US Patent 8,987,333: Amantadine Osmotic-Release Patent Scope and Competitive Landscape

US Patent 8,987,333 protects an amantadine osmotic-delivery device that combines a semipermeable, orifice-containing core with an immediate-release amantadine overcoat. The claims require both structural elements and pharmacokinetic performance: at least 50% of the drug must be in the core, total drug content must be 50 mg to 500 mg, and the device must materially reduce the early plasma-concentration slope compared with an immediate-release product. The patent is directed to controlled-release amantadine products, including formulations competing with Osmolex ER and other extended-release amantadine products.[1][2]

The estate is commercially important because the claims do not rely solely on an osmotic mechanism. A competing product must also satisfy specified dose-distribution and human pharmacokinetic limitations. Those limitations create formulation-development and Paragraph IV certification risks, although they also create infringement and validity questions involving testing methodology, claim construction, enablement, and reproducibility.

What does US Patent 8,987,333 protect?

The patent protects a dosage form with the following required elements:

Claim element	Required scope
Device architecture	Core surrounded by a semipermeable membrane
Drug-release feature	Exit means through the membrane
Active ingredient	Amantadine or a pharmaceutically acceptable salt
Core composition	Drug, osmotically active component, and at least one other excipient
External layer	Immediate-release overcoat containing amantadine
Total drug load	50 mg to 500 mg
Core drug allocation	At least 50% of total drug in the core
Release performance	Reduced mean dC/dT versus an equivalent immediate-release dose
Pharmacokinetic comparison	Single-dose human study
Optional performance limitation	Maintained bioavailability
Tmax limitation	A 2-hour to 16-hour shift relative to immediate-release amantadine

The independent claims are formulation-device claims. They are not claims to amantadine itself, a general method of treating Parkinson's disease, or a generic sustained-release tablet without the claimed osmotic and overcoat architecture.

How do claims 1 through 3 differ?

Claims 1 through 3 cover substantially the same device but use different pharmacokinetic observation windows.

Claim	Osmotic-device dC/dT measurement	Immediate-release comparator
Claim 1	0 to 4 hours after administration	Same 0-to-4-hour period
Claim 2	Administration to Tmax of immediate-release product	Same comparator period
Claim 3	2 to 4 hours after administration	Administration to immediate-release Tmax

Claim 3 is potentially significant for infringement analysis because it uses nonmatching time windows. The osmotic product is assessed during the 2-to-4-hour interval, while the immediate-release product is assessed from administration through its Tmax. A party challenging the patent could argue that the measurement is methodologically asymmetric or insufficiently reproducible. The patent holder would argue that the claim expressly defines the comparison and that the relevant issue is whether the claimed product produces the specified reduction under the stated protocol.

Claims 1 to 3 each require dC/dT below 40% of the immediate-release comparator. Dependent claim 8 broadens the permitted threshold to less than 50%, while dependent claim 9 repeats the less-than-40% limitation.

What formulation features are protected?

Osmotic core

The core must contain:

Amantadine or an acceptable salt;
An osmotically active component; and
At least one other excipient.

The claim does not require a particular osmogen, polymer, binder, lubricant, coating thickness, membrane material, or orifice geometry. That language creates broad literal coverage across different excipient selections, provided the finished dosage form satisfies the structural and pharmacokinetic limitations.

The absence of expressly named excipients also shifts the dispute toward claim construction and testing. A generic manufacturer may avoid particular embodiments disclosed in the specification while still falling within the claims if its product has the claimed core, membrane, exit means, overcoat, drug allocation, and PK profile.

Semipermeable membrane and exit means

The membrane must be semipermeable and must have an exit means. The claims do not expressly limit the exit means to a laser-drilled hole. A drilled orifice is the conventional implementation, but other openings or release structures could fall within the claim depending on the specification and prosecution history.

The membrane limitation excludes ordinary matrix tablets and many diffusion-controlled capsules unless they also include the claimed osmotic architecture. A matrix formulation that releases amantadine slowly but lacks a semipermeable membrane with an exit means would face a strong noninfringement position.

Immediate-release overcoat

The external overcoat must contain the drug and must provide immediate release. This element is central to the intended release profile. It allows an initial amantadine dose while the osmotic core provides later delivery.

