United States Patent 7,431,944: Claim Scope, Exclusivity, and Methylphenidate Patent Landscape

U.S. Patent No. 7,431,944 protects a multiparticulate, bimodal-release dosage form containing d-threo methylphenidate or its salt. The independent claim requires two particle populations: an immediate-release population and coated particles containing an ammonio methacrylate copolymer. The formulation must produce two plasma-concentration peaks separated by approximately two to seven hours. Claim 6 adds a pharmacokinetic limitation requiring the two peaks to differ in magnitude by no more than approximately 30%.

The patent is directed to formulation architecture and pharmacokinetic performance, not to d-threo methylphenidate as a molecule. Its commercial relevance depends on whether an accused product uses the required two-particle system, the specified polymer coating, and the claimed bimodal plasma profile.

What does U.S. Patent 7,431,944 protect?

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

Claim element	Requirement
Active ingredient	d-threo methylphenidate or a salt
Dosage form	Solid dosage form
Pharmacokinetics	Two plasma concentration maxima
Peak separation	Approximately two to seven hours
First particle group	About 2% to 99% d-threo methylphenidate or salt
Second particle group	Coated particles
Second-group drug loading	About 2% to 75% d-threo methylphenidate or salt
Binder	One or more binders in the coated-particle core
Coating	Ammonio methacrylate copolymer
Optional dosage forms	Tablet or capsule
Preferred salt	d-threo methylphenidate hydrochloride
Immediate-release limitation	First particle group provides a substantially immediate dose
Peak-balance limitation	Peaks differ by no more than about 30% under claim 6

The central inventive combination is the integration of immediate-release particles with delayed-release, polymer-coated particles in the same dosage form. The claim does not cover every extended-release methylphenidate product. A product that uses a single matrix, osmotic system, ion-exchange resin, or a different coating technology may fall outside the literal scope of claim 1.

How should claim 1 be construed?

Claim 1 is an open “comprising” claim. A product may contain additional excipients, particle populations, coatings, release modifiers, or manufacturing steps and still satisfy the claim, provided all expressly required elements are present.

“Two maxima temporally separated by from about two hours to about seven hours”

This is both a formulation limitation and a performance limitation. The dosage form must generate two identifiable plasma-concentration maxima, with the maxima separated by approximately two to seven hours.

The limitation creates several potential infringement issues:

The parties may dispute how a “maximum” is identified in a concentration-time curve.
A product may produce a shoulder rather than two distinct peaks.
The relevant separation may depend on the study population, fed or fasted state, sampling schedule, and pharmacokinetic model.
“About” introduces tolerance around the two-hour and seven-hour boundaries, but the claim does not establish a fixed numerical margin.

A generic or follow-on manufacturer could challenge this limitation by showing that its product produces a single broad peak, an insufficiently separated shoulder, or a separation outside the claimed interval.

“First group of particles”

The first group must contain approximately 2% to 99% by weight of d-threo methylphenidate or salt. Claim 5 narrows this group by requiring a substantially immediate dose after ingestion.

Claim 1 itself does not expressly require that the first group be uncoated. A formulation could therefore raise a construction dispute if the immediate-release function is achieved through a different particle design. Claim 5 makes the immediate-release role explicit and is narrower.

“Second group of particles”

The second group must be coated particles. The particle core must contain approximately 2% to 75% by weight of d-threo methylphenidate or salt in admixture with one or more binders.

The claim does not specify:

a particular particle size;
a particular coating thickness;
a particular ratio of ammonio methacrylate copolymer to drug;
a particular release rate;
a particular binder;
a particular tablet compression force;
a particular capsule fill weight; or
a particular commercial dose.

Those omissions broaden the structural scope but create proof issues. An infringement analysis would require formulation records, polymer identification, drug-loading data, microscopy or particle characterization, and pharmacokinetic testing.

What do claims 2 through 6 add?

Claims 2 through 6 are dependent claims and narrow claim 1.

