United States Patent 9,265,737: Scope, Claim Coverage, and US Patent Landscape
US Drug Patent 9,265,737 claims a structured amphetamine formulation built from ion-exchange resin “drug-resin” particles arranged into two particle populations with different release timing: (i) immediate release particles and (ii) delayed release particles coated with a pH-triggered or delayed dissolution coating chemistry. The claims also lock in quantitative weight splits, dissolution and in vivo performance parameters, and administration/forms (liquid, chewable, orally disintegrating tablets).
This creates a landscape where (1) the strongest freedom-to-operate (FTO) risk concentrates around mixed immediate + delayed resin particle blends, (2) design-arounds need to break at least one of the claim’s structural or performance constraints (weight fraction, coating identity, release mechanism, dissolution profile, or plasma target windows), and (3) downstream generic/bridging positioning is tied to bioequivalent ranges and exposure metrics.
What does claim 1 actually require (core structural claim)?
Claim 1 sets the central scaffold:
- Drug substance: “amphetamines complexed with ion-exchange resin particles” to form drug-resin particles.
- Two-plurality architecture:
- A first plurality of immediate release drug-resin particles.
- A second plurality of drug-resin particles with a delayed release coating.
- Weight distribution of amphetamine across the two populations:
- 30% to 50% by weight in the immediate release plurality.
- 50% to 70% by weight in the delayed release (coated) plurality.
This architecture is the gating feature for most dependent claims.
Claim 1 coverage matrix (structural)
| Element |
Claim 1 requirement |
Practical implication |
| Active |
“amphetamines” (broad) |
Includes dextro/levo and mixtures unless limited by dependent claims |
| Resin particle carrier |
ion-exchange resin particles |
Risk for any resin complex-based amphetamine prodrug-like system |
| Particle population split |
2 pluralities: immediate + delayed |
Any single-modality resin system (all immediate or all delayed) avoids Claim 1 |
| Weight split |
30-50% immediate; 50-70% delayed |
“Ratio” is material; narrow swaps can miss coverage |
How do dependent claims narrow mechanism, resins, formulations, and performance?
What release mechanism is claimed (triggered pH option)?
Claim 2 makes the delayed release coating a triggered-release coating triggered by pH change.
Claim 3 then defines coating chemistries (examples include typical enteric/acid-dissolving polymers):
- cellulose acetate phthalate
- cellulose acetate trimellitate
- hydroxypropyl methylcellulose phthalate
- polyvinyl acetate phthalate
- carboxymethylethylcellulose
- copolymerized methacrylic acid/methacrylic acid methyl esters
- copolymerized methacrylic acid/acrylic acid ethyl esters
- or mixtures
Why it matters for scope: these coatings narrow the universe from “any delayed coating” to specific polymer families when Claim 2/3 are invoked.
What resin types are explicitly captured?
Claim 4 limits the ion-exchange resin class to strong acidic cation exchange resins selected from:
- polistirex
- polacrilex
- cholestyramine
- polacrilin
- or mixtures
This is not an all-encompassing definition of “all strong acidic cation exchange resins,” because the claim uses “selected from the group consisting of” the listed resins. That language generally forces the resin into one of those enumerated identities (or an allowed mixture of them).
What weight splits are explicitly protected (tight ranges)?
Claim 5 and Claim 6 narrow Claim 1’s 30-50/50-70 band:
- Claim 5: 40%-50% immediate; 50%-60% delayed.
- Claim 6: “about 45%” immediate; “about 55%” delayed.
Claim 19 offers a further exact-ish midpoint:
- about 50% immediate and about 50% delayed.
What dosage forms are explicitly included?
Claim 7 explicitly states the composition can be:
- liquid suspension
- chewable composition
- orally disintegrating tablet.
What stereochemistry split is explicitly covered?
Claim 8 fixes a specific composition:
- 25% levo-amphetamine
- 75% dextro-amphetamine.
Claim 21 recaps:
- mixture of dextro- and levo-amphetamines (or racemic mixture where applicable).
What dose amount is claimed?
Claim 9:
- amphetamine amount of 2–60 mg.
What dissolution profile and in vivo PK performance are claimed (high-value claim hooks)?
These claims create enforceable “functional” requirements that may be difficult to replicate without matching the formulation and process.
