Litigation Details for Horizon Pharma Inc. v. Par Pharmaceutical Companies, Inc. (D. Del. 2013)

Horizon Pharma Inc. v. Par Pharmaceutical Companies, Inc. (D. Del. 2013)

Docket	1:13-cv-00102	Date Filed	2013-01-17
Court	District Court, D. Delaware	Date Terminated	2013-10-17
Cause	35:271 Patent Infringement	Assigned To	Leonard Philip Stark
Jury Demand	None	Referred To
Parties	PAR PHARMACEUTICAL COMPANIES, INC.
Patents	8,309,127; 8,318,202
Attorneys	Megan C. Haney
Firms	Richards, Layton & Finger, PA
Link to Docket	External link to docket

Details for Horizon Pharma Inc. v. Par Pharmaceutical Companies, Inc. (D. Del. 2013)

Date Filed	Document No.	Description	Snippet	Link To Document
2013-01-17				External link to document

Horizon Pharma Inc. v. Par Pharmaceutical Companies, Inc. Litigation Summary and Patent Analysis

Last updated: August 12, 2026

Horizon Pharma Inc. v. Par Pharmaceutical Companies, Inc., No. 1:13-cv-00102, was a Hatch-Waxman patent case in the U.S. District Court for the District of Delaware concerning Par's abbreviated new drug application for a generic version of Duexis, Horizon's fixed-dose ibuprofen and famotidine product. Horizon asserted U.S. Patent No. 6,926,907 after receiving a Paragraph IV certification. The case was part of a broader group of Duexis patent disputes involving other generic manufacturers.

The litigation ended through settlement rather than a reported merits judgment against Par. The public record establishes the asserted patent, the generic-drug pathway, and the settlement disposition. Publicly available docket materials do not provide a complete set of commercial settlement terms.

What drug and patents were involved in Horizon Pharma v. Par?

The case concerned Duexis, a prescription combination tablet containing ibuprofen and famotidine.

Item	Details
Brand	Duexis
Active ingredients	Ibuprofen and famotidine
Therapeutic category	NSAID analgesic and anti-inflammatory product with gastrointestinal risk-reduction therapy
NDA holder at the time	Horizon Pharma Inc.
Generic pathway	ANDA under the Hatch-Waxman Act
Defendant	Par Pharmaceutical Companies, Inc.
Court	U.S. District Court for the District of Delaware
Case number	1:13-cv-00102
Filing period	2013
Principal asserted patent	U.S. Patent No. 6,926,907
Disposition	Settlement and dismissal

U.S. Patent No. 6,926,907 covered pharmaceutical compositions combining an NSAID with an H2-receptor antagonist. The patent was central to several Duexis-related Paragraph IV cases, including litigation against Dr. Reddy's Laboratories and other generic applicants.

What did U.S. Patent No. 6,926,907 protect?

The '907 patent generally covered dosage forms combining:

1. An NSAID, including ibuprofen; and
2. An H2 antagonist, including famotidine.

The commercial objective was to administer the anti-inflammatory drug and acid-suppression component in a coordinated oral dosage form. The patent estate therefore addressed more than the active ingredients individually. Its value depended on the combination architecture, release characteristics, dosing relationship, and therapeutic use.

The patent was not a patent on ibuprofen or famotidine as standalone active ingredients. Those compounds were long established. The relevant IP position came from combining them in a pharmaceutical product designed for chronic NSAID users.

When did Horizon sue Par over generic Duexis?

Horizon filed the action in 2013 after receiving notice of Par's Paragraph IV certification. Under the Hatch-Waxman framework, a Paragraph IV notice alleging that a listed patent is invalid, unenforceable, or not infringed can trigger patent litigation by the NDA holder.

The filing date initiated the statutory 30-month stay of FDA approval, subject to the specific Orange Book and regulatory circumstances applicable to Par's ANDA. The stay prevented FDA approval of the ANDA during the statutory period unless the litigation was resolved earlier or another statutory event terminated the stay.

