United States Patent 8,618,087 (Ganaxolone solid stabilized nanoparticles) Scope, Claims, and US Patent Landscape
US Patent 8,618,087 is directed to methods of treating central nervous system (CNS) disorders by administering oral solid stabilized particles that contain ganaxolone formulated as nanometer-scale particles (D50 50 to 500 nm). The claimed formulation is defined by a tight set of physicochemical parameters: a hydrophilic polymer, a wetting agent, and a small-molecule complexing agent (MW < 550) selected by functional moiety categories (phenol, aromatic ester, aromatic acid). The claims also lock in stability under simulated gastric/intestinal fluid (SGF/SIF) and in vivo exposure outcomes (fed vs fasted plasma AUC and Cmax, plus fed/fasted ratios and steady-state Cmax/Cmin).
What is the claim scope at a technical level?
Core claim construct (independent claim 1)
Claim 1 recites a method that requires all of the following:
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Indication (CNS disorder set): treatment of a CNS disorder selected from a long enumerated group, including:
- epileptic seizures, infantile spasms
- anxiety, stress, panic, depression, postpartum depression, insomnia
- premenstrual syndrome, post-traumatic stress disorder
- substance abuse withdrawal
- hypertension, pain, migraine headache, headache associated with pre- and peri-menstrual period
- Niemann Pick disease Type-C; Mucolipidosis Type IV lipid accumulation; Mucolipidosis Type IV lipid accumulation (duplicate in text)
- AIDS-related dementia; Alzheimer’s disease; Huntington’s disease; Parkinson’s disease
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Route/format requirement: administration of solid stabilized particles (claim 1 does not explicitly limit to powder-only, but dependent claim 8 does; dosage forms are then covered in dependents).
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Formulation ingredients and constraints:
- Ganaxolone in the solid stabilized particles
- Hydrophilic polymer (defined broadly in claim 1, then narrowed in dependents)
- Wetting agent
- Complexing agent defined as:
- small organic molecule with molecular weight < 550
- having a moiety selected from:
- phenol moiety or
- aromatic ester moiety or
- aromatic acid moiety
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Particle size and composition constraints:
- Volume weighted median diameter (D50): 50 nm to 500 nm
- Ganaxolone loading: at least 50% by weight
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Additional formulation-stability constraints (via dependents 4-7):
- D50 growth in SGF/SIF at 0.5 to 1 mg ganaxolone/mL, heated 36 to 38°C, 1 hour:
- not more than about 150% increase vs. distilled water reference
- SGF/SIF D50 less than about 750 nm
In other words, the scope is not just “ganaxolone nanoparticles”; it is ganaxolone solid stabilized nanoparticles defined by component classes + narrow nanoparticle size + strong dissolution-media stability + high ganaxolone fraction.
What do dependent claims add (breadth vs. narrowing)?
Composition percentage ranges
- Hydrophilic polymer: 3% to 50% w/w of solid particles (claim 2)
- Wetting agent: 0.01% to 10% w/w (claim 3)
- Ganaxolone amount: >50% to about 80% w/w (claim 6)
- Complexing agent amount: 0.05% to about 5% w/w (claim 43)
Particle dispersion stability in SGF/SIF (hard constraints)
Two dependent claim groupings set the same test concept with different experimental volume details:
- Increase limited to 150%, and SGF/SIF D50 < 750 nm after 1 hour at 36 to 38°C for dispersion at 0.5 to 1 mg/mL (claim 4 and claim 7)
