US Patent 8,252,332: Gabapentin Extended-Release Patent Scope, Claims and Competitive Landscape

US Patent No. 8,252,332 covers oral gabapentin matrix dosage forms engineered for prolonged release in the upper gastrointestinal tract, delayed peak exposure, reduced maximum plasma concentration, and preserved systemic exposure. The principal commercial relevance is Gralise, an extended-release gabapentin product developed by Depomed, now associated with Assertio Therapeutics. The patent is directed to pharmacokinetic performance, not merely to the presence of gabapentin in a sustained-release tablet.

What does US Patent 8,252,332 protect?

The patent protects a gabapentin dosage form that satisfies several limitations simultaneously:

Claim element	Scope
Active ingredient	Gabapentin
Dosage architecture	Matrix dosage form
Release site	Upper gastrointestinal tract
Release duration	About 5 to 12 hours
Peak concentration	Lower than an equal-dose immediate-release product
Bioavailability	At least 80% of the immediate-release comparator, measured by AUCinf
Dosage strength	Broadly claim 1: gabapentin; dependent claims: 300 mg or 600 mg
Matrix type	Polymer matrix, including a swellable hydrophilic polymer
Release mechanism	Diffusion from the polymer matrix
Pharmacokinetic timing	Longer Tmax than immediate release; selected claims require Tmax of at least approximately 5.6 hours
Therapeutic use	Treatment of pain, including neuropathic pain

The claims require a product to meet both structural and performance limitations. A tablet containing gabapentin in a polymer matrix is not automatically within the claims. The product must also produce the specified gastrointestinal release and pharmacokinetic profile.

How are the independent claims structured?

The patent contains three principal claim categories.

Dosage-form claims

Claims 1, 7, 22 and 23 cover the physical dosage form. Claims 1 and 7 require a lower maximum plasma concentration than immediate release. Claims 22 and 23 instead require a longer time to maximum plasma concentration.

Claim 7 is narrower than claim 1 because it specifies either:

one 600 mg dosage form; or
two 300 mg dosage forms.

The 300 mg and 600 mg limitations are commercially important because they correspond to the strengths used for Gralise titration and maintenance dosing.

Method-of-treatment claims

Claims 12 and 24 cover oral administration of the claimed dosage form to treat a condition responsive to gabapentin. Claims 16 and 17 narrow the indication to pain and neuropathic pain.

These claims may create infringement exposure for a generic manufacturer if the approved labeling directs use of the product for neuropathic pain or another patented indication. The practical risk depends on the relationship between the product label, the ANDA certification, the product’s actual formulation, and the scope of any remaining enforceable claims.

Dependent formulation and pharmacokinetic claims

Claims 4 to 6 and 9 to 11 narrow the matrix technology to:

a polymer matrix;
a swellable, hydrophilic polymer; and
diffusion-controlled release.

Claims 18, 20 and 21 add a maximum plasma concentration of at least approximately 3 micrograms per milliliter. Claim 19 adds a concentration-ratio limitation: the maximum plasma concentration divided by the concentration at 15 hours must be no more than approximately 2.

These limitations are directed to maintaining meaningful exposure while avoiding the high peak-to-trough profile associated with immediate-release gabapentin.

What is the core inventive concept?

The commercial and technical center of the patent is a gastroretentive or upper-gastrointestinal controlled-release approach to gabapentin.

Immediate-release gabapentin has dose-dependent absorption limitations and a relatively short effective absorption window. The claimed dosage form attempts to release gabapentin gradually in the upper gastrointestinal tract, where absorption is more favorable, while maintaining at least 80% of the immediate-release AUC.

The invention therefore combines three objectives:

prolonging release;
delaying or reducing the plasma peak; and
preserving overall exposure.

A formulation that merely slows dissolution but releases gabapentin after it has passed beyond the principal absorption region could fail the claimed bioavailability requirement. Conversely, a formulation with adequate AUC but no meaningful delay in Tmax or reduction in Cmax could fail the pharmacokinetic limitations.

What are the strongest claim limitations?

The most consequential limitations are the comparative pharmacokinetic requirements.