Dissolution profile locked to USP conditions (Claim 10)
Claim 10 requires a multi-stage dissolution release pattern in vitro:
- 40%-45% of amphetamines released within the first 45 minutes
- then substantially no release from 45 minutes to 2 hours
- then 2 to 8 hours: release of “substantially all” remaining amphetamines
Assay conditions:
- initial dissolution medium: 0.1 N HCl
- after 2 hours, adjust to pH about 6.8
- apparatus: USP Apparatus 2
This claim is highly diagnostic: it anchors release lag behavior across acid to near-neutral pH shift.
Delayed release completion timing (Claim 11)
Claim 11 requires:
- delayed coating releases “substantially all” of second plurality amphetamines within about 60 minutes after delayed release initiation.
Ethanol exposure effect (Claim 12)
Claim 12 adds a functional gastric/solvent interaction:
- In ethanol presence, a mammal exposed to a reduced amount of amphetamines versus a reference composition without resin particles.
- It also specifies a mixture:
- dextroamphetamine sulfate
- dextroamphetamine saccharate
- amphetamine aspartate
- amphetamine sulfate
This is a specific performance narrative (resin particles mitigate ethanol-related exposure).
Dose equivalence to “reference composition without resin particles” (Claim 13)
Claim 13 sets composition equivalence:
- amphetamines amount equals total amphetamines in one of reference compositions (5, 10, 15, 20, 25, or 30 mg) without resin particles comprising the same salt mixture described in Claim 12.
Plasma concentration profile targets for ADHD patients (Claims 14, 15)
Claims 14 and 15 are the most commercially relevant enforcement hooks because they specify AUC and Cmax windows.
Claim 14: orally disintegrating tablet (30 mg total dose basis)
Target values (with -20% / +25% window) for dextro and levo are specified across multiple AUC intervals:
- AUC0-4 and Cmax
- AUC0-5 and Cmax
- AUC4-12 and Cmax
- AUC5-12 and Cmax
- AUC0-24 and Cmax
The claim also states scaling: for other total doses, AUC/Cmax are “directly proportional” to the 30 mg total dose.
Claim 15: liquid suspension (30 mg total dose basis)
Same structure but different exposure targets:
- AUC0-4, AUC0-5, AUC4-12 values with separate dextro/levo AUC and shared-ish Cmax values per stereochemistry.
Why the dual set matters: different dosage forms (ODT vs suspension) get different claimed PK windows, tightening enforcement and reducing “generic” equivalence opportunities if a competitor selects a different form.
Total amphetamines AUC0-∞ range (Claim 16)
Claim 16 specifies:
- For about 30 mg total dose, in vivo AUC0-∞ for total amphetamines is about 1140 to about 1240.
Bioequivalence confidence-interval constraint (Claim 17)
Claim 17 requires one or more PK parameters (Cmax, AUC intervals listed) have a 90% confidence interval bounds within 90% to 115% of the reference composition values.
This is consistent with typical bioequivalence practice, but it is explicitly tied to the claimed resin particle dual-release architecture.
Food-effect exposure in first 4 hours (Claim 18)
Claim 18 adds:
- When taken “substantially contemporaneously with food,” patients are exposed to an “increased amount of amphetamines in the first 4 hours” compared to a reference mixture (same salts) without resin particles.
Fasted serum profile with two peaks (Claim 20)
Claim 20 requires:
- fasted profile with a first peak at 1-3 hours,
- second peak at 4-7 hours (and the Cmax is the second peak).
What is the likely “real-world” claim map for competitors?
Most direct overlap: resin dual-population systems
The following design features likely land squarely inside the independent claim scaffold:
- Amphetamine complexed with ion-exchange resin
- Two populations with a controlled immediate fraction and a coated delayed fraction
- Weight ratios within 30-50/50-70
- Delayed coating that is pH-triggered and/or uses pH-sensitive polymer families
- Release behavior that matches the acid to near-neutral shift dissolution curve and/or PK targets
Key claim-break levers for design-around
A competitor can try to avoid coverage by changing one of these claim-critical axes:
- Break the two-plurality design: use a single plurality or a different particle architecture.
- Move the amphetamine weight split outside 30-50/50-70 (or outside dependent tighter ranges like 40-50/50-60, about 45/55, about 50/50).
- Change the delayed release coating chemistry to avoid Claim 2/3 enumerations, or remove pH-triggering.
- Change the resin identity to avoid Claim 4’s enumerated resins (if Claim 4 is asserted).
- Change the release profile away from Claim 10’s USP 0.1 N HCl to pH 6.8 pattern.
- Change dosage form-specific PK windows (ODT vs suspension) to miss Claims 14/15.
- Avoid ethanol-related exposure reduction and the specific salt mixture context if Claim 12 is asserted.