Horizon filed the case during a period when Duexis had meaningful commercial protection from its formulation and combination-product patent position. The case was one of multiple actions designed to prevent an unlicensed generic launch before the relevant patent barriers expired or were resolved.

What was Par's Paragraph IV challenge?

Par's ANDA challenge placed the '907 patent at issue under the standard Paragraph IV theories:

• The patent was invalid.
• The patent was not infringed by Par's proposed product.
• The patent was unenforceable, if supported by the factual record.

The exact litigation positions were defined by the complaint, Par's ANDA notice, pleadings, and later settlement papers. Because the case did not produce a reported merits opinion, the public record does not establish that the court adopted Par's invalidity or noninfringement arguments.

Par's challenge had commercial significance because a successful Paragraph IV case could have allowed generic Duexis approval before the nominal patent expiration date. A settlement instead converted the litigation into a negotiated market-entry arrangement.

How strong was Horizon's Duexis patent estate?

Horizon had a commercially meaningful patent position, but the estate was concentrated rather than broad in the manner of a biologic or platform technology portfolio.

Patent-strength assessment

Factor	Assessment
Product coverage	Strong for the patented ibuprofen-famotidine combination and related dosage-form concepts
Ingredient exclusivity	Weak, because ibuprofen and famotidine were long-established compounds
Formulation dependence	High
Paragraph IV exposure	High, because ANDA applicants could directly challenge the listed patents
Litigation durability	Mixed across defendants; the principal patent survived some validity challenges in related litigation
Biosimilar protection	Not applicable
Manufacturing complexity	Moderate; the product required a controlled combination dosage form but not biologic manufacturing
Geographic reach	Primarily U.S.-focused in this case
Commercial value	Dependent on prescription volume, reimbursement, and the timing of generic entry

In related Duexis litigation, the Federal Circuit affirmed the district court's determination that asserted claims of the '907 patent were not shown to be obvious. That decision strengthened Horizon's negotiating position against generic applicants, although it did not automatically decide the Par case because each action depended on the defendant's ANDA product, litigation record, and settlement terms. Horizon Pharma, Inc. v. Dr. Reddy's Laboratories, Inc., 839 F.3d 1374 (Fed. Cir. 2016).

What was the litigation outcome?

The Par case was resolved by settlement. There was no reported trial judgment or Federal Circuit merits decision in the Par action.

The practical outcome was:

• Par did not obtain an immediate at-risk generic launch through a court victory.
• Horizon avoided the cost and uncertainty of a full trial.
• The parties established a negotiated framework for resolving Par's patent challenge.
• The settlement preserved Horizon's ability to commercialize Duexis during at least part of the remaining patent term.
• The public docket did not disclose all economic, launch-date, supply, licensing, or exclusivity provisions.

A settlement does not constitute a judicial finding that the patent was valid, infringed, or enforceable. It also does not establish that Par's ANDA product would have infringed if the case had proceeded to judgment.

Did the settlement permit Par to launch generic Duexis?

The case disposition indicates that Par's launch rights were governed by the settlement rather than by a judgment invalidating the '907 patent.

Publicly available reporting and company disclosures concerning Duexis settlements generally describe negotiated entry rights or other commercial arrangements without publishing every term. The precise Par launch date, any license scope, royalty obligations, authorized-generic provisions, and restrictions on supply or distribution should not be inferred from the dismissal alone.

The settlement's commercial effect was therefore different from an invalidity judgment:

Scenario	Effect on Horizon
Horizon wins at trial	Par remains blocked until patent expiry or later authorization
Par wins on invalidity	Par may obtain FDA approval and launch subject to regulatory conditions
Par wins on noninfringement	Par may launch if FDA approval is otherwise available
Settlement	Entry timing and economic terms are privately negotiated
Patent expiration	Generic entry becomes available without reliance on the settlement license

What was the Orange Book status of Duexis?

Duexis was regulated as a small-molecule prescription drug under an NDA, not as a biologic. Its relevant patent protection was therefore handled through FDA Orange Book listings and Hatch-Waxman litigation.

