US Patent 9,101,549: Claim Scope, Expiration, Orange Book Status, and Megestrol Patent Landscape

US Patent 9,101,549 protects a once-daily nanoparticulate megestrol acetate oral suspension for treating anorexia, cachexia, or loss of body mass. Its commercial value comes from the combination of four limitations: dose and volume, particle-size distribution, surface stabilization, and reduced food effect. The patent is a method-of-treatment patent, not a standalone composition patent.

The claims are directed primarily to Megace ES-type formulations and potentially competing formulations that reproduce the claimed pharmacokinetic profile. The patent’s base statutory term is tied to its earliest effective nonprovisional priority date, with any patent-term adjustment determined by the USPTO. The FDA’s three-year regulatory exclusivity for Megace ES is separate from patent protection and expired years earlier.

What does US Patent 9,101,549 cover?

Claim 1 requires all of the following:

Claim element	Required limitation
Patient	Human patient
Disease or condition	Anorexia, cachexia, or loss of body mass
Active ingredient	Megestrol acetate
Dose	About 40 mg to about 800 mg
Administration volume	About 5 mL
Dosage form	Oral suspension
Particle size	About 80% of particles between or equivalent to about 250 nm and about 50 nm
Stabilization	At least one surface stabilizer associated with the particle surface
Dosing frequency	Once daily
Food-effect result	Fed-versus-fasted Cmax difference below about 60%
Pharmacokinetic test	Single administration in a human subject
Fed condition	High-calorie meal within approximately 30 minutes of dosing
Fasted condition	No food for at least 10 hours before dosing

The claim is narrow because a formulation must satisfy both structural and performance limitations. A product that uses megestrol acetate nanoparticles but does not meet the claimed dose, 5 mL volume, once-daily regimen, particle-size distribution, and Cmax food-effect limitation would not literally meet claim 1.

How do the dependent claims narrow the patent?

Claims 2 through 23 create multiple fallback positions.

Disease-specific claims

Claims 3 and 4 limit the indication:

Claim 3 covers anorexia, cachexia, or body-mass loss associated with HIV or AIDS.
Claim 4 covers the same conditions associated with cancer.

These claims could be relevant to labeling, promotional activity, prescribing instructions, or induced-infringement theories directed to HIV/AIDS or cancer populations.

Pharmacokinetic claims

Claims 5 through 12 progressively reduce the allowed fed-versus-fasted Cmax difference:

Claim	Maximum Cmax difference
1	Less than about 60%
5	Less than about 50%
6	Less than about 40%
7	Less than about 30%
8	Less than about 20%
9	Less than about 15%
10	Less than about 10%
11	Less than about 5%
12	Less than about 3%

These claims are valuable only if the claimed pharmacokinetic result is reproducible under the specified fed and fasted conditions. A generic applicant could challenge the claims by arguing that the Cmax limitation is indefinite, inherently variable, or not demonstrated across the full claimed formulation and dosage range.

Claim 13 adds a fed-versus-fasted mean Tmax limitation. Claim 15 adds an AUC limitation, with a maximum difference ranging from 35% to 3%.

Claims 16 through 20 impose additional concentration and absorption-time requirements:

Cmax attained within about one hour in fasting subjects.
Maximum plasma concentration of at least about 700 ng/mL.
At least about 400 ng/mL within five hours.
Mean fasted Cmax between about 300 ng/mL and about 2,000 ng/mL.
Cmax at least about 700 ng/mL within five hours when combined with the AUC limitation.

These claims create substantial testing burdens because infringement may depend on clinical pharmacokinetic data rather than simply on the product label.

Surface-stabilizer claims

Claim 21 broadly covers nonionic, cationic, ionic, and zwitterionic surfactants.

Claim 22 identifies specific stabilizers, including:

Hydroxypropyl methylcellulose;
Hydroxypropylcellulose;
Polyvinylpyrrolidone;
Sodium lauryl sulfate;
Dioctylsulfosuccinate;
Polyoxyethylene alkyl ethers;
Polyoxyethylene sorbitan fatty acid esters;
4-(1,1,3,3-tetramethylbutyl)-phenol polymer with ethylene oxide and formaldehyde;
Lysozyme; and
Random copolymers of vinylpyrrolidone and vinyl acetate.

Claim 23 narrows the stabilizer to hydroxypropyl methylcellulose, dioctylsulfosuccinate, or a combination of the two.

What is the strongest enforceable scope of claim 1?

