US Patent 9,101,540: Megestrol Acetate Nanoparticulate Suspension Patent Analysis

US Patent 9,101,540 protects specific nanoparticulate megestrol acetate oral suspensions, particularly low-viscosity liquid formulations using hydroxypropyl methylcellulose and dioctyl sodium sulfosuccinate. The strongest claim limitations are the sub-150 nm particle size, megestrol acetate concentration of approximately 115 to 135 mg/mL, dose equivalence to 800 mg of conventional megestrol acetate, and specified pharmacokinetic results. The patent does not cover every megestrol acetate suspension or every nanocrystal formulation.

The claims supplied are composition, pharmacokinetic, and method-of-treatment claims. They create potential infringement exposure for a product that combines the claimed particle size, stabilizer system, concentration, dose conversion, and clinical performance.

What does US Patent 9,101,540 protect?

The patent protects pharmaceutical compositions and treatment methods based on nanoparticulate megestrol acetate. The core technology reduces the particle size of megestrol acetate and uses surface stabilizers to improve dispersion, absorption, and dosing efficiency.

Core claim architecture

Claim group	Subject matter	Principal limitations
Claim 1	Stable oral suspension	Nanoparticulate megestrol acetate below 150 nm; 115-135 mg/mL; 575-675 mg composition bioequivalent to 800 mg conventional product
Claims 2-5	Dose and food-effect limitations	115, 125, or 135 mg/mL; reduced or non-significant fed/fasted absorption difference
Claims 6-7	Pharmacokinetic compositions	HPMC and DOSS; 575 mg or 625 mg megestrol acetate; specified Cmax and AUC values
Claims 8-9	Treatment method	Oral administration to a fasted subject; Cmax of approximately 300-2,000 ng/mL; Cmax greater than standard product
Claims 10-18	Particle form and stabilizers	Crystalline, amorphous, or semi-crystalline drug; particle-size subranges; broad stabilizer classes
Claims 19-20	Rheology	Viscosity substantially lower than a standard commercial liquid product
Claims 21-25	Narrow combinations and particle-size ranges	HPMC/DOSS combination and particle sizes greater than selected lower thresholds

The patent is therefore a formulation and performance patent rather than a broad compound patent. It does not claim the megestrol acetate molecule itself.

How should independent claim 1 be interpreted?

Claim 1 requires a combination of structural, quantitative, and performance limitations. A potentially infringing product would need to satisfy all material limitations.

Claim 1 limitation chart

Limitation	Required scope	Commercial significance
Dosage form	Stable oral suspension	Excludes tablets, capsules, injectables, and unstable suspensions
Active ingredient	Nanoparticulate megestrol acetate	Requires a particle-engineered formulation
Particle size	Effective average particle size below 150 nm	The central nanocrystal limitation
Concentration	Approximately 115-135 mg/mL in water	Focuses the claim on a concentrated suspension
Surface stabilizer	At least one stabilizer adsorbed on the particle surface	Requires more than a conventional excipient merely present in the vehicle
Dose relationship	Approximately 575-675 mg is bioequivalent to 800 mg conventional composition	Links the formulation to a reduced-volume or reduced-dose-equivalent product

The phrase “effective average particle size” is likely to be measured using a particle-size distribution method rather than by identifying the largest or smallest individual particles. A formulation with a mean or effective average below 150 nm may fall within the claim even if isolated particles are larger.

The concentration limitation is material. A product at 100 mg/mL or 150 mg/mL may avoid literal infringement of claim 1, subject to the doctrine of equivalents and the scope of other claims or related patents.

What formulations are protected by US 9,101,540?

The protected formulation profile is a low-viscosity, high-concentration liquid suspension containing sub-150 nm megestrol acetate particles and one or more surface stabilizers.

HPMC and DOSS formulation

Claims 6, 7, 16, and 21 specifically identify:

Hydroxypropyl methylcellulose, commonly HPMC
Dioctyl sodium sulfosuccinate, commonly DOSS or docusate sodium
Nanoparticulate megestrol acetate below 150 nm

Claims 6 and 7 add pharmacokinetic limitations:

Claim	Megestrol acetate amount	Fed-state Cmax	Fed-state AUC∞
6	Approximately 575 mg	1,421 ± 421 ng/mL	14,743 ± 4,451 h·ng/mL
7	Approximately 625 mg	1,517 ± 389 ng/mL	16,082 ± 5,563 h·ng/mL

These claims are narrower than claim 1 because they require both the HPMC/DOSS stabilizer combination and particular pharmacokinetic results. They may be difficult to enforce without reliable clinical or comparative bioequivalence data. A generic applicant’s formulation development and bioequivalence studies could become important evidence.