A product with all of the core and membrane elements but no amantadine-containing immediate-release overcoat should fall outside the literal claims. The risk increases if the product uses a rapidly dissolving external drug layer under different terminology, because infringement would turn on the actual function and composition rather than the label used by the manufacturer.

How do the dependent claims narrow the patent?

Dependent claim	Added limitation
Claim 4	Total drug content of 100 mg to 500 mg
Claim 5	Total drug content of 200 mg to 500 mg
Claim 6	At least 75% of drug in the core
Claim 7	At least 90% of drug in the core
Claim 8	dC/dT less than 50% of immediate-release product
Claim 9	dC/dT less than 40% of immediate-release product
Claim 10	Extent of drug bioavailability is maintained
Claim 11	Tmax shift of 2 to 16 hours versus immediate-release amantadine

The dependent claims provide fallback positions if an independent claim is narrowed or invalidated. Claims 5, 7, and 11 are particularly relevant to a product with a 200 mg or higher dose, a heavily core-loaded design, and a substantial Tmax delay.

Claim 10 adds a bioavailability requirement but does not define “maintained” in the text provided. That creates a potential indefiniteness and infringement issue unless the specification supplies a measurable standard, such as comparable AUC or a specified bioequivalence range.

When does US Patent 8,987,333 lose exclusivity?

US Patent 8,987,333 issued on March 24, 2015.[1] Its enforceable term is governed by the earliest effective nonprovisional priority date, the filing history, patent-term adjustment, patent-term extension, terminal disclaimers, and any applicable regulatory extension. The patent should be treated as a live formulation patent through its statutory term unless the USPTO records or a court judgment establish earlier loss of enforceability.

For commercial planning, the relevant date is the patent expiration date shown in the current USPTO Patent Center record and, if listed for an approved product, the FDA Orange Book. Patent issuance date alone does not establish expiration. FDA-listed patent information can also differ from a party's broader patent-estate analysis because the Orange Book covers patents submitted for approved drug products, not every patent potentially relevant to a formulation or manufacturing process.[3][4]

Regulatory exclusivity versus patent exclusivity

Amantadine is an old active ingredient. Its principal competitive barriers arise from formulation patents, FDA approval requirements, and product-specific clinical or bioequivalence testing rather than new-molecular-entity exclusivity.

The relevant commercial distinction is:

Barrier	Relevance to amantadine
NME exclusivity	Generally unavailable for an old active ingredient
Orphan exclusivity	Product- and indication-specific; not inherent to amantadine
NDA approval	Required for an extended-release product
Orange Book patents	Can delay an ANDA through Paragraph IV litigation
Formulation patents	May cover release architecture and PK performance
Manufacturing patents	May restrict membrane, coating, drilling, or process design
Trade secrets	May protect coating parameters and scale-up controls

What is the Orange Book status of this patent?

The FDA Orange Book is the controlling public source for determining whether US Patent 8,987,333 is currently listed against a specific approved amantadine product, the listed use code, and any associated patent-use statement.[3] A patent may be relevant to a product without being listed, and a listed patent may not cover every commercially relevant embodiment.

For an ANDA applicant, the key questions are whether the patent is listed against the reference product, whether the proposed label overlaps the listed use code, and whether the applicant files a Paragraph IV certification. A product-specific Orange Book analysis should distinguish:

Product patents;
Drug-substance patents;
Method-of-use patents;
Device or delivery-system patents;
Manufacturing-process patents; and
Patents that are not eligible for Orange Book listing.

Which products and companies are most relevant?

Osmolex ER

Osmolex ER is an extended-release amantadine hydrochloride product approved by FDA for Parkinson's disease and drug-induced extrapyramidal reactions.[2][5] The product uses an extended-release delivery system and is the most direct commercial comparator for an amantadine osmotic formulation patent.

The commercial relevance of US 8,987,333 depends on whether the patent is listed against Osmolex ER and whether the approved product embodies the claimed membrane, exit means, drug-containing overcoat, core drug allocation, and PK limitations.

Gocovri

Gocovri is an extended-release amantadine capsule developed by Adamas Pharmaceuticals and approved for dyskinesia in patients with Parkinson's disease receiving levodopa-based therapy.[6] Its indication and formulation profile differ from Osmolex ER. Gocovri is associated with a separate Adamas patent estate covering delayed-release and extended-release amantadine products.

The existence of a separate Gocovri estate limits the inference that every extended-release amantadine product infringes US 8,987,333. Patent overlap must be tested claim by claim, particularly against the required osmotic membrane, exit means, and immediate-release overcoat.