Claim	Added limitation	Commercial significance
2	Tablet	Covers compressed solid dosage forms
3	Capsule	Covers capsule dosage forms
4	d-threo methylphenidate hydrochloride	Narrows the active ingredient to the hydrochloride salt
5	First particle group provides substantially immediate dose	Links the first population to immediate release
6	Peak magnitudes differ by no more than about 30%	Requires relatively balanced plasma peaks

Claims 2 and 3 are alternative dosage-form limitations. A capsule product may infringe claim 3 even if it does not infringe claim 2. Claim 4 is important for products using dexmethylphenidate hydrochloride, the active salt commonly associated with Focalin products.

Claim 6 is materially narrower than claim 1. A product could meet the two-peak and particle limitations of claim 1 while avoiding claim 6 if one peak is substantially larger than the other. Conversely, a product that demonstrates balanced peaks but fails the two-to-seven-hour separation requirement would not satisfy claim 6 because it would already fail claim 1.

What formulation technologies are covered?

The patent is strongest against products that combine the following design choices:

dexmethylphenidate hydrochloride;
an immediate-release particle fraction;
a delayed-release particle fraction;
binder-containing drug cores;
ammonio methacrylate copolymer coatings; and
a bimodal pharmacokinetic profile.

Ammonio methacrylate copolymers include pharmaceutical coating materials commonly used to control release, such as polymers in the Eudragit family. The claim language does not require a particular brand or grade. The relevant question is whether the coating material falls within the proper chemical meaning of “ammonio methacrylate copolymer.”

A product using a polymer with a different chemical identity may avoid literal infringement. The doctrine of equivalents could still be asserted, but prosecution history, claim scope, polymer functionality, and prior-art distinctions would control that analysis.

Manufacturing and process barriers

The patent does not expressly claim a manufacturing process. It therefore does not directly prevent a competitor from using a different method to manufacture an equivalent particle population. Its manufacturing relevance is indirect: the required product structure may be difficult to produce consistently at commercial scale.

Potential process controls include:

drug loading in the coated-particle core;
uniformity of the polymer coating;
coating integrity during tablet compression;
segregation between immediate- and delayed-release particles;
dissolution performance;
stability of the coating during storage; and
preservation of the two-peak pharmacokinetic profile.

A competitor may avoid the patent through a different release architecture, but the alternative must still meet FDA performance and bioequivalence requirements.

What is the Orange Book status of U.S. Patent 7,431,944?

A patent number alone does not establish Orange Book listing. FDA Orange Book status must be determined from the current product-specific patent and exclusivity listings for the relevant approved product.

For methylphenidate products, Orange Book relevance depends on the approved product, sponsor, dosage form, strength, and labeling. A patent may be:

listed for one approved product but not another;
listed for tablets but not capsules;
listed against a particular new drug application;
removed, expired, or delisted; or
legally relevant without being listed in the Orange Book.

The patent’s claims are formulation claims and could qualify as a product, formulation, or method-of-use patent for Orange Book purposes if they meet FDA listing requirements and are tied to an approved product. The claims supplied here do not identify the associated NDA or confirm a current Orange Book listing. [1]

When does U.S. Patent 7,431,944 lose exclusivity?

U.S. patent expiration is generally determined by the later of 20 years from the earliest effective nonprovisional filing date in the relevant chain or the applicable pre-URAA rule, subject to patent-term adjustment, patent-term extension, terminal disclaimers, and other statutory provisions. The issue date, October 7, 2008, does not determine the expiration date. [2]

The patent’s enforceability analysis must account for:

Term issue	Relevance
Earliest effective filing date	Establishes the base 20-year term
Continuation or divisional status	May preserve an earlier priority date
Patent-term adjustment	Can extend the base term for USPTO delay
Patent-term extension	May apply if statutory FDA criteria are met
Terminal disclaimer	May cut the term short based on another patent
Maintenance fees	Nonpayment can cause expiration before the nominal term
Litigation status	A court judgment may affect enforceability or validity

Patent expiration does not automatically eliminate FDA regulatory exclusivity. A product may retain remaining NCE, pediatric, orphan, or other FDA exclusivity after patent expiration, although those categories are generally less central for an older methylphenidate formulation patent. [1]

What Paragraph IV challenges could target this patent?