The strongest practical scope is the intersection of the following characteristics:

A megestrol acetate nanosuspension;
A particle-size distribution centered in the approximately 50 nm to 250 nm range;
A surface stabilizer;
A 40 mg to 800 mg dose in approximately 5 mL;
Once-daily administration;
Treatment of wasting-related conditions; and
Low fed-versus-fasted variability in Cmax.

The patent does not claim every megestrol acetate suspension. Conventional micronized or non-nanoparticulate suspensions fall outside the structural limitation unless they satisfy the claimed particle-size distribution. Conversely, a nanoparticulate formulation may still avoid infringement if it is administered in a different volume, uses a different dosing frequency, or lacks the claimed pharmacokinetic profile.

The most contestable terms are the following:

“About 80%”;
“Between or equivalent to”;
“About 250 nm and about 50 nm”;
“Associated with the surface”;
“Difference in Cmax”;
“High-calorie meal”;
“Standard commercial, non-nanoparticulate composition”; and
“Same dosage.”

The wording in claim 1 appears to place the particle-size endpoints in descending order, while claim 2 clarifies the narrower range as approximately 70 nm to 230 nm. A court would likely construe the particle-size language using the specification, prosecution history, particle-sizing methodology, and the meaning of “about.”

What formulations are protected by US Patent 9,101,549?

The patent is directed to nanoparticulate oral suspensions rather than tablets, capsules, implants, or injectable products. A qualifying formulation must be administered as an oral suspension in approximately 5 mL.

A formulation is more exposed when it has:

Nanoparticulate megestrol acetate;
Hydroxypropyl methylcellulose or dioctylsulfosuccinate;
A 40 mg, 200 mg, 400 mg, or 800 mg dose;
Once-daily administration;
A clinical or label-based claim of reduced food effect; and
Pharmacokinetic data showing rapid absorption or a Cmax in the claimed range.

The patent does not require a particular commercial excipient concentration, viscosity, flavoring system, preservative, or container. Those features may be covered by other formulation patents or may be relevant to bioequivalence and product-quality analysis.

How does the patent compare with earlier megestrol patents?

The relevant megestrol patent estate is divided into several technology groups.

Patent group	Principal subject matter	Strategic relevance
Conventional megestrol formulations	Suspensions, tablets, dosage forms	Earlier formulation protection; generally weaker against later nanoparticulate products
Nanoparticulate megestrol compositions	Particle size and surface stabilization	Core technology underlying Megace ES-type products
Pharmacokinetic and food-effect claims	Reduced fed-versus-fasted variability, Cmax, Tmax, and AUC	Protects clinical performance rather than only formulation structure
Method-of-treatment claims	Treatment of anorexia, cachexia, HIV/AIDS-related wasting, and cancer-related wasting	Relevant to labeled use and induced infringement
Manufacturing and process claims	Milling, precipitation, stabilization, homogenization, and suspension manufacture	Can create supply-chain barriers even when treatment claims expire

US Patent 9,101,549 is most significant as a later-generation method patent that links nanoparticle structure to a clinical pharmacokinetic result. It is narrower than a composition patent but may be harder to design around if the commercial product’s performance depends on the same nanoparticle platform.

What is the Orange Book status of Megace ES?

Megace ES is the branded high-concentration megestrol acetate oral suspension associated with the nanoparticulate formulation technology. FDA approval and Orange Book listing are separate from patent ownership.

Regulatory item	Status
Active ingredient	Megestrol acetate
Dosage form	Oral suspension
Reference product	Megace ES
FDA pathway	NDA
Regulatory category	Small-molecule drug
Regulatory exclusivity	Three-year exclusivity associated with an approved change, not current market exclusivity
Orange Book relevance	Reference listed drug status supports ANDA competition
Biosimilar pathway	Not applicable

The FDA approved Megace ES under NDA 21-778. FDA approval records identify the product as a megestrol acetate oral suspension used to treat anorexia, cachexia, or unexplained significant weight loss in patients with AIDS. The approved labeling also describes the formulation and food-effect characteristics relevant to the patent claims (FDA, 2005).

The patent number at issue must be checked against the current Orange Book patent table for the reference product. A patent can remain legally relevant without being listed in the Orange Book, and an Orange Book listing does not establish validity or infringement.

When does US Patent 9,101,549 lose exclusivity?

Patent expiration and FDA exclusivity must be analyzed separately.

Patent term

US Patent 9,101,549 issued on August 11, 2015. Its expiration is governed by the earliest effective nonprovisional priority date, subject to patent-term adjustment and any terminal disclaimer. The patent is not eligible for patent-term extension merely because the product received FDA approval unless the statutory requirements for a qualifying regulatory review period are satisfied.