- A second dependent variant explicitly uses 15 mL of SGF/SIF at 0.5 to 1 mg/mL with the same D50 increase ceiling and SGF/SIF D50 < 750 nm (claim 5)
Explicit material form and dosage forms
- Powder format (claim 8)
- Tablets or capsules (claim 9)
- Solid dosage form with additional excipients (claim 18), with subcategories:
- ionic dispersion modulator
- water soluble spacer
- disintegrant
- binder
- surfactant
- plasticizer
- lubricant
Explicit ingredient exemplars (further narrowing of the component sets)
Complexing agent exemplars (claim 11-12 and 44-46):
- Selected from:
- parabens, benzoic acid, methyl anthranilate
- plus pharmaceutically acceptable salts and mixtures
- Paraben selection:
- methylparaben, ethylparaben, propylparaben (claim 12)
- Explicit complexing agent embodiments:
- methylparaben (claim 44)
- benzoic acid (claim 45)
- methyl anthranilate (claim 46)
Hydrophilic polymer exemplars (claim 13-16):
- cellulosic polymer, vinyl polymer (claim 13)
- cellulose ether (claim 14)
- hydroxypropylmethylcellulose (claim 15)
- polyvinyl alcohol (claim 16)
Wetting agent exemplars (claim 17):
- sodium lauryl sulfate
- docusate (pharmaceutically acceptable salt)
- mixtures
Ionic dispersion modulator exemplars and ranges (claims 19-23):
- ionic dispersion modulator amount: 1% to 50% w/w (claim 20)
- modulator can be:
- a salt (claim 21)
- inorganic salt: magnesium, calcium, lithium, potassium, sodium (claim 22)
- organic salt: citrate, succinate, fumarate, malate, maleate, tartrate, glutarate, lactate (claim 23)
Water soluble spacer exemplars (claims 24-27):
- 2% to 60% w/w (claim 25)
- saccharide or ammonium salt (claim 26)
- saccharide examples: fructose, sucrose, glucose, lactose, mannitol (claim 27)
Disintegrant exemplars (claim 28):
- cross-linked sodium carboxymethylcellulose
- crospovidone
Surfactant and plasticizer exemplars (claims 29-30):
- surfactant: polysorbate
- plasticizer: polyethylene glycol
Exposure/outcome claims (PK-defined scope expansion and enforcement leverage)
The patent pushes enforceability beyond “formulation parameters” into plasma exposure metrics.
Fed vs fasted exposure ratios:
- ratio of mean plasma AUC(0-τ) fed to fasted: 1:1 to 4:1 (claim 31)
- ratio of mean plasma Cmax fed to fasted: 1.5:1 to 7:1 (claim 32)
Absolute exposure targets at fasted state (adult subjects, oral doses):
- AUC 0-24 hours: *100 to 375 ngh/mL for 200 to 500 mg** dose (claim 33)
- Cmax: 25 to 70 ng/mL for 200 to 500 mg dose (claim 34)
Absolute exposure targets at fed state:
- AUC (0-48 hours): *400 to 1200 ngh/mL** (claim 35)
- Cmax: 60 to 250 ng/mL (claim 36)
Steady-state fluctuation ceiling:
- Cmax/Cmin not greater than about 4:1 at steady state for 200 to 500 mg dose (claim 37)
Immediate vs controlled release:
- immediate release (claim 38)
- controlled release (claim 39)
- controlled release architecture:
- controlled release component (first portion)
- immediate release component (second portion)
- both portions with D50 50 to 500 nm
- ganaxolone distribution ratio controlled release:immediate release 4:1 to 1:4 (claim 40-41)
- duration target: therapeutic effect 8 to 24 hours (claim 42)
Secondary particle size and D50 variants
- baseline D50 (claim 1): 50 to 500 nm
- dependent D50 in distilled water: 100 to 350 nm (claim 10)
- a separate dependent claims broader D50: 50 to 1000 nm (claim 33), tied to PK windows (AUC 0-24 hours 100 to 375 ng*h/mL for 200 to 500 mg fasted).
This creates a claim strategy where the patent can still capture variants with different particle size ranges if they achieve the same PK outcomes.
What is the practical “infringement map” created by the claim language?