Five-to-12-hour release window

The dosage form must release gabapentin into the upper gastrointestinal tract over about 5 to 12 hours. The phrase is functional and may require evidence from dissolution testing, gastrointestinal transit data, pharmacokinetic studies, or a combination of those records.

A generic product with a conventional hydrophilic matrix could face a claim issue even if its excipient composition differs, provided it delivers the claimed performance.

AUC threshold

The product must achieve bioavailability of at least 80% of an equal-dose immediate-release dosage form, measured by AUCinf.

This requirement limits the claims to products that preserve systemic exposure. A low-dose or excessively slow-release product could avoid the claims if it does not reach the AUC threshold, although it might then fail to qualify as therapeutically substitutable for the reference product.

Lower Cmax or longer Tmax

The first group of claims requires a lower Cmax than immediate release. The second group requires a longer Tmax. These are alternative pharmacokinetic routes into the claim set.

A product could potentially avoid the lower-Cmax claims while still implicating the longer-Tmax claims, or vice versa, depending on its clinical data.

Upper-gastrointestinal release

The claims do not broadly cover every extended-release gabapentin product. They focus on release into the upper gastrointestinal tract. This limitation distinguishes the claimed technology from a dosage form designed primarily for colonic delivery or indiscriminate extended release throughout the gastrointestinal tract.

How broad are claims 1 and 22?

Claim 1 is broad in dosage-form architecture but narrow in performance. It does not expressly require a polymer matrix, a 300 mg or 600 mg strength, or diffusion-based release. Those limitations appear in dependent claims.

Claim 22 is similar but substitutes a longer Tmax requirement for the lower-Cmax requirement. This creates a separate infringement theory for products that delay peak concentration without necessarily demonstrating the precise lower-Cmax relationship required by claim 1.

The claim set is therefore layered:

Layer	Protection
Broadest	Gabapentin matrix dosage form with specified upper-GI release and AUC
Pharmacokinetic alternative	Longer Tmax than immediate release
Strength-specific	300 mg or 600 mg
Structural	Polymer matrix
Materials	Swellable hydrophilic polymer
Mechanism	Diffusion-controlled release
Clinical	Pain and neuropathic pain
Exposure profile	Cmax of at least about 3 µg/mL; Cmax-to-15-hour ratio no more than about 2

What formulations are protected by US 8,252,332?

The patent is most directly relevant to matrix tablets using hydrophilic polymers that swell after ingestion and control gabapentin diffusion. Potentially relevant materials include cellulose-derived polymers and other swellable polymers used in hydrophilic matrix systems.

The claims do not require a specific polymer, polymer concentration, tablet geometry, coating, manufacturing process, or excipient ratio. That increases the potential scope of the independent claims but also makes infringement dependent on demonstrating the claimed release and pharmacokinetic results.

A product could remain exposed even if it changes:

the polymer identity;
tablet compression force;
coating system;
excipient grade;
granulation process; or
tablet dimensions.

The change would matter if it altered the claimed clinical or release performance.

How does the patent compare with conventional gabapentin patent protection?

Gabapentin itself is an old small-molecule active ingredient. The principal exclusivity value in this patent is therefore not compound composition. It is delivery technology.

Protection category	Relevance to US 8,252,332
Gabapentin compound patent	Generally outside the patent’s central scope
Immediate-release capsule or tablet	Usually outside the claims
Extended-release matrix	Central technology
Upper-GI release	Express claim limitation
Pharmacokinetic profile	Central infringement issue
Pain treatment	Covered in method claims
Manufacturing process	Not the primary claim focus
Product-specific strength	Covered through 300 mg and 600 mg dependent claims

The patent should be analyzed with related controlled-release gabapentin patents, including earlier and later continuation or divisional filings. A competitor may avoid one patent while remaining exposed to another family member with different formulation, release, or method claims.

What is the Orange Book status of the patent?

Gralise is an FDA-approved extended-release gabapentin product. The FDA approved Gralise for the management of postherpetic neuralgia in adults. FDA approval occurred in January 2011 under NDA 022544. Gralise is a small-molecule drug, so biosimilar regulation is not applicable.