Immediate-release amantadine

Immediate-release amantadine hydrochloride products are the comparator products embedded in claims 1 through 3 and 8 through 11. They are not necessarily competing infringing products. Their principal role in the patent is to establish the reference dC/dT and Tmax values used to define the claimed controlled-release performance.

How strong is the patent estate?

The patent has meaningful technical breadth but several litigation-sensitive limitations.

Strengths

The claims combine structure and measured performance.
The core may use a broad range of excipients.
The claims cover both amantadine and pharmaceutically acceptable salts.
The dose range encompasses common commercial strengths.
The immediate-release overcoat distinguishes the invention from many conventional matrix systems.
Dependent claims create multiple fallback positions for core loading, dose, and Tmax shift.

Vulnerabilities

The dC/dT limitation requires human pharmacokinetic testing.
Results may vary with food, subject population, sampling schedule, assay method, and statistical treatment.
Claim 10 uses “maintained” bioavailability without a numerical threshold in the claim text.
The term “exit means” may raise means-plus-function issues under 35 U.S.C. §112(f).
Prior art involving osmotic delivery, amantadine, immediate-release overcoats, and controlled plasma profiles could support obviousness arguments.
The claims may be difficult to enforce against a product whose release profile is similar but whose structure differs.

The patent is strongest against a product that copies the commercial architecture: an amantadine-containing immediate-release outer layer, an osmotic core with most of the drug load, and a measured early dC/dT reduction. It is weaker against a nonosmotic matrix, multiparticulate, delayed-release, or capsule-based design that does not have the claimed membrane-and-exit structure.

What Paragraph IV challenges and litigation risks exist?

An ANDA applicant seeking approval before patent expiration could file a Paragraph IV certification if the patent is listed against the reference product. The applicant would typically assert one or more of the following:

The proposed product lacks an osmotic core;
The product lacks a semipermeable membrane;
There is no claimed exit means;
The immediate-release external layer does not contain amantadine;
Less than 50% of the drug is in the core;
The dC/dT threshold is not met;
The patent is invalid for anticipation or obviousness;
The PK limitations are indefinite or not enabled; or
The listed patent does not properly cover the proposed product or approved use.

A notice letter can trigger a 45-day period for the patent owner to file suit under the Hatch-Waxman framework. A timely action can impose a statutory stay of FDA approval for up to 30 months, subject to statutory exceptions and court developments.[4]

No conclusion about a particular Paragraph IV notice, settlement, or active infringement case follows from the claim text alone. Product-specific litigation status must be determined from FDA listing data and federal court records.

What generic launch scenarios are most plausible?

Scenario	Technical design	Patent risk
Direct osmotic copy	Same membrane, exit means, overcoat, and core loading	High
Osmotic redesign	Different membrane or release mechanism but similar PK	Medium to high
Matrix tablet	Polymer matrix without semipermeable membrane and exit means	Lower under literal claims
Multiparticulate capsule	Coated pellets or beads without a single claimed osmotic core	Lower, subject to equivalents
Delayed-release product	Later release with no immediate-release amantadine overcoat	Potentially lower
Immediate-release generic	No controlled-release architecture	Outside the principal claim scope

The strongest design-around path is a nonosmotic delivery system. A competing osmotic device can reduce risk by changing the drug location, eliminating the amantadine overcoat, using a different release mechanism, or producing a PK profile outside the claimed thresholds. Each change must still satisfy FDA performance and labeling requirements.

Does the patent create a biosimilar risk?

No conventional biosimilar pathway applies. Amantadine is a small-molecule drug, so competitive products would generally proceed through an ANDA, 505(b)(2) application, or, in limited circumstances, a full NDA pathway rather than the Public Health Service Act biosimilar pathway.

The practical substitute for biosimilar risk is generic and 505(b)(2) risk. A 505(b)(2) applicant could rely partly on existing FDA findings while pursuing a modified controlled-release formulation. That pathway may create formulation-patent exposure without requiring the applicant to duplicate every feature of the reference product.

What manufacturing and geographic IP barriers matter?

The patent is a US patent and directly controls US commercial manufacture, importation, use, sale, and offer for sale during its enforceable term. Related foreign applications may protect corresponding formulations in Europe, Canada, Japan, or other markets, but foreign family members require separate validity, prosecution, and expiration analysis.