Other stabilizers

Claim 18 contains an unusually broad list of possible stabilizers. It includes polymers, surfactants, ionic compounds, nonionic compounds, phospholipids, celluloses, poloxamers, quaternary ammonium compounds, and other surface-active materials.

The breadth of claim 18 is limited by its dependency on claim 1. A stabilizer listed in claim 18 does not independently create infringement. The product must also satisfy the claim 1 limitations, including particle size, concentration, oral suspension format, and dose-equivalence limitation.

How broad are the particle-size claims?

The principal threshold is less than 150 nm. Claim 11 narrows the range to less than:

100 nm
75 nm
50 nm

Claims 22 through 24 introduce lower-bound limitations greater than 50 nm, greater than 75 nm, or greater than 100 nm. These claims create nested particle-size windows, including:

Claim concept	Approximate particle-size range
Claim 1	Below 150 nm
Claim 11	Below 100 nm, 75 nm, or 50 nm
Claim 22	Greater than 50, 75, or 100 nm and below 150 nm
Claim 23	Same type of range for claim 6
Claim 24	Same type of range for claim 7

A product with an average particle size of 120 nm may be relevant to claim 1 and claim 22. A product below 50 nm may implicate claim 1 and claim 11 but would not satisfy a “greater than 50 nm” limitation.

Particle-size measurement conditions matter. Milling method, dilution medium, analytical instrument, distribution metric, and sample preparation can affect the reported effective average size. These parameters would likely be central in an infringement dispute.

What protection exists for food-effect performance?

Claims 3 through 5 address the difference between fed and fasted absorption. The claimed difference may be less than 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 25%, 20%, 15%, 10%, 5%, or 3%.

Claim 4 selects a difference of less than approximately 60%. Claim 5 covers a composition that does not produce significantly different absorption levels under fed and fasted conditions.

These claims target a known commercial problem with conventional megestrol acetate suspensions: variable absorption depending on administration with food. A formulation that demonstrates limited food effect may be exposed even if its excipient system differs from HPMC/DOSS, provided it meets the other limitations of the parent claim.

The food-effect claims are evidence-dependent. A sponsor’s fed and fasted pharmacokinetic studies would be relevant to whether the limitation is met. Regulatory bioequivalence data could provide useful evidence, although FDA acceptance of bioequivalence does not itself decide patent infringement.

What do claims 6 and 7 protect?

Claims 6 and 7 are narrow product-by-performance claims.

Claim 6 requires:

Nanoparticulate megestrol acetate below 150 nm.
HPMC and DOSS as surface stabilizers.
Approximately 575 mg of megestrol acetate.
Fed-state Cmax of 1,421 ± 421 ng/mL.
Fed-state AUC∞ of 14,743 ± 4,451 h·ng/mL.

Claim 7 substitutes approximately 625 mg and a second pharmacokinetic profile.

The numerical ranges implied by the reported means and standard deviations are:

Claim	Cmax range using ±1 standard deviation	AUC∞ range using ±1 standard deviation
6	1,000-1,842 ng/mL	10,292-19,194 h·ng/mL
7	1,128-1,906 ng/mL	10,519-21,645 h·ng/mL

The claims do not expressly state whether infringement requires the accused product to produce results within those statistical intervals in an independent study or whether the data are product characteristics defined by the claim. That issue could create litigation over claim construction and proof.

What do claims 8 and 9 protect?

Claims 8 and 9 cover a method of treating:

Anorexia
Cachexia
Loss of body mass

The method requires oral administration of nanoparticulate megestrol acetate to a fasted human subject, with a Cmax of approximately 300-2,000 ng/mL. Claim 9 adds a comparative requirement: the Cmax must exceed approximately 100% of the Cmax of a standard commercial megestrol acetate composition administered at the same dosage.

These claims create potential method-of-use exposure for a product label directed to appetite stimulation, cachexia, or weight loss. They are less likely to reach an accused manufacturer solely through product composition if the manufacturer does not induce the claimed administration method.

