Scope and claims of US Patent 6,635,284 and the US patent landscape for once-daily, dual-release d-threo-methylphenidate (ammonio methacrylate copolymer, 2–7 hour delay)

US 6,635,284 is a late-generation US formulation and method-of-treatment patent focused on once-daily oral dosing of d-threo-methylphenidate (and, by claim dependency, other “phenidate” methylphenidate salts) using a dual-population particle system. The core technical claim element is a two-part dose: an immediate fraction and a delayed fraction where the delayed fraction uses an ammonio methacrylate copolymer coating to produce a 2–7 hour delay (and “two maxima” in plasma with separation of 2–7 hours and with no more than ~30% difference in maxima magnitude). In practice, this maps to the drug’s clinical goal of smoothing early and later exposure from a single once-daily oral product.

What does US Patent 6,635,284 claim for once-daily d-threo-methylphenidate dual-release formulations?

Bottom line: The patent claims a specific delayed-release mechanism (ammonio methacrylate copolymer coating) combined with defined time windows (2 to 7 hours delay; 2 to 7 hours separation between plasma maxima) and particle-population constraints (two groups of particles with defined wt% ranges of active/salt and binder/admixture ranges for the delayed fraction).

Claim 1: Method-of-treatment using two particle groups and an ammonio methacrylate copolymer delayed fraction

Independent claim 1 is a method claim that requires all of the following, cumulatively:

Indication scope language: “A method for treating disease amenable to treatment with a phenidate drug…”
- This is intentionally broad on disease/indication; it anchors infringement to any disease category where a methylphenidate (“phenidate”) is used.
Once-daily oral administration of d-threo-methylphenidate hydrochloride.
Dosage form composition: two groups of particles, each containing d-threo-methylphenidate, with:
- First group (immediate): 2% to 99% by weight of d-threo-methylphenidate hydrochloride, providing a “substantially immediate dose upon ingestion.”
- Second group (delayed): “coated particles,” comprising:
  - 2% to 75% by weight of d-threo-methylphenidate in admixture with one or more binders, and
  - a coating consisting of an ammonio methacrylate copolymer, at an amount sufficient to delay drug by 2 to 7 hours following ingestion.

Key claim scope levers

Time window: 2–7 hours delay is a hard claim constraint.
Coating material identity: “ammonio methacrylate copolymer” is the formulation chemistry gate.
Two-pulse / dual-exposure behavior is not explicitly required in claim 1, but it is functionally created by the particle system and reinforced via claims 2 and 10–11.

Claim 2: Dosage form defined by in vivo plasma profile (two maxima with bounded magnitude difference)

Claim 2 defines a dosage form of a pharmaceutically acceptable methylphenidate salt with an in vivo plasma concentration-time curve having:

Two maxima separated by 2 to 7 hours, and
Magnitude difference between the maxima of no more than 30%.

This claim effectively ties infringement to exposure matching parameters. It is broader on particle description (compared with claim 1) because it uses a pharmacokinetic phenotype rather than specifying the exact microstructure.

Claim 3: Parallel method claim for “phenidate drug” (not limited to d-threo-methylphenidate hydrochloride)

Claim 3 tracks claim 1 but replaces:

fixed “d-threo-methylphenidate hydrochloride” with a broader “phenidate drug” framing.

It still requires:

once-daily oral administration,
two particle groups,
first group immediate (2–99 wt% active),
second group coated particles with ammonio methacrylate copolymer and 2–7 hour delay,
delayed fraction composed of active (2–75 wt%), binders, and ammonio methacrylate copolymer coating.

Claims 4–9: Delay and maxima separation floors (at least 3 hours, at least 4 hours)

These are narrower dependent formulations of claims 1–3 and 2:

Claim 4 / 6: delay is at least 3 hours; at least 4 hours respectively.
Claim 5 / 7: further tighten delay.
Claim 8 / 9: plasma maxima separation is at least 3 hours; at least 4 hours respectively.

Practical implication: These dependent claims create litigation leverage for “near-miss” products that land in the 2–3 hour region. A product with delay consistently below a threshold can avoid these narrower dependent claims but still remain exposed to broader 2–7 hour claims.

Claims 10–11: Release profile defined by two pulses (in vitro) and two maxima with bounded magnitude difference (in vivo)

Claim 10: method claim requiring an in vitro release profile comprising two pulses separated by 2 to 7 hours for a dosage form that is a pharmaceutically acceptable salt of d-threo-methylphenidate.
Claim 11: method claim requiring in vivo plasma concentration comprising two maxima separated by 2 to 7 hours with maxima magnitude difference ≤ 30%.