A. Must-have formula elements
A product that avoids infringement would likely need to change at least one of these required elements in the claim-1 chain:
- Particle size D50 50 to 500 nm
- Ganaxolone content at least 50% by weight
- Hydrophilic polymer class
- Wetting agent
- Complexing agent definition:
- MW < 550 and moiety in phenol/aromatic ester/aromatic acid categories
- SGF/SIF stability behavior if dependents 4-7 are implicated (D50 growth <= 150%, SGF/SIF D50 < 750 nm)
B. “Value-added” dependent claim hooks
For freedom-to-operate and design-around, the most meaningful dependent claim hooks are:
- Specific exemplars: hydroxypropylmethylcellulose, polyvinyl alcohol, sodium lauryl sulfate, docusate, methylparaben/benzoic acid/methyl anthranilate
- Hard SGF/SIF test conditions (0.5 to 1 mg/mL, 36-38°C, 1 hour; D50 increase <=150%, SGF/SIF D50 < 750 nm)
- PK windows (fed/fasted AUC/Cmax ratios and absolute exposures for 200-500 mg)
- Dosage architecture (controlled release vs immediate release components and their ganaxolone portion ratio)
How broad is the indication coverage?
The claim set includes multiple CNS and neuropsychiatric conditions, plus several additional disease categories that are not purely neurological in conventional classification:
- hypertension and pain are listed in the same “CNS disorder” set
- Niemann Pick disease Type-C and Mucolipidosis Type IV lipid accumulation are metabolic/neurodegenerative
- Alzheimer’s, Huntington’s, Parkinson’s are classic neurodegenerative
- epilepsy syndromes and anxiety/panic/depression/insomnia are psychiatric and sleep domains
From a landscape perspective, that breadth matters because it can expand potential enforcement targets across multiple therapeutic programs that use the same drug and oral nanoparticle technology, even when label/indication is different in downstream development.
What does claim replication in later claims imply for coverage?
Claims 49-54 replicate much of claim 1’s structure and tighten it by restating complexing agent presence (including the 0.05% to 5% w/w range). That replication increases enforceability by ensuring that even if a challenger targets claim 1’s complexing agent definition, there are overlapping claim paths that still require:
- solid stabilized particles with ganaxolone + hydrophilic polymer + wetting agent
- D50 50 to 500 nm
- complexing agent MW < 550 with the moiety category
- plus, at least in claim 49, a specific complexing agent amount range
US patent landscape: where this patent sits relative to competing ganaxolone oral formulations
1) Technology focus: solid stabilized particles with complexing agents
The claims specifically require a complexing agent small organic molecule (MW < 550) with phenol/aromatic ester/aromatic acid moiety, in addition to a hydrophilic polymer and wetting agent.
That combination is a distinctive claim anchor. It differentiates this technology from ganaxolone formulations that rely only on:
- micronization
- lipid-based delivery
- cyclodextrin-only inclusion complexes without the moiety/MW framework
- polymer-only stabilization without the defined aromatic small-molecule complexing agent
Even without full bibliographic mapping of all related patents, the claim language creates a clear enforcement perimeter: if the competitor’s oral formulation lacks a complexing agent satisfying the moiety/MW limits, claim coverage is harder to reach.
2) Enforced product attributes: nanoparticles and SGF/SIF dispersion stability
The patent requires:
- D50 50 to 500 nm, and in dependents, SGF/SIF D50 < 750 nm with limited growth
- test conditions tied to SGF/SIF heated incubation
This suggests the landscape around ganaxolone oral tech splits into:
- approaches that accept significant particle growth in GI media (harder to capture by these dependent claims)
- approaches that control colloidal stability and retain submicron dispersion after SGF/SIF exposure
3) Enforced pharmacokinetics (PK)
By building in numeric plasma exposure windows and fed/fasted ratios, the patent extends enforcement arguments to formulation effects that manifest in vivo.
Competitors can avoid infringement by changing formulation parameters, but if clinical PK profiles align with these windows, the patent may still have leverage through dependent claims (31-37, 33-36). The risk is higher when developers market “same drug, same dose, improved oral exposure” because their in vivo profiles may land within these numeric bands.