An ANDA applicant could file a Paragraph IV certification if the patent is listed for the reference product and the applicant asserts that the patent is invalid, unenforceable, or not infringed. The likely challenge theories would be:

Noninfringement

A challenger could design around one required limitation, such as:

using a non-ammonio-methacrylate coating;
using a matrix tablet rather than coated particles;
eliminating the immediate-release particle group;
producing a single peak rather than two maxima;
selecting a peak separation outside the claimed range; or
using a formulation that does not contain the claimed drug-loading ranges.

Invalidity

Potential validity attacks would focus on:

anticipation by earlier bimodal methylphenidate formulations;
obviousness based on immediate-release and delayed-release particle systems;
prior use of ammonio methacrylate copolymers in modified-release products;
lack of written description for the full numerical ranges;
enablement of the full combination of particle compositions and pharmacokinetic outcomes; and
indefiniteness involving “about,” “substantially immediate,” and “maxima.”

The pharmacokinetic limitation may provide a defense against purely structural prior art, but it can also create invalidity issues if the claimed profile is viewed as an inherent result of routine formulation optimization.

Which companies are most relevant to the competitive landscape?

The commercially relevant companies are those marketing dexmethylphenidate or other bimodal-release methylphenidate products, including Novartis and generic manufacturers. Focalin XR is a leading reference product for extended-release dexmethylphenidate. Ritalin LA and Metadate CD are competing modified-release methylphenidate products, although their active ingredients, release technologies, and patent estates must be analyzed separately.

Product category	Active ingredient	Typical release concept	Relevance to Patent 7,431,944
Immediate-release dexmethylphenidate	d-threo methylphenidate	Immediate release	Generally outside claim 1 without the second coated-particle group
Extended-release dexmethylphenidate	d-threo methylphenidate	Often multiparticulate or modified release	Potentially relevant
Bimodal methylphenidate	Methylphenidate, formulation dependent	Immediate plus delayed release	Relevant only if active ingredient and polymer limitations are met
Osmotic methylphenidate	Methylphenidate	Osmotic delivery	Usually a different patent category
Matrix methylphenidate	Methylphenidate	Hydrophilic or hydrophobic matrix	Usually outside the literal particle-coating limitation

A competing product cannot be assessed solely by its trade name or by the fact that it produces extended release. The decisive issues are the active enantiomer, particle architecture, coating chemistry, and pharmacokinetic profile.

How strong is the patent estate?

The patent is structurally focused rather than molecule-wide. Its practical strength can be characterized as follows:

Factor	Assessment
Molecular coverage	Narrow; limited to d-threo methylphenidate or salts
Dosage-form coverage	Broad within solid tablets and capsules
Release architecture	Strongly focused on two particle groups
Polymer limitation	Potentially narrowing and design-around sensitive
Pharmacokinetic limitation	Useful for distinguishing single-peak products, but difficult to prove
Salt coverage	Broad in claim 1; hydrochloride specifically covered by claim 4
Manufacturing coverage	Limited because no process claim is supplied
Litigation leverage	Dependent on Orange Book listing, term, and product evidence
Generic design-around risk	Meaningful

The strongest enforcement position would arise against a product that copies the same immediate-release plus coated-particle architecture and uses an ammonio methacrylate copolymer. The weakest position would arise against a product that uses a different delivery system or cannot be shown to produce two distinct maxima.

What generic launch scenarios exist?