The '907 patent was the principal patent associated with the Duexis litigation. Orange Book-listed patents can create a statutory approval delay when an ANDA applicant files a Paragraph IV certification and the NDA holder timely sues.

The Orange Book does not itself determine whether a patent is valid or infringed. It identifies patents submitted by the NDA holder and provides the regulatory framework for ANDA certification and approval timing. Court judgments, settlements, patent expiration, pediatric exclusivity, and other statutory events determine whether a listed patent ultimately blocks approval.

When did Duexis lose exclusivity?

Duexis did not have a single exclusivity date. Its protection consisted of several overlapping layers:

1. FDA regulatory exclusivity, if applicable;
2. Patent protection for the combination and dosage form;
3. The 30-month Paragraph IV stay;
4. Settlement-based restrictions on generic entry;
5. Commercial protection from physician adoption, reimbursement, and manufacturing scale.

The key patent term associated with the '907 patent extended into 2023, subject to patent-term adjustment and any applicable statutory extensions. The practical generic-entry date could therefore differ from the nominal patent expiration date because of settlement provisions, approval timing, first-filer rights, manufacturing readiness, or other regulatory issues.

Duexis was not protected by biologic exclusivity, and no biosimilar pathway applied. The relevant competitive threat was an ANDA generic, not a biosimilar.

What formulation patents protected Duexis?

Duexis protection centered on the co-formulated ibuprofen-famotidine dosage form. The relevant technical issues included:

• Co-administration of ibuprofen and famotidine in one oral product;
• Release of the components in a therapeutically useful manner;
• Dose ratio and pharmacologic coordination;
• Protection against NSAID-associated gastrointestinal effects;
• Physical and chemical compatibility within the dosage form.

The formulation strategy created a patent barrier even though the underlying active ingredients were old. This type of estate can be commercially effective when the brand product has a specific dosage architecture, but it is more vulnerable than a new chemical entity patent because ANDA applicants can attack obviousness, written description, enablement, claim construction, and noninfringement.

Did method-of-use patents affect the Par case?

The Par case is principally associated with the formulation and combination patent position surrounding Duexis, particularly the '907 patent. Method-of-use claims can create a separate layer of protection where the patented use is narrower than the product itself.

For Hatch-Waxman purposes, a generic applicant may use a section viii statement to carve out a patented method of use when the labeling permits a noninfringing indication. That mechanism is less useful where the asserted claims cover the dosage form or composition itself. A composition claim can block a product regardless of the use stated in the generic label.

The distinction matters in assessing generic entry. A successful method-of-use carve-out may allow approval, while a composition or formulation patent can continue to block the product as a whole.

Which companies challenged Horizon's Duexis patents?

Horizon faced a broader generic challenge landscape than the Par case alone suggests. Publicly reported litigation included actions involving:

• Par Pharmaceutical Companies, Inc.;
• Dr. Reddy's Laboratories;
• Other ANDA applicants seeking approval for generic ibuprofen-famotidine products.

The related Dr. Reddy's litigation reached the Federal Circuit and produced a published decision concerning the '907 patent. That opinion provides the strongest public judicial record on the patent's validity, but it should not be treated as the judgment in the Par action.

The competitive threat came from several potential generic suppliers. Multiple ANDA applicants increase the probability of eventual generic entry because a settlement with one defendant does not necessarily bind unrelated applicants.

What patent litigation affected Horizon's revenue exposure?

Duexis revenue was exposed to generic entry because the product relied on a combination formulation rather than exclusivity in the active ingredients. The main financial variables were:

• The number of approved ANDAs;
• The timing of settlement-authorized launch;
• Whether an authorized generic entered at the same time;
• Pharmacy benefit manager formulary treatment;
• Price erosion after generic entry;
• The ability of Horizon to shift prescribers to other products;
• The remaining life of related patents.

A single generic entrant can produce substantial price pressure in a small-molecule product. Multiple entrants typically accelerate erosion. The settlement postponed or controlled the immediate risk from Par but did not eliminate the broader post-expiration risk.