Claim 10 is an alternate infringement pathway: a party could avoid the “ammonio methacrylate copolymer” language if they can argue that their product does not meet claim 1/3 coating requirements, but still falls within a two-pulse in vitro release behavior that meets the defined time separation.

Claim 11 is the exposure-phenotype counterpart to claim 2 and increases evidentiary focus on pharmacokinetic testing.

What exact technical elements create enforceable infringement risk under US 6,635,284?

1) Does the accused product use a dual population particle system?

The independent claims require two groups of particles (immediate and delayed). This can be satisfied by mixed populations in a capsule/tablet where the delayed fraction is coated granules/beads/spheres.

2) Is the delayed fraction coated with an ammonio methacrylate copolymer?

Claim 1 and 3 use an explicit coating composition limitation:

“a coating consisting of an ammonio methacrylate copolymer.”

If the accused product uses ammonio methacrylate polymers but as part of a blended coating system, the “consisting of” language can become pivotal. “Consisting of” is typically treated as excluding additional coating components beyond the specified polymer (absent some claim interpretation space).

3) Does the system deliver a 2–7 hour delay (or delayed pulse separation)?

The patent hard-codes:

2 to 7 hours delay for claim 1/3, and
2 to 7 hours separation for plasma maxima (claims 2/8/9/11) and release pulses (claim 10).

4) Does the formulation meet the active wt% ranges in each particle population?

Claim 1/3 require:

First group: 2%–99% by weight active (d-threo-methylphenidate HCl / phenidate drug, depending on the claim).
Second group: 2%–75% by weight active in admixture with binders.

These ranges can be decisive for generic design-around efforts that change loading, particle mass fractions, or binder ratios.

5) Does the plasma maxima phenotype meet the “≤30% difference” cap?

The “magnitude differ by no more than about 30%” requirement is a specific pharmacokinetic constraint. It can narrow infringement for products with more pronounced “peaky” early exposure or later exposure.

How does US 6,635,284 compare with other methylphenidate extended-release patent strategies (immediate+delayed vs osmotic vs matrix)?

Featured design archetypes in methylphenidate extended-release

Bead/granule coated immediate + delayed (multi-unit pellet systems): closely aligned with the two-group particle concept.
Hydrophilic matrix or ER microsystems: may create delayed release without a distinct two maxima separation, or with different coating polymers.
Osmotic pump systems: typically rely on membrane/pressure mechanisms, not ammonio methacrylate copolymer coatings.
Single coating with internal gradation: can produce broader tails rather than two pulses or two distinct maxima.

Patent 6,635,284 is positioned to cover the multi-population, coated-particles strategy with a specific polymer type and defined time separation and maxima constraints.

What does this patent’s claim set imply for generic and biosimilar entry risk?

Biosimilar risk: Not applicable. Methylphenidate is a small molecule; “biosimilar” does not apply.

Generic risk: High on formulation engineering if the generic:

uses a dual immediate + delayed particle population,
uses an ammonio methacrylate copolymer delayed coating,
and reproduces the 2–7 hour delay/pulse separation and (for the stronger pharmacokinetic claims) the two-maxima phenotype with ≤30% magnitude difference.

Design-around levers:

Change coating polymer away from ammonio methacrylate copolymer (or use coating systems that avoid the “consisting of” requirement).
Alter the exposure profile so that either:
- the second peak separation falls outside 2–7 hours, or
- the peaks differ by more than ~30%.
Remove the two-pulse in vitro signature and/or shift from a clearly bimodal release profile to a more monotonic or differently distributed release curve.

What Orange Book status is expected for US 6,635,284 and which listed products are most likely implicated?

Exact Orange Book listing and FDA product tie-in are not stated in the provided text, and no definitive Orange Book mapping can be produced from the patent claims alone.

What can be stated from the claim language:

The patent is tightly aligned to extended-release, once-daily oral methylphenidate products built around a dual-release profile.
The claims are drafted for d-threo-methylphenidate salts with a bimodal exposure goal.

Products most likely in the same commercial neighborhood are the established once-daily extended-release methylphenidate lineages (including systems commonly built around multi-unit pellets and coated delayed fractions). However, without Orange Book listings and FDA approval mapping in the record provided here, a precise “Orange Book status” cannot be asserted.

What is the practical scope of enforceability: method-of-treatment vs dosage-form patents under US 6,635,284?

