HORIZANT Drug Patent Profile

Which patents cover Horizant, and when can generic versions of Horizant launch?

Horizant is a drug marketed by Azurity and is included in one NDA. There are three patents protecting this drug and one Paragraph IV challenge.

This drug has seventy-three patent family members in twenty-four countries.

The generic ingredient in HORIZANT is gabapentin enacarbil. There are twenty-nine drug master file entries for this compound. One supplier is listed for this compound. Additional details are available on the gabapentin enacarbil profile page.

DrugPatentWatch^® Generic Entry Outlook for Horizant

Horizant was eligible for patent challenges on April 6, 2015.

By analyzing the patents and regulatory protections it appears that the earliest date for generic entry will be November 10, 2026. This may change due to patent challenges or generic licensing.

Annual sales in 2022 were $15mm indicating the motivation for generic entry (peak sales were $535mm in 2018).

There has been one patent litigation case involving the patents protecting this drug, indicating strong interest in generic launch. Recent data indicate that 63% of patent challenges are decided in favor of the generic patent challenger and that 54% of successful patent challengers promptly launch generic drugs.

There is one tentative approval for the generic drug (gabapentin enacarbil), which indicates the potential for near-term generic launch.

Indicators of Generic Entry

Summary for HORIZANT

International Patents:	73
US Patents:	3
Applicants:	1
NDAs:	1
Finished Product Suppliers / Packagers:	1
Raw Ingredient (Bulk) Api Vendors:	55
Clinical Trials:	16
Patent Applications:	376
Drug Prices:	Drug price information for HORIZANT
Drug Sales Revenues:	Drug sales revenues for HORIZANT
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for HORIZANT
What excipients (inactive ingredients) are in HORIZANT?	HORIZANT excipients list
DailyMed Link:	HORIZANT at DailyMed

See drug prices for HORIZANT

See drug sales revenues for HORIZANT

DrugPatentWatch^® Estimated Loss of Exclusivity (LOE) Date for HORIZANT

NDA:

022399

Dosage:

TABLET, EXTENDED RELEASE;ORAL

^*The generic entry opportunity date is the latter of the last compound-claiming patent and the last regulatory exclusivity protection. Many factors can influence early or later generic entry. This date is provided as a rough estimate of generic entry potential and should not be used as an independent source.

Recent Clinical Trials for HORIZANT

Identify potential brand extensions & 505(b)(2) entrants

Sponsor	Phase
Arbor Pharmaceuticals, Inc.	PHASE4
Azurity Pharmaceuticals	Phase 4
Massachusetts General Hospital	Phase 4

See all HORIZANT clinical trials

Pharmacology for HORIZANT

Physiological Effect

Decreased Central Nervous System Disorganized Electrical Activity

Paragraph IV (Patent) Challenges for HORIZANT

Tradename	Dosage	Ingredient	Strength	NDA	ANDAs Submitted	Submissiondate
HORIZANT	Extended-release Tablets	gabapentin enacarbil	300 mg and 600 mg	022399	1	2019-04-29

US Patents and Regulatory Information for HORIZANT

HORIZANT is protected by four US patents.

Generics may enter earlier, or later, based on new patent filings, patent extensions, patent invalidation, early generic licensing, generic entry preferences, and other factors.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-002	Dec 13, 2011		RX	Yes	No
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-001	Apr 6, 2011		RX	Yes	Yes
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-002	Dec 13, 2011		RX	Yes	No			Y	Y
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-001	Apr 6, 2011		RX	Yes	Yes			Y	Y
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-002	Dec 13, 2011		RX	Yes	No			Y
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-001	Apr 6, 2011		RX	Yes	Yes			Y

Expired US Patents for HORIZANT

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	Patent No.	Patent Expiration
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-002	Dec 13, 2011
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-001	Apr 6, 2011
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-002	Dec 13, 2011
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-002	Dec 13, 2011
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-001	Apr 6, 2011
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-001	Apr 6, 2011
Azurity	HORIZANT	gabapentin enacarbil	TABLET, EXTENDED RELEASE;ORAL	022399-001	Apr 6, 2011

International Patents for HORIZANT

See the table below for patents covering HORIZANT around the world.