The principal business conclusion is that the patent’s base term is tied to an early-2000s priority chain and is therefore materially shorter than a patent filed in 2014 would imply. The operative expiration date should be taken from the USPTO Patent Examination Data System and patent-term calculation records, not from the issue date.

FDA exclusivity

Megace ES’s three-year FDA exclusivity was regulatory exclusivity. It blocked certain abbreviated applications for the protected change during the exclusivity period but did not create a patent term. That period expired well before the current market period.

Pediatric exclusivity

No six-month pediatric exclusivity is associated with the supplied claim set. Pediatric exclusivity, if granted, would attach to an FDA-listed product and would be shown in FDA regulatory records.

Which companies are challenging Megace ES exclusivity?

Competition is expected to come from manufacturers of generic megestrol acetate oral suspensions rather than biosimilar developers. Megestrol acetate is a chemically synthesized small molecule, so the Public Health Service Act biosimilar pathway does not apply.

An ANDA applicant could challenge listed patents through a Paragraph IV certification. The principal litigation theories would include:

Invalidity based on anticipation;
Obviousness over earlier nanoparticulate drug-delivery patents;
Lack of written description for the full dose and particle-size ranges;
Lack of enablement for the full pharmacokinetic result;
Indefiniteness of “about,” “equivalent to,” and “difference in Cmax”;
Noninfringement based on particle size, dose volume, stabilizer, or dosing frequency; and
Failure to establish infringement from product-label information alone.

A generic applicant may also use a Paragraph III certification if a listed patent remains in force and the applicant accepts delayed approval until expiration. A Paragraph IV filing can trigger Hatch-Waxman litigation and a potential 30-month stay under the statutory conditions (21 U.S.C. § 355(j)).

What patent litigation affects the commercial opportunity?

The key litigation distinction is between direct product infringement and method-of-treatment infringement.

A generic oral suspension manufacturer may avoid direct infringement arguments by omitting a patented indication or by using a product label that does not instruct once-daily administration for a claimed patient population. That strategy is less effective if the reference product’s only clinically meaningful use is the patented indication and the generic label necessarily reproduces the same dosing instructions.

Potential litigation evidence would include:

ANDA formulation records;
Particle-size specifications;
Surface-stabilizer identity and concentration;
Comparative fed and fasted pharmacokinetic studies;
Proposed labeling;
Batch-release data;
Bioequivalence protocols; and
Technical documents showing whether Cmax and AUC limitations are met.

The claim set is therefore more litigation-intensive than a simple composition claim. Discovery would likely focus on formulation batches and pharmacokinetic testing rather than only on the ingredient list.

How strong is the patent estate for Megace ES?

The estate is mixed.

Strengths

Claim 1 combines multiple technical limitations that may be difficult to avoid while preserving the commercial performance of a nanosuspension.
Dependent claims cover several particle-size, Cmax, Tmax, and AUC thresholds.
Claims 21 through 23 identify stabilizer classes and specific stabilizers.
The claims connect formulation architecture with reduced food effect, a commercially relevant advantage over conventional suspensions.

Weaknesses

The claim language relies heavily on approximate measurements.
Several pharmacokinetic limitations require human testing and may vary across subjects.
The “standard commercial, non-nanoparticulate composition” comparator in claim 14 may create construction and reproducibility disputes.
The claims are method claims, which can be harder to enforce against a generic product when the generic label omits a patented use.
Earlier nanoparticulate drug-delivery patents may create obviousness and written-description challenges.

Overall, the patent is strongest against a product deliberately designed to replicate the Megace ES nanoparticulate platform and its reduced food effect. It is weaker against a conventional megestrol suspension, a product with materially different particle-size distribution, or a product labeled for a noncovered dosing regimen.

What generic launch scenarios exist?

Launch scenario	Patent and regulatory implication
Pre-expiration Paragraph IV launch	Requires a successful invalidity or noninfringement position, settlement, or litigation outcome
Post-expiration ANDA launch	Standard generic entry with no active patent barrier
Noninfringing conventional suspension	May avoid nanoparticle claims but must satisfy FDA requirements for equivalence
Label carve-out	May reduce method-of-use exposure if FDA permits omission of a patented use
Authorized generic	Can enter under the NDA holder’s authorization and may avoid Paragraph IV risk
Reformulated nanoparticulate product	May remain exposed to claims 1, 2, and 21 through 23
Alternative dose volume or frequency	Potential design-around, subject to clinical and regulatory feasibility

The commercial tradeoff is direct: a generic can reduce patent risk by departing from the reference formulation, but that departure may increase bioequivalence, tolerability, manufacturing, and market-substitution risk.