What is the US patent landscape around 9,265,737 (where risk clusters)?
A complete US landscape requires a full bibliographic and citation pull across assignee, continuation family, and all citing/cited documents. That is not possible from the claim text alone.
But the claim set signals where the closest prior art and later patents will cluster:
- Resin complexation of basic drugs: ion-exchange resins complexed with APIs to modulate release and/or reduce extraction in GI fluids.
- Multiparticulate controlled release: blends of immediate and delayed release units in a single dosage form.
- pH-sensitive enteric coatings: cellulose phthalate, hydroxypropyl methylcellulose phthalate, polymethacrylate/methacrylic acid copolymers, and related polymers.
- Amphetamine XR formulations: later patents and formulations commonly benchmark against controlled-release dextro/levo exposure profiles in ADHD dosing and food-effect.
In enforcement, the claim language that matters for landscape mapping is:
- Resin chemistry constraints (Claim 4 enumerations)
- Coating chemistry constraints (Claim 3 enumerations)
- Release kinetics constraints (Claim 10, Claim 11)
- Exposure and dose-form-specific PK targets (Claim 14, Claim 15, Claim 16, Claim 20)
- Bioequivalence statistical constraint (Claim 17)
- Ethanol behavior (Claim 12)
Those hooks narrow the relevant prior art and define the “innovation space” that examiners and litigators focus on.
Scope summary: claim-by-claim risk posture
Independent claims (scope anchor)
- Claim 1: broad in actives (“amphetamines”), but rigid in structure (dual immediate/delayed resin particles) and weight split (30-50% vs 50-70%).
- Claims 12, 14, 15, 16, 17, 18, 20 add narrower constraints (salt mixture, dosage forms, PK/dissolution/food-effect profiles).
Dependent claims (narrow enforcement or coverage)
- Mechanism: Claims 2, 3
- Resin identity: Claim 4
- Weight ratios: Claims 5, 6, 19
- Form: Claim 7
- Stereochemistry and dose: Claims 8, 9, 21
- Release kinetics/dissolution: Claims 10, 11
- Salt mixture/ethanol reduction: Claim 12, 13
- ADHD PK targets: Claims 14, 15
- Total AUC range: Claim 16
- Bioequivalence CI window: Claim 17
- Food effect: Claim 18
- Fasted two-peak profile: Claim 20
Key Takeaways
- US 9,265,737 protects a dual-population resin-based amphetamine system with immediate and pH-responsive delayed resin particles and strict amphetamine weight distributions (Claim 1: 30-50% vs 50-70%).
- Coating and resin identities are partially enumerated (Claims 3 and 4), tightening enforceability for specific polymer and resin chemistries.
- The patent includes high-specificity functional claims: USP Apparatus 2 dissolution behavior across 0.1 N HCl to pH 6.8 (Claim 10), and ODT/suspension-specific ADHD PK windows (Claims 14 and 15).
- The most defensible infringement path is likely through reproducing the multiparticulate structure plus matching dissolution/PK performance, not just using ion-exchange resin with amphetamines.
- For design-around, shifting any one of the claim-critical anchors (architecture, weight split, coating/resin identity, dissolution lag kinetics, or dose-form-specific PK targets) is the most direct way to fall outside claim scope.
FAQs
1) Does 9,265,737 require both immediate and delayed resin particle populations?
Yes. The claim structure requires two pluralities: a first immediate release plurality and a second delayed release coated plurality, with a specified weight split (Claim 1).
2) Are pH-triggered coatings required?
Not in Claim 1. Claim 2 adds pH-triggered triggered-release as a limitation. Claim 3 then narrows acceptable polymer chemistries.
3) Can a different resin than polistirex/polacrilex/cholestyramine/polacrilin avoid the patent?
It can avoid coverage tied specifically to Claim 4 if that dependent claim is asserted, because Claim 4 uses an explicit “selected from” list.
4) What experimental tests are explicitly locked in?
Claim 10 locks in a USP Apparatus 2 dissolution method with 0.1 N HCl followed by pH 6.8 after 2 hours, and a multi-stage release curve. Claim 15/14 lock in specific ADHD human PK AUC and Cmax windows for 30 mg doses.
5) Are the PK targets the same for all dosage forms?
No. Claim 14 targets an orally disintegrating tablet PK profile and Claim 15 targets a liquid suspension PK profile, with different AUC/Cmax values.
References
[1] US Patent 9,265,737. United States Patent and Trademark Office (USPTO).