Country	Patent Number	Title	Estimated Expiration
Austria	380029
Austria	540678
Australia	2002310409
Australia	2002345664
Australia	2003247522	METHODS FOR SYNTHESIS OF ACYLOXYALKYL DERIVATIVES OF GABA ANALOGS
Australia	2003297676	PRODRUGS OF GABA ANALOGS, COMPOSITIONS AND USES THEREOF
Australia	2007203364	Prodrugs of gaba analogs, compositions and uses thereof

Last updated: June 22, 2026

HORIZANT (gabapentin enacarbil) market dynamics and financial trajectory: pricing, demand, exclusivity, and generic risk

HORIZANT (gabapentin enacarbil) has remained a niche, specialty-market asset focused on two FDA-labeled indications: treatment of moderate-to-severe Restless Legs Syndrome (RLS) in adults and treatment of postherpetic neuralgia (PHN) in adults. Financial performance has tracked the standard pattern for a long-licensed, mid-to-lower market neurologic product: peak-era growth followed by value pressure from generic entry in the underlying gabapentin space, payer step edits, and use-site contracting that limits share. The nearer-term revenue profile hinges on (1) exclusivity and patent coverage through both the Orange Book and any formulation or method-of-use protection, and (2) whether generics can be launched without triggering product-specific IP barriers.

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What is HORIZANT’s labeled market and how big is the addressable population?

HORIZANT is marketed for:

• Restless Legs Syndrome (RLS) in adults (moderate-to-severe)
• Postherpetic Neuralgia (PHN) in adults

Which patient segments drive prescriptions

Commercial activity in both indications tends to concentrate in:

• Older adults (high RLS prevalence and PHN incidence after herpes zoster)
• Neurology and sleep-medicine prescribers for RLS
• Primary care and neurology for PHN
• Chronic medication users who stay on therapy if tolerability is acceptable and titration is managed

Demand sensitivity

• RLS is highly “managed care” in practice: payer criteria, step edits, and substitution pressure influence coverage.
• PHN is also payer-sensitive because many formularies prefer cheaper neuropathic options and only cover gabapentinoids after step therapy, especially where gabapentin is priced more aggressively.

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How do pricing and payer contracting dynamics affect HORIZANT revenue?

HORIZANT competes in a therapeutic class with gabapentin and pregabalin. Because those comparators are widely genericized, HORIZANT’s commercial price often faces direct coverage friction even when the product has pharmacokinetic positioning through prodrug delivery.

Main commercial levers

• Net price compression: Use of rebates, formulary placement, and dispensing-channel contracting drives net erosion even when list price changes are modest.
• Step edits and prior authorization (PA): Most meaningful in RLS and PHN where payers can justify switching to lower-cost gabapentin unless HORIZANT-specific criteria are met.
• Formulary tier placement: Neuropathic indications see frequent tier migration over time as payer models re-optimize benefit design.

What this means for financial trajectory

Even with steady physician familiarity, HORIZANT typically experiences:

• Flat-to-declining prescription growth when generic comparators gain share through payer substitution
• Revenue volatility driven less by clinical adoption and more by payer contracting cycles and channel inventory

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How has HORIZANT performed commercially vs generic gabapentin and pregabalin?

Competitive substitution pressure

The economic substitution problem is straightforward:

• Gabapentin and pregabalin are often covered at lower co-pays and are simpler to justify in PA forms.
• HORIZANT must defend its higher cost through formulary acceptance and patient-level tolerability/adherence differentiation.

Where HORIZANT can still hold share

• RLS patients who respond well to gabapentin enacarbil and tolerate the titration schedule
• PHN patients in whom clinicians avoid switching due to symptom stability
• Centers of practice with established neurologic protocols

Typical outcome over product life cycle

For products like HORIZANT:

• As generic alternatives remain dominant on formularies, HORIZANT’s growth tends to cap.
• Revenue becomes dependent on maintaining payer access and avoiding disruptive generic launches for HORIZANT itself.

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When does HORIZANT lose exclusivity based on patent and regulatory data?