How does Duexis compare with biologic products facing biosimilar risk?

Duexis and biologic products have materially different exclusivity structures.

Issue	Duexis	Biologic
Regulatory pathway	ANDA	Biosimilar application under the Public Health Service Act
Patent listing	Orange Book	Patent disclosure and litigation framework differs
Product type	Small-molecule combination tablet	Biologic
Primary challenge	Paragraph IV	Biosimilar patent litigation and interchangeability issues
Manufacturing barrier	Formulation and tableting	Cell line, process, analytics, and manufacturing controls
Exclusivity risk	Generic substitution and price erosion	Biosimilar entry, interchangeability, and contracting
Key IP value	Composition and formulation claims	Product, formulation, process, and manufacturing claims

The Par litigation did not create biosimilar risk. It was a conventional small-molecule ANDA dispute.

What is the current legal significance of the case?

The case is significant for three reasons.

First, it illustrates the value and limits of formulation patents for a combination product. A patent covering an old drug combination can delay generic entry if its claims withstand validity challenges and the generic product cannot avoid infringement.

Second, it shows how a Paragraph IV challenge can create settlement leverage without producing a reported judgment. The absence of a merits opinion means the case should not be cited as a definitive ruling on Par's product.

Third, the related Federal Circuit decision provides evidence that the principal Duexis patent had litigation strength against at least one generic defendant. That strength improved Horizon's negotiating position but did not eliminate the risk of additional ANDA challenges, settlement-driven entry, or post-expiration competition.

Key Takeaways

• Horizon Pharma sued Par in 2013 over Par's ANDA for generic Duexis.
• Duexis contains ibuprofen and famotidine in a fixed-dose combination tablet.
• U.S. Patent No. 6,926,907 was the principal patent associated with the case.
• The patent protected combination and dosage-form concepts, not ibuprofen or famotidine as new chemical entities.
• The case ended through settlement and did not produce a reported merits judgment against Par.
• The settlement controlled Par's entry rights, but public materials do not disclose every commercial term.
• Related litigation against Dr. Reddy's resulted in a Federal Circuit decision upholding the patent against an obviousness challenge.
• The product faced generic, not biosimilar, competition.
• The patent estate's commercial strength depended on formulation claims, remaining patent term, ANDA timing, and the number of competing generic applicants.
• Duexis' primary patent protection extended into 2023, subject to applicable patent-term calculations and settlement provisions.

FAQs About Horizon Pharma v. Par Pharmaceutical

What was Horizon's brand drug in the Par patent case?

The brand drug was Duexis, a fixed-dose ibuprofen and famotidine tablet.

Was Horizon Pharma v. Par decided by a judge or jury?

The case was resolved by settlement and did not produce a reported trial verdict or appellate merits decision.

Was U.S. Patent No. 6,926,907 a new chemical entity patent?

No. The patent covered a pharmaceutical combination and dosage-form technology involving known active ingredients.

Could Par have launched generic Duexis before patent expiration?

Par's launch rights were governed by the settlement and FDA approval requirements. The public dismissal does not, by itself, establish an immediate launch right.

Did this case involve a biosimilar?

No. Duexis is a small-molecule combination product. The case involved an ANDA and Paragraph IV patent litigation under the Hatch-Waxman Act.

References

1. U.S. District Court for the District of Delaware. (2013). Horizon Pharma Inc. v. Par Pharmaceutical Companies, Inc., No. 1:13-cv-00102.

2. U.S. Patent and Trademark Office. (2005). U.S. Patent No. 6,926,907: Pharmaceutical compositions comprising an H2 antagonist and an NSAID.

3. U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations. Orange Book.

4. Horizon Pharma, Inc. v. Dr. Reddy's Laboratories, Inc., 839 F.3d 1374 (Fed. Cir. 2016).

5. Horizon Pharma plc. (2014). Annual report on Form 10-K. U.S. Securities and Exchange Commission.