What manufacturing and IP barriers remain?

The principal manufacturing barrier is not the active ingredient. It is reproducible control of nanoparticle size, stabilizer adsorption, suspension uniformity, redispersibility, sedimentation, viscosity, and dose accuracy.

A competitor would need to control:

Particle-size distribution at the claimed thresholds;
Surface-stabilizer association;
Milling or precipitation conditions;
Homogenization energy;
Suspension physical stability;
Microbial control;
Container-closure performance; and
Fed and fasted pharmacokinetic variability.

Separate process patents, trade secrets, know-how, and regulatory data may remain relevant after expiration of the treatment claims. These barriers can delay market entry even when the core patent no longer blocks approval.

How does Megace ES compare with other appetite and cachexia products?

Megace ES competes with products and treatment approaches that do not share the same patent profile.

Product or approach	Active agent or modality	Patent risk relative to US 9,101,549
Megace ES	Megestrol acetate nanosuspension	Directly relevant
Conventional megestrol suspension	Megestrol acetate	Usually outside nanoparticle limitations
Dronabinol	Cannabinoid	No direct claim overlap
Corticosteroid therapy	Various corticosteroids	No direct claim overlap
Mirtazapine	Antidepressant	No direct claim overlap
Nutritional intervention	Non-drug treatment	No patent overlap with the claim set

Megestrol products carry clinical risks associated with thromboembolic events, adrenal suppression, hyperglycemia, and glucocorticoid effects. Those safety considerations affect prescribing and commercial substitution but do not narrow the literal patent claims.

Key Takeaways

US Patent 9,101,549 is a method patent covering once-daily administration of a nanoparticulate megestrol acetate oral suspension.
Claim 1 requires a dose of approximately 40 mg to 800 mg in approximately 5 mL, a defined nanoparticle distribution, a surface stabilizer, and a reduced fed-versus-fasted Cmax difference.
Claims 2 through 23 add narrower particle-size, disease, stabilizer, Cmax, Tmax, AUC, and plasma-concentration limitations.
The patent does not cover every megestrol acetate suspension.
The most exposed competitor is a Megace ES-like nanoparticulate oral suspension using comparable stabilizers and dosing.
Megestrol acetate is a small molecule, so biosimilar litigation is not relevant.
Generic competition proceeds through the ANDA framework, including Paragraph III or Paragraph IV certifications.
FDA exclusivity and patent term are separate. Megace ES’s three-year regulatory exclusivity expired long before the current market period.
Patent-term analysis must use the earliest effective priority date, USPTO patent-term adjustment, and any terminal disclaimer.
Manufacturing know-how and process control may remain commercial barriers after expiry of the method claims.

Frequently Asked Questions

Does US Patent 9,101,549 cover Megace ES itself?

It covers a method of administering a qualifying nanoparticulate megestrol acetate suspension. It does not claim every physical embodiment of Megace ES as a standalone composition.

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

Potentially. A different stabilizer may avoid claims 22 and 23, but claim 21 covers broad stabilizer classes. The product would also need to avoid the particle-size, dose, volume, dosing-frequency, and pharmacokinetic limitations.

Is a Paragraph IV challenge required for every generic megestrol product?

No. A Paragraph IV certification is required only to challenge a listed patent before expiration. A generic applicant may use a Paragraph III certification, a permitted label carve-out, or proceed after listed patent expiration.

Does a lower dose avoid infringement?

Not necessarily. Claim 1 covers approximately 40 mg to approximately 800 mg. A dose below the claimed lower boundary may avoid literal infringement, but the complete product and method must be analyzed, including equivalents and other patent claims.

Are the Cmax and AUC limitations easy to test?

They are testable through comparative pharmacokinetic studies, but the results depend on study design, fed and fasted conditions, subject population, sampling schedule, formulation batch, and statistical treatment. Those variables are central to infringement and validity disputes.

References

Food and Drug Administration. (2005). Megace ES (megestrol acetate) oral suspension prescribing information. U.S. Department of Health and Human Services.
Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.
United States Patent and Trademark Office. (2015). U.S. Patent No. 9,101,549, methods of treatment using nanoparticulate megestrol acetate formulations. U.S. Department of Commerce.
United States Patent and Trademark Office. (2024). Patent term adjustment and patent examination data records for U.S. Patent No. 9,101,549. U.S. Department of Commerce.
U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs, Megace ES NDA 21-778. U.S. Department of Health and Human Services.
21 U.S.C. § 355. (2024). Abbreviated applications for new drugs and patent certifications.

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

Details for Patent: 9,101,549

Summary for Patent: 9,101,549