Exclusivity structure affecting launch risk

HORIZANT’s ability to sustain premium pricing and stable demand depends on:

1. Patent exclusivity listed in the Orange Book for the marketed drug
2. Patent-protected formulation or method-of-use protections that can delay a true generic/ANDA launch
3. Any settlement frameworks following Paragraph IV filings (if present)

Because HORIZANT is a long-established product, the dominant question is not “does exclusivity exist,” but “does the Orange Book estate still block generic substitution of the specific drug product and strength/dosage form.”

Financial impact of exclusivity gaps

If exclusivity gaps open, revenue typically shifts in two phases:

• Pre-launch erosion: payer and channel begin stocking down and negotiating aggressive pricing.
• Post-launch step change: gross-to-net compresses, rebates increase, and prescription volume shifts to authorized generics or competitors.

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What patents protect HORIZANT and how strong is the patent estate?

How to evaluate strength for a specialty neurologic brand

Patent strength usually maps to:

• Composition of matter (highest barrier, longest reach)
• Formulation patents (can block bioavailability-equivalent generics)
• Method-of-use (can restrict “labeling” and limit interchangeability in practice)
• Manufacturing/process claims (can block manufacturing but may be harder to enforce depending on design-around)

Typical patterns in this class

For an orally administered prodrug antiepileptic-class product like gabapentin enacarbil, the most relevant barriers are usually:

• Formulation/controlled delivery concepts
• Salt/polymorph/form of the active
• Processes that control dissolution, absorption, or stability

What matters financially

In practice, the “strength” of the estate is not theoretical. It is whether competitors face:

• Injunction risk or threatened injunction at FDA approval and launch timing
• Settlement terms that preserve market share for a defined period
• Design-around feasibility that avoids infringement while keeping bioequivalence acceptable

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Is there Paragraph IV generic pressure against HORIZANT, and what launch scenarios are realistic?

Paragraph IV dynamics that move revenue

A Paragraph IV filing (or credible pathway signaling) typically causes:

• Accelerated contracting by PBMs
• Higher rebate pressure
• Earlier formulary switching even before launch if the filing is considered a credible path

Generic entry scenarios

For HORIZANT, the realistic competitive outcomes generally fall into:

• Authorized generic entry under license or settlement (fast uptake, deep price erosion)
• Full generic entry after court confirmation or agreed launch timing
• Delayed launch due to injunction (less likely as time passes, but can still occur if claim scope remains strong)

Financial trajectory implications

Even without an immediate launch, a credible Paragraph IV event can shift the revenue curve from “stable specialty” to “managed decline,” because payers price in post-expiration economics.

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What is the Orange Book status of HORIZANT?

The Orange Book status determines whether FDA-recognized patents and exclusivities cover:

• The listed active ingredient (gabapentin enacarbil)
• Specific dosage forms and strengths
• Whether there are patent term expirations by portion of the patent family

Why Orange Book status matters commercially

• PBMs and plan formularies rely on Orange Book listings to predict substitution timelines.
• Channel decision-makers use Orange Book data to manage inventory risk and negotiate pricing.

(Orange Book and patent listing specifics are the direct inputs into launch risk modeling. Those details are not reproduced here due to the need for exact listing fields and expiration-by-patent.)

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How does HORIZANT compete in RLS and PHN prescribing patterns?

RLS

RLS is a chronic condition where medication adherence and night-time symptom control can drive treatment persistence. Prescribing is influenced by:

• Comorbidities in older adults
• Side effect tolerance, especially sedation
• Iron status and other modifiable factors that can affect therapeutic choices

HORIZANT’s prodrug approach supports clinician preference in some cohorts, but payer substitution to cheaper gabapentin/pregabalin can limit expansion.

PHN

PHN prescriptions depend on:

• Disease course after shingles
• Timing relative to acute herpes zoster resolution
• Titration speed and neuropathic pain stability

Because multiple neuropathic options exist, HORIZANT competes on formulary positioning and clinical familiarity rather than being a last-line in most coverage models.

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What regulatory pathway issues shape HORIZANT’s future?

A generic or biosimilar pathway question is generally not the issue for HORIZANT because it is a small-molecule drug. The key regulatory determinants are:

• ANDA bioequivalence acceptability for the prodrug product
• Compliance with any labeled restrictions driven by method-of-use patents (if applicable)
• Whether competitors can maintain product integrity under manufacturing/process claims

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Which companies are positioned to benefit from HORIZANT exclusivity changes?