Manufacturing risk is concentrated in:

Semipermeable membrane composition;
Coating weight and permeability;
Orifice formation;
Core compaction;
Osmogen concentration;
Immediate-release overcoat uniformity;
Drug distribution between overcoat and core; and
Scale-up controls that preserve the claimed PK profile.

A manufacturer may avoid literal infringement by producing a different dosage form, but it can still face process-patent, formulation-patent, trade-secret, or contractual risks. A license covering manufacturing technology would not necessarily eliminate product-patent exposure.

How does US Patent 8,987,333 compare with the broader amantadine landscape?

Issue	US 8,987,333	Gocovri-related estate	Immediate-release amantadine
Main technology	Osmotic core plus IR overcoat	Extended/delayed-release capsule technology	Conventional immediate release
Principal commercial target	Controlled-release amantadine	Parkinson's dyskinesia	Parkinson's disease and other established uses
Key limitation	dC/dT reduction and core drug allocation	Product-specific release profile and formulation claims	No comparable controlled-release limitation
Likely FDA pathway for competitor	ANDA or 505(b)(2)	ANDA or 505(b)(2)	ANDA
Biosimilar pathway	Not applicable	Not applicable	Not applicable
Primary patent risk	Structural and PK combination	Separate formulation and use claims	Usually limited to remaining listed patents

Key Takeaways

US Patent 8,987,333 claims an amantadine osmotic device, not amantadine generally.
The required combination is a semipermeable membrane, exit means, osmotic core, amantadine-containing immediate-release overcoat, and defined drug allocation.
At least 50% of the drug must be in the core, with a total dose of 50 mg to 500 mg.
The device must reduce early amantadine plasma-concentration slope relative to immediate-release amantadine.
Claims 1 through 3 differ mainly in the PK measurement window.
Claims 4 through 11 provide narrower fallback positions for dose, core loading, bioavailability, dC/dT, and Tmax.
Osmolex ER is the most direct commercial product for assessing potential relevance.
Gocovri is a separate commercial and patent competitor with a distinct formulation and indication profile.
Generic risk is highest for a direct osmotic copy and lower for a matrix, multiparticulate, or nonosmotic redesign.
The patent does not create biosimilar exposure because amantadine is a small molecule.
Orange Book listing, current patent term, Paragraph IV activity, and litigation exposure must be evaluated against the specific reference product and current USPTO and FDA records.

FAQs

Is US Patent 8,987,333 a method-of-use patent?

No. The supplied claims are apparatus or dosage-form claims. They require a physical osmotic device and specified formulation and pharmacokinetic characteristics.

Can a matrix tablet infringe US Patent 8,987,333?

A conventional matrix tablet without a semipermeable membrane and exit means should not literally meet the principal structural limitations. Equivalents and other patents remain separate issues.

Does the patent cover amantadine free base and amantadine hydrochloride?

Yes. The claims cover amantadine and pharmaceutically acceptable salts. Amantadine hydrochloride is the principal commercially relevant salt.

Is a 100 mg amantadine product within the claimed dose range?

Yes. Claims 1 through 3 cover 50 mg to 500 mg, and claim 4 specifically covers 100 mg to 500 mg, assuming the remaining structural and PK limitations are met.

Can a competitor avoid the patent by placing all drug in the osmotic core?

That design would satisfy the core-allocation limitation but could still avoid the patent if it lacks the claimed immediate-release amantadine overcoat or fails another required element. It would not avoid other formulation or manufacturing patents.

References

United States Patent and Trademark Office. (2015). US Patent No. 8,987,333, controlled release formulations of amantadine.
U.S. Food and Drug Administration. (2018). Osmolex ER: Amantadine hydrochloride extended-release tablets, prescribing information.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, Orange Book.
U.S. Food and Drug Administration. (n.d.). Hatch-Waxman information and Paragraph IV patent certifications.
U.S. Food and Drug Administration. (2018). Osmolex ER approval materials.
U.S. Food and Drug Administration. (2017). Gocovri: Amantadine extended-release capsules, prescribing information.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Canada	2588296	⤷ Start Trial
European Patent Office	1845968	⤷ Start Trial
European Patent Office	2623099	⤷ Start Trial
World Intellectual Property Organization (WIPO)	2006058236	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,987,333

Summary for Patent: 8,987,333