants.
- Whether Amneal received an authorized or licensed launch date.
- Hospital purchasing contracts.
- Generic substitution rules.
- Pricing discounts.
- Whether PAR launched or licensed an authorized generic.
- The extent to which clinicians continued to prefer the ready-to-use formulation.
A single generic entrant can produce substantial price erosion in a hospital product, although the rate may be slower where procurement contracts, clinical familiarity, and specialized distribution limit substitution.
The litigation also had strategic value beyond direct Nymalize sales. A favorable outcome could preserve pricing and reinforce PAR’s formulation patent strategy. A settlement could monetize the remaining patent term while reducing trial risk.
What is the practical litigation assessment?
PAR v. Amneal was a conventional but commercially significant formulation-based Hatch-Waxman case. PAR’s position rested on patent protection for the nimodipine oral-solution product rather than on exclusivity for nimodipine itself.
The case record does not show a publicly reported merits ruling invalidating the asserted patents or finding Amneal’s proposed product infringing. The principal unresolved commercial variable was the timing and terms of any generic entry. The case should therefore be analyzed as a resolved ANDA dispute with limited public disclosure of launch economics, not as a precedent that definitively validated or invalidated the Nymalize patent portfolio.
Key Takeaways
- PAR sued Amneal EU in the District of New Jersey in 2020 over an ANDA for generic Nymalize.
- Nymalize contains nimodipine and is supplied as a ready-to-use oral solution.
- The dispute centered on formulation and pharmaceutical-composition patents, including U.S. Patent Nos. 8,735,428, 8,859,623, and 9,192,644.
- The case was triggered by Amneal’s Paragraph IV certification.
- The litigation did not produce a publicly reported merits judgment broadly invalidating PAR’s patent estate.
- Nymalize is a small-molecule product, so biosimilar rules do not apply.
- Generic entry timing cannot be established from the public litigation record alone.
- The principal business risk was formulation-specific generic erosion before the approximate 2030 patent-expiration horizon.
FAQs About PAR Pharmaceutical v. Amneal EU
What was PAR Pharmaceutical v. Amneal EU about?
It was a Hatch-Waxman patent lawsuit involving Amneal’s proposed generic version of Nymalize, a nimodipine oral solution.
What is Nymalize used for?
Nymalize is used to reduce the severity of neurological deficits caused by subarachnoid hemorrhage from ruptured intracranial aneurysms.
Was Amneal’s product a biosimilar?
No. Amneal’s product was a small-molecule generic drug submitted through the ANDA pathway.
Did PAR obtain a permanent injunction against Amneal?
The public record does not show a reported merits judgment imposing a permanent injunction in the identified action.
When did the Nymalize patents expire?
The principal Nymalize formulation patents associated with the litigation had expiration dates generally reported around 2030, subject to patent-specific term calculations and applicable adjustments.
References
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U.S. Code. (2023). 21 U.S.C. § 355(j), abbreviated new drug applications and patent certifications.
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U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
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U.S. Patent and Trademark Office. (2024). Patent Center and Patent Examination Data System. https://patentcenter.uspto.gov
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U.S. District Court for the District of New Jersey. (2020). PAR Pharmaceutical, Inc. v. Amneal EU, Limited, No. 3:20-cv-18322.
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U.S. Food and Drug Administration. (2013). Nymalize prescribing information and NDA 203340 materials. https://www.accessdata.fda.gov/scripts/cder/daf/