When exclusivity ends or is weakened via settlement or court outcomes, beneficiaries typically include:

• Generic manufacturers with ANDA portfolios aligned to oral solid dose prodrugs
• Authorized-generic partners that negotiate rapid market entry

The near-term winners are those that can launch quickly while sustaining acceptable reimbursement.

(Company-specific attribution requires a precise Orange Book-linked Paragraph IV record and ANDA approval status, which is not provided here.)

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What settlement agreements or litigation events influence HORIZANT market timing?

Patent litigation affects launch timing through:

• Automatic stays or injunction threats that delay ANDA effectiveness
• Settlement-driven “carve-outs” by date, strength, or formulation
• Agreement on marketing start that is often earlier than full litigation resolution but later than no-challenge scenarios

A shift from active litigation to settlement typically causes:

• A step change in payer contracting assumptions
• Channel inventory rationalization ahead of launch dates

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How many dosage forms and strengths affect generic entry risk?

HORIZANT’s generic risk is not uniform across strengths if:

• Patent coverage is strength-specific
• Formulation or manufacturing patents differ by dosage
• Labeling differs in relevant ways that affect method-of-use constraints

From a commercial standpoint, strength coverage influences how quickly substitution can occur because PBMs often target the highest-volume strength first.

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What manufacturing and IP barriers could slow HORIZANT generic substitution?

Key barriers for a prodrug oral product include:

• Ensuring consistent absorption profile and dissolution behavior
• Matching formulation and excipient systems used to achieve prodrug conversion
• Avoiding infringement on process claims related to stability, purification, or conversion steps

Even when composition patents expire, process/formulation patents can still create friction.

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How does HORIZANT’s financial trajectory typically look across the product life cycle?

Lifecycle pattern

For a mid-market specialty neurologic brand:

• Early growth: adoption in neurology and sleep clinics, early payer wins
• Maturity: stabilization with moderate prescription growth or plateau
• Late lifecycle: net price compression driven by generic competition in class and payer contracting
• Patent cliff risk: revenue drop if HORIZANT-specific generic barriers fall

Key revenue drivers to monitor

• Average net selling price and rebate rate trends
• Share of prescriptions vs gabapentin/pregabalin
• Patient persistence and treatment switch rates (especially from RLS)
• Inventory position in channel ahead of any exclusivity milestones

(Exact revenue figures and trajectory slopes are company- and payer-data dependent and are not stated here.)

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Key Takeaways

• HORIZANT is a specialty-priced gabapentin enacarbil product competing against widely genericized gabapentin and pregabalin, putting sustained pressure on net price via payer contracting and substitution.
• The financial trajectory is driven less by clinical conversion than by payer access, rebate dynamics, and the timing of any HORIZANT-specific Orange Book patent estate outcomes.
• Generic launch risk for HORIZANT hinges on patent/formulation barriers that can delay ANDA approval or limit substitution strength-by-strength.
• Monitoring Orange Book expirations, Paragraph IV litigation posture, and any settlement dates is essential to forecast revenue step changes and pre-launch erosion.

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FAQs

1. How do payer step edits for restless legs syndrome usually affect gabapentin enacarbil demand?
2. What Orange Book patent types most often delay generic entry for orally administered prodrugs like gabapentin enacarbil?
3. How do settlement timelines after Paragraph IV filings typically change HORIZANT net selling price before launch?
4. Do method-of-use patents for neuropathic pain products materially limit generic labeling substitution in practice?
5. Which RLS and PHN prescribing channels (neurology, sleep, primary care) tend to determine HORIZANT prescription persistence?

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References

1. FDA. Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book). U.S. Food and Drug Administration.
2. FDA. Guidance for Industry: Paragraph IV Certifications and Related Requirements Under the Drug Price Competition and Patent Term Restoration Act. U.S. Food and Drug Administration.

DrugChatter Q&A for HORIZANT

Why is horizant so expensive?
Does horizant have a generic?
Is there a generic for horizant?
Is horizant a controlled substance?
Horizant er 600 mg tablet?