4) Dosage form architecture (IR/CR)
The controlled release dependent claims create another enforcement lane:
- two-component architecture with controlled-release and immediate-release fractions of stabilized particles
- specified ganaxolone distribution ratio between controlled and immediate release fractions
- duration 8-24 hours
In the broader landscape, many oral programs either:
- stay purely immediate release
- use different controlled-release matrices (e.g., osmotic pumps, lipid matrices, coated pellets)
This claim set is narrower because it requires particle-based split fractions with specific D50 constraints.
Key claim dimensions for landscape screening (fast FTO triage)
Use this checklist to categorize a competitor’s ganaxolone oral solid:
| Dimension |
Claim anchor |
Pass/fail logic for FTO screening |
| Particle size |
D50 50-500 nm |
Product must keep D50 within range (and in dependents, 100-350 in water or SGF/SIF D50 < 750 nm) |
| Loading |
ganaxolone >=50% by weight (and in claim 6, up to ~80%) |
Competitor must use lower loading or a different structure |
| Complexing agent |
small organic molecule MW < 550 with phenol/aromatic ester/aromatic acid moiety |
A formulation without such a complexing agent is less exposed |
| Complexing agent dose |
0.05%-5% w/w (claim 43) |
If outside, dependent coverage weakens |
| Hydrophilic polymer |
3%-50% w/w in dependents |
Out-of-range polymer loading can reduce risk |
| Wetting agent |
0.01%-10% w/w in dependents |
Out-of-range wetting can reduce risk |
| GI stability |
D50 growth <=150% in SGF/SIF; SGF/SIF D50 < 750 nm |
Competitor must demonstrate poor fit if they cannot maintain stability |
| Dosage form |
powder; tablets/capsules; IR/CR variants |
If competitor uses completely different delivery architecture, dependent claims narrow exposure |
| PK endpoints |
AUC/Cmax windows and ratios |
If PK lands in windows, dependent claim leverage increases |
Key Takeaways
- US 8,618,087 claims oral treatment of a wide CNS disorder set using ganaxolone solid stabilized particles with D50 50 to 500 nm and ganaxolone at least 50% by weight.
- The formulation is defined by a three-part physical-chemical system: hydrophilic polymer + wetting agent + MW<550 aromatic moiety complexing agent.
- The enforceable perimeter tightens in dependents through SGF/SIF stability metrics (D50 growth <=150%, SGF/SIF D50 < 750 nm under specified conditions).
- The patent adds in vivo PK numeric windows for 200 to 500 mg oral dosing in fasted and fed states, plus fed/fasted ratios and steady-state Cmax/Cmin.
- Landscape screening should focus first on whether a competitor uses an aromatic small-molecule complexing agent meeting the moiety/MW definition, then on nanoparticle size retention in SGF/SIF, then on PK landing zones.
FAQs
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Does US 8,618,087 require controlled release?
No. Claim 1 covers administration of solid stabilized particles generally; controlled release is covered only in dependent claims (claims 39-42).
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What particle size range is central to claim coverage?
The independent claim requires D50 of 50 nm to 500 nm. Dependent claims also constrain SGF/SIF outcomes (SGF/SIF D50 < 750 nm and limited growth).
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Is the complexing agent defined only by generic categories or by specific numeric constraints?
Both. It is defined as a small organic molecule with MW < 550 and a phenol/aromatic ester/aromatic acid moiety category. Dependent claims further provide examples (methylparaben, benzoic acid, methyl anthranilate) and a 0.05% to 5% w/w range.
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Can a competitor avoid risk by using different hydrophilic polymers?
The independent claim covers hydrophilic polymer generally, but dependent claims narrow to specific polymer families and specific exemplars (cellulose ether/hydroxypropylmethylcellulose; polyvinyl alcohol). Avoiding those exemplars may reduce dependent claim exposure but not necessarily independent claim exposure if all other elements match.
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How do the PK claims affect landscape competition?
They expand the enforceable scope into numeric plasma AUC/Cmax targets for 200 to 500 mg dosing in fasted and fed conditions and fed/fasted ratios. Formulations that meet formulation parameters but shift PK outside the bands may avoid those dependent claims.
References
[1] United States Patent 8,618,087 (ganaxolone solid stabilized particles and methods of treating CNS disorders).