A generic applicant could pursue several strategies:

Direct challenge: Replicate the reference product and file Paragraph IV certifications against listed patents.
Formulation design-around: Use a different polymer, matrix, osmotic system, or multiparticulate coating.
Narrow label strategy: Exclude patented method-of-use language if the relevant patent is a method-of-use patent rather than a formulation patent.
Post-expiration launch: Wait for patent expiration and rely on an ANDA without challenging the patent.
Risk-adjusted launch: Launch after receiving tentative approval if the patent is expired, delisted, invalidated, or otherwise unenforceable.

For this patent, the most credible design-around is a non-ammonio-methacrylate controlled-release system that avoids the claimed coated-particle limitation. A formulation that retains the same two-peak profile but changes the release mechanism may still avoid literal infringement.

What patent litigation and settlement issues matter?

The relevant litigation questions are:

whether the patent was listed for a specific NDA;
whether an ANDA applicant served a Paragraph IV notice;
whether a 30-month stay was triggered;
whether the patent was asserted in district court;
whether the parties entered a licensed or delayed-entry settlement;
whether the patent was held valid, infringed, and enforceable; and
whether any settlement included authorized-generic or supply provisions.

No litigation or settlement conclusion follows from the claim text alone. Patent litigation must be tied to the patent’s prosecution history, Orange Book listing, ANDA notices, docket records, and settlement filings.

Key Takeaways

U.S. Patent 7,431,944 targets a bimodal solid dosage form for d-threo methylphenidate.
Claim 1 requires both immediate-release and coated delayed-release particle populations.
The delayed-release particles must contain d-threo methylphenidate or salt, a binder, and an ammonio methacrylate copolymer coating.
The formulation must produce two plasma maxima separated by approximately two to seven hours.
Claim 6 requires the two maxima to be within approximately 30% of each other in magnitude.
The patent does not cover all extended-release methylphenidate products.
The principal design-around options involve changing the coating polymer, release architecture, particle structure, or resulting pharmacokinetic profile.
Orange Book listing, patent-term adjustment, terminal disclaimers, maintenance-fee status, and litigation records determine current commercial enforceability.
The patent’s strength is highest against products that copy the same multiparticulate architecture and polymer chemistry.
Its scope is materially narrower than a molecule patent and vulnerable to formulation-based design-arounds.

FAQs

Does U.S. Patent 7,431,944 cover Focalin XR?

Potential coverage depends on Focalin XR’s actual formulation, the relevant product patent listings, and whether the product satisfies every limitation of claim 1. The trade name alone does not establish infringement.

Does the patent cover racemic methylphenidate?

The claims expressly recite d-threo methylphenidate or its salt. A product containing racemic methylphenidate would require separate analysis and would not automatically satisfy the d-threo limitation.

Can a product infringe without producing two plasma peaks in every patient?

A pharmacokinetic claim generally requires analysis of the claimed profile under the relevant testing conditions. Variability among patients does not by itself resolve infringement. The clinical study design and claim construction would be central.

Are Eudragit-coated particles automatically covered?

No. The relevant question is whether the particular Eudragit material is an ammonio methacrylate copolymer and whether all other claim limitations are met, including particle composition and the two-peak profile.

Does patent expiration permit immediate generic substitution?

Not necessarily. FDA approval status, Orange Book exclusivity, state substitution rules, controlled-substance requirements, and any other unexpired patents or regulatory protections may affect substitution and launch timing.

References

U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA.
United States Patent and Trademark Office. (2024). Patent term adjustment and patent term extension provisions. USPTO.
United States Patent and Trademark Office. (2008). U.S. Patent No. 7,431,944, solid dosage forms comprising d-threo methylphenidate. USPTO.
U.S. Food and Drug Administration. (2024). Orange Book patent and exclusivity information. FDA.
U.S. Code, 35 U.S.C. §§ 154, 156, and 271. (2024). Patent term and infringement provisions.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	306266	⤷ Start Trial
Austria	368458	⤷ Start Trial
Australia	2002318302	⤷ Start Trial
Australia	738521	⤷ Start Trial
Australia	738744	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,431,944

Summary for Patent: 7,431,944