US 8,252,332 is part of the intellectual-property estate associated with controlled-release gabapentin products. Orange Book-listed patent status must be evaluated by NDA, product strength, listing date, patent-use code, and current FDA listing data. The existence of a patent in the Orange Book does not by itself establish that every claim covers every generic gabapentin product.

For litigation and launch analysis, the relevant questions are:

whether the patent is currently listed against the relevant Gralise NDA;
the expiration date recorded by FDA;
whether pediatric exclusivity extends the listed date;
the applicable patent-use code;
whether an ANDA applicant made a Paragraph IV certification; and
whether the NDA holder filed a timely infringement action.

When does US 8,252,332 lose exclusivity?

The ordinary patent term is generally 20 years from the earliest effective nonprovisional priority date, subject to patent-term adjustment, patent-term extension, terminal disclaimers and pediatric exclusivity.

Public drug-patent databases have associated the Gralise controlled-release patent family with expirations in the mid-2020s, but the controlling date for US 8,252,332 is the USPTO patent-term calculation and the current FDA Orange Book entry. A patent expiration date cannot be determined solely from the issue date of August 28, 2012.

The commercial exclusivity timeline has several distinct components:

Event	Date or status
US 8,252,332 issued	August 28, 2012
Gralise FDA approval	January 2011
Small-molecule regulatory exclusivity	Expired before the current patent-risk period
Patent exclusivity	Governed by the listed patent-term date
Generic pathway	ANDA, with Paragraph IV risk for listed patents
Biosimilar pathway	Not applicable

A generic launch analysis should use the latest USPTO Patent Center record and current Orange Book data rather than relying on the issue date or third-party database summaries.

Which companies have challenged Gralise or related gabapentin patents?

Generic-drug companies have had commercial incentives to challenge Gralise because the product uses a differentiated extended-release formulation rather than conventional immediate-release gabapentin.

Potential challengers in the market have included major ANDA sponsors such as Actavis, Par Pharmaceutical and Teva, depending on the specific patent, dosage form and litigation proceeding. The relevant case record must be separated by:

patent number;
defendant;
ANDA number;
product strength;
Paragraph IV certification;
district court outcome;
Federal Circuit status; and
settlement or launch agreement.

A Paragraph IV filing is an assertion that a listed patent is invalid, unenforceable or not infringed. It does not itself invalidate the patent or establish a right to launch.

What patent litigation affects the patent?

The most important litigation issues for this claim set would likely include:

Claim construction

Courts may need to interpret:

“upper gastrointestinal tract”;
“over about 5-12 hours”;
“at a rate sufficient”;
“lower maximum plasma concentration”;
“longer time to the maximum plasma concentration”; and
“at least 80%” bioavailability.

These limitations can create disputes over whether the claims require direct in vivo proof, in vitro release testing, or both.

Infringement testing

A patent holder would likely compare the accused product’s:

dissolution profile;
release location;
Cmax;
Tmax;
AUCinf;
dosage strength; and
labeling.

A product can satisfy the claim through inherent properties if those properties necessarily result from the accused formulation and administration method.

Validity

A challenger may rely on prior art involving:

sustained-release gabapentin;
hydrophilic matrix tablets;
gastroretentive delivery;
controlled release in the upper gastrointestinal tract;
gabapentin pharmacokinetics; and
comparative Cmax, Tmax and AUC data.

The strongest validity arguments would target the combination of known matrix technology with known gabapentin absorption behavior. The patent holder’s counterargument would focus on the claimed pharmacokinetic balance, particularly the preservation of at least 80% AUC while reducing peak exposure and extending Tmax.

How strong is the patent estate?

US 8,252,332 has meaningful commercial relevance because it covers the product-defining feature of a branded extended-release gabapentin product. Its strength is highest against products that:

use 300 mg or 600 mg strengths;
rely on a swellable hydrophilic matrix;
release gabapentin over a similar five-to-12-hour interval;
are labeled for neuropathic pain; and
demonstrate comparable AUC, Cmax and Tmax.

Its strength is lower against:

nonmatrix delivery systems;
depot or multiparticulate technologies with materially different release behavior;
products that do not release in the upper gastrointestinal tract;
formulations with substantially lower bioavailability; or
products whose labeling omits the patented method of use.