The “fasted human subject” requirement is significant. A label that instructs administration without regard to food may create a different infringement analysis from a label that specifically directs administration in the fasted state.

How strong is the patent estate based on the supplied claims?

The supplied claims provide moderate formulation coverage but have several narrowing features.

Strengths

The sub-150 nm limitation distinguishes the claimed product from ordinary microparticulate suspensions.
HPMC/DOSS coverage targets a specific stabilizer combination.
Claims address composition, pharmacokinetics, food effect, viscosity, and treatment use.
The 575-675 mg to 800 mg bioequivalence relationship connects the formulation to a clinically relevant commercial dose.
The claims can cover alternative crystalline, amorphous, and semi-crystalline forms.
Claim 18 lists a broad range of possible stabilizers.

Vulnerabilities

Claim 1 requires several limitations to be met simultaneously.
The 115-135 mg/mL concentration range creates a design-around opportunity.
A formulation above 150 nm may avoid the principal nanoparticulate limitation.
A formulation using a different particle-engineering approach may challenge the “surface stabilizer adsorbed” limitation.
Claims 6 and 7 depend on precise pharmacokinetic outcomes that may vary by study population and protocol.
The viscosity claims require comparative testing against a standard commercial formulation.
Claims 8 and 9 require human pharmacokinetic results and specified administration conditions.
Claim 25 appears internally anomalous because it refers to “the method of claim 7,” although claim 7 is drafted as a composition claim. That dependency issue could affect enforceability or construction.

What generic launch risks exist?

A generic or follow-on manufacturer faces the highest risk if it develops a product with the following profile:

Risk factor	High-risk characteristic
Particle size	Effective average below 150 nm
Concentration	115-135 mg/mL
Stabilizers	HPMC plus DOSS
Dose	Approximately 575 mg or 625 mg
Product type	Stable oral suspension
Performance	Bioequivalent to 800 mg conventional megestrol acetate
Label	Treatment of anorexia, cachexia, or loss of body mass
Administration	Fasted-state or food-effect language
Rheology	Much lower viscosity than the commercial suspension

A lower-risk design could use a particle size of at least 150 nm, a concentration outside 115-135 mg/mL, a different stabilizer system, or a product that does not rely on the claimed reduced-dose bioequivalence relationship. Those changes would not eliminate risk under related patents or the doctrine of equivalents.

What is the FDA and Orange Book significance?

Megestrol acetate oral suspensions are approved prescription products used primarily for anorexia, cachexia, or significant weight loss associated with AIDS. FDA labeling distinguishes conventional oral suspensions from concentrated formulations such as Megace ES. The FDA label identifies Megace ES as a 625 mg/5 mL oral suspension, equivalent to 125 mg/mL, which is within the concentration range recited in claim 2 of US 9,101,540.[2]

That concentration overlap is commercially important. A product corresponding to a 625 mg/5 mL concentrated suspension may fall within the numerical concentration limitation, but infringement still requires the nanoparticulate size, surface-stabilizer, stability, and dose-equivalence limitations.

An Orange Book listing cannot be established from the claim text alone. The relevant regulatory analysis requires the specific FDA-approved product, patent-listing record, delisting history, and any applicable expiration-date or pediatric-exclusivity information. A patent’s existence does not establish that it is listed for a particular product.

What Paragraph IV and litigation issues are relevant?

A generic applicant challenging a listed patent would typically evaluate:

Non-infringement based on particle size, concentration, stabilizer, or dose.
Invalidity for anticipation or obviousness.
Lack of written description or enablement for broad stabilizer and performance limitations.
Indefiniteness involving “effective average particle size,” “stable,” “bioequivalent,” “significantly different,” and pharmacokinetic ranges.
Written-description support for the extensive stabilizer list.
Enforceability of claims with unusual or defective dependency language, including claim 25.
Patent-term and Orange Book listing issues.

The most credible design-around arguments would focus on a particle size at or above 150 nm, a concentration outside the 115-135 mg/mL range, or omission of HPMC/DOSS. The strongest invalidity arguments would likely target the combination of known nanoparticulate drug technology, conventional megestrol acetate formulations, known surfactants, and predictable pharmacokinetic advantages. The patentee would counter that the specific concentration, reduced dose, food-effect profile, and clinical pharmacokinetic results were not predictable from the prior art.