Method claims (claims 1, 3, 4–7, 10, 11)

Method claims require performance of the claimed steps in the US:

prescribing/administering once-daily oral d-threo-methylphenidate ER with the specified dosage form behavior.

For generic manufacturers, method claims can be a secondary route of infringement depending on how the product is introduced, labeled, and administered.

Dosage-form claim (claim 2)

Dosage-form claim is a direct product claim:

“providing an in vivo plasma concentration … two maxima” with defined separation and magnitude difference.

This is typically enforced against the product itself via formulation and performance tests.

Claim-by-claim enforceability map (what must be proven)

Claim	Claim type	Required technical proof elements (infringement checklist)
1	Method (d-threo-methylphenidate HCl)	Once-daily oral; two particle groups; first group immediate; second group coated particles; delayed fraction uses ammonio methacrylate copolymer coating; delay 2–7 hours; wt% ranges for first and second populations
2	Dosage form	In vivo plasma concentration profile: two maxima separated 2–7 hours; maxima magnitude difference ≤30%
3	Method (“phenidate drug”)	Same dual particle + ammonio methacrylate coating + delay 2–7 hours structure, generalized to other phenidate drugs/salts
4–7	Dependent method	Delay threshold at least 3 hours (claims 4,6) and at least 4 hours (claims 5,7)
8–9	Dependent dosage form	Plasma maxima separation threshold at least 3 hours (claim 8) and at least 4 hours (claim 9)
10	Method (in vitro release)	Dosage form of d-threo-methylphenidate salt; in vitro release has two pulses separated 2–7 hours
11	Method (in vivo exposure)	In vivo plasma profile has two maxima separated 2–7 hours; maxima magnitude difference ≤30%

How strong is the patent estate around this concept, based on this patent’s claim architecture?

Strength features of US 6,635,284

Multi-parameter claim structure: composition (ammonio methacrylate copolymer), architecture (two particle groups), performance timing (2–7 hours), and exposure phenotype (two maxima and ≤30% magnitude difference).
Redundant performance hooks: even if composition is debated, claim 10 (in vitro two-pulse) and claim 2/11 (in vivo two-maxima with bounded magnitude) provide alternate proof routes.

Vulnerability features

Coating language is narrow: “coating consisting of an ammonio methacrylate copolymer” can permit straightforward avoidance by changing polymer identity or using coating formulations argued to fall outside “consisting of.”
Performance windows invite “tuning”: generic products can be engineered to shift delays outside 2–7 hours or to produce a second peak separation or relative maxima magnitude that misses the ≤30% requirement.

Without the rest of the family (continuations/divisionals) and the prosecution history, the claim architecture suggests meaningful enforceability against products that copy the same polymer and bimodal timing, and lower leverage against products that diverge in polymer and pharmacokinetic shape.

Key Takeaways

US 6,635,284 is centered on once-daily oral d-threo-methylphenidate (and phenidate variants) using a two-population particle system: immediate fraction plus ammonio methacrylate copolymer-coated delayed fraction.
The patent locks in timing (delay/pulse separation 2–7 hours) and, for several claims, a pharmacokinetic phenotype (two plasma maxima separated 2–7 hours with maxima magnitude difference ≤30%).
Enforceability is supported by multiple proof pathways: dosing architecture + coating identity (claims 1/3), plasma phenotype (claims 2/11), and in vitro two-pulse behavior (claim 10).
Design-around is most feasible by altering the polymer system away from ammonio methacrylate copolymer (especially given “consisting of”) and by changing the bimodal timing and relative peak magnitude so the 2–7 hour and ≤30% constraints are missed.

FAQs

Can a product with a single broadened release profile avoid the “two maxima” claims of US 6,635,284?
How do dependent claims with “at least 3 hours” and “at least 4 hours” delay thresholds affect infringement exposure near the 2–3 hour region?
If a generic uses ammonio methacrylate copolymer but blends it with other coating polymers, does “coating consisting of” change infringement risk?
What tests typically establish compliance with “two pulses” in vitro and “two maxima” in vivo for methylphenidate ER products?
Which elements are most actionable for freedom-to-operate review for an ER methylphenidate dossier targeting once-daily dosing?

References

No external sources were cited because the prompt provided only the claims text and did not include patent bibliographic data, family members, prosecution history, FDA/Orange Book listings, or litigation records needed for verifiable cross-references.

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
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,635,284

Summary for Patent: 6,635,284