The performance limitations can strengthen validity by distinguishing the claimed formulation from generic sustained-release concepts. They can also make infringement more difficult to prove because product testing and clinical pharmacokinetic evidence become central.

What generic launch risks exist?

A generic manufacturer faces four principal launch scenarios.

Scenario	Commercial consequence
Patent challenge fails	Launch is blocked until patent expiry or settlement date
Patent invalidated or not infringed	Potential launch, subject to other listed patents
Settlement permits later launch	Entry date depends on agreement terms
Label carve-out succeeds	Narrower launch may be possible if patented use is removed

A successful Paragraph IV challenge to US 8,252,332 may not clear the entire Gralise estate. Related patents can independently block approval or create litigation exposure. Conversely, a patent settlement may resolve one patent while leaving other patents in force.

What manufacturing and IP barriers remain?

The manufacturing process may be easier to design around than the product performance claims because the asserted claims focus primarily on the dosage form and its effect after ingestion.

The principal barriers are:

reproducing adequate upper-GI residence or release;
achieving at least 80% relative AUC;
controlling Cmax;
delaying Tmax;
maintaining dose uniformity at 300 mg and 600 mg;
demonstrating pharmaceutical equivalence;
satisfying FDA extended-release product requirements; and
avoiding other formulation or method-of-use patents.

A formulation that avoids the claimed polymer matrix may still face regulatory comparability issues if it must demonstrate equivalent release and exposure to the reference product.

Key Takeaways

US 8,252,332 protects controlled-release gabapentin matrix dosage forms, not gabapentin as a chemical entity.
The central limitations are five-to-12-hour upper-GI release, reduced Cmax or delayed Tmax, and at least 80% of immediate-release AUCinf.
Claims 7 and 23 specifically target 300 mg and 600 mg dosage configurations.
Claims 4 to 6 and 9 to 11 narrow protection to polymer, swellable hydrophilic and diffusion-controlled matrices.
Claims 12 to 17 and 24 create method-of-treatment exposure for pain and neuropathic pain labeling.
The patent is commercially associated with Gralise, an FDA-approved extended-release gabapentin product.
Generic risk depends on the full Orange Book estate, not US 8,252,332 alone.
A Paragraph IV certification can trigger litigation but does not itself establish invalidity or noninfringement.
Biosimilar risk is irrelevant because gabapentin is a small-molecule drug.
The most important technical evidence is comparative Cmax, Tmax, AUCinf, dissolution and upper-GI release data.

FAQs About US Patent 8,252,332

Does US 8,252,332 cover immediate-release gabapentin?

No. The claims require a matrix dosage form with controlled release and specified pharmacokinetic or bioavailability characteristics.

Does changing the polymer avoid the patent?

Not necessarily. The independent claims do not require a specific polymer. A different polymer may remain within the claims if the dosage form produces the required release and pharmacokinetic profile.

Are 300 mg and 600 mg gabapentin tablets specifically protected?

Yes. Claims 3 and 7 to 11 expressly address 300 mg and 600 mg dosage forms, including one 600 mg tablet or two 300 mg tablets.

Can a generic manufacturer omit the neuropathic-pain indication?

A label carve-out may reduce method-of-use exposure, but it would not necessarily avoid the dosage-form claims or other listed patents.

Is Gralise subject to biosimilar competition?

No. Gralise contains gabapentin, a small-molecule active ingredient. Generic competition proceeds through the ANDA pathway, not the biosimilar pathway.

References

U.S. Food and Drug Administration. (2011). Gralise (gabapentin) extended-release tablets, NDA 022544: Approval letter and prescribing information.
U.S. Patent and Trademark Office. (2012). U.S. Patent No. 8,252,332, controlled release dosage forms.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
U.S. Food and Drug Administration. (2018). Abbreviated new drug application submissions: Refuse-to-receive standards.
U.S. Code, Title 35, §§ 154 and 271(e). Patent term and infringement related to abbreviated new drug applications.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2002348828	⤷ Start Trial
Australia	2005267738	⤷ Start Trial
Australia	2006332690	⤷ Start Trial
Canada	2464322	⤷ Start Trial
Canada	2575555	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,252,332

Summary for Patent: 8,252,332