No litigation, settlement, or Paragraph IV outcome is established by the claim text supplied.

How does this patent compare with conventional megestrol acetate products?

Attribute	Conventional suspension	Claimed nanoparticulate formulation
Particle scale	Microparticulate or unspecified	Effective average below 150 nm
Concentration	Often lower concentration	Approximately 115-135 mg/mL
Dose efficiency	Conventional 800 mg reference dose	Approximately 575-675 mg composition equivalent to 800 mg
Food effect	May be clinically relevant	Claims seek reduced or non-significant food effect
Stabilization	Conventional suspension excipients	Surface-adsorbed stabilizer required
Viscosity	Standard commercial liquid viscosity	Claims cover substantially reduced viscosity
Regulatory relevance	Conventional oral suspension	Concentrated suspension comparable to Megace ES

What is the likely commercial exposure?

The principal commercial exposure is concentrated megestrol acetate oral suspension. A product corresponding to 625 mg/5 mL has a direct numerical relationship to claim 2’s 125 mg/mL limitation and to claims 7 and 21’s 625 mg formulation.

Revenue exposure depends on whether the patent is listed and enforceable against the marketed product, whether a generic applicant certifies Paragraph IV, and whether related patents cover the same product. The supplied material does not provide verified sales, market-share, patent-listing, expiration, litigation, or settlement data. Those matters cannot be derived from the claims.

Key Takeaways

US 9,101,540 is a formulation and method patent, not a patent on megestrol acetate itself.
The central claim requires a stable oral suspension containing megestrol acetate particles below 150 nm.
Claim 1 also requires approximately 115-135 mg/mL and a 575-675 mg dose that is bioequivalent to 800 mg of conventional megestrol acetate.
HPMC and DOSS are the most commercially important stabilizers specifically identified in the claims.
Claims 6 and 7 depend on narrow Cmax and AUC values, making pharmacokinetic testing central to infringement analysis.
A 625 mg/5 mL product has the same 125 mg/mL concentration recited in claim 2, but concentration alone is insufficient for infringement.
The most practical design-around strategies are particle size of at least 150 nm, concentration outside the claimed range, or a materially different stabilizer system.
The supplied claims do not establish Orange Book listing, patent expiration, Paragraph IV activity, litigation, settlements, or revenue exposure.
Claim 25 contains a potentially material dependency defect because it refers to claim 7 as a method claim.

FAQs

Does US 9,101,540 cover Megace ES?

The claims are technically aligned with a concentrated nanoparticulate megestrol acetate suspension, including a 125 mg/mL concentration and 625 mg dose embodiment. The claim text alone does not establish the approved product’s complete patent coverage or Orange Book listing.

Can a generic avoid the patent by using a different stabilizer?

Potentially. A product that does not use HPMC and DOSS may avoid claims 6, 7, and 21, but claim 1 and other dependent claims may still apply if the product uses another adsorbed surface stabilizer and meets the remaining limitations.

Is a 150 nm megestrol acetate formulation outside the patent?

A formulation with an effective average particle size of exactly or greater than 150 nm would generally fall outside the “less than 150 nm” limitation. Other patents, claims, or an equivalents theory could still create risk.

Does bioequivalence to 800 mg automatically establish infringement?

No. Bioequivalence alone does not satisfy every limitation. The accused product must also meet the particle-size, concentration, suspension, stabilizer, and other applicable claim requirements.

What is the strongest invalidity issue?

The principal issues are whether prior art disclosed or rendered obvious the specific combination of sub-150 nm megestrol acetate particles, the claimed concentration and dose conversion, the stabilizer system, and the reported pharmacokinetic performance. The broad stabilizer list and performance-defined limitations may also raise written-description, enablement, or indefiniteness issues.

References

United States Patent No. 9,101,540, claims 1-25. U.S. Patent and Trademark Office.
U.S. Food and Drug Administration. (n.d.). Megace ES (megestrol acetate) oral suspension prescribing information. FDA-approved labeling.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	539737	⤷ Start Trial
Australia	2003230885	⤷ Start Trial
Australia	2003231071	⤷ Start Trial
Australia	2006262144	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 9,101,540

Summary for Patent: 9,101,540