US Patent 9,597,289: Simvastatin Oral Suspension Claims, Patent Scope, Exclusivity and Generic Risk

US Patent 9,597,289 protects a narrowly defined aqueous simvastatin oral suspension. The claims require a specified excipient system, simvastatin with a particle-size distribution of d90 no greater than 20 micrometers, and one of two dose strengths: 20 mg or 40 mg per 5 mL. The patent does not broadly cover simvastatin, all liquid formulations, or all oral suspensions.

The principal infringement risk is for a product that reproduces the claimed composition and particle-size limitation, including the specified buffering, suspending, preservative, surfactant, viscosity, antifoaming and vehicle components.

What does US Patent 9,597,289 protect?

The patent claims four independent compositions and four dependent flavored or sweetened versions.

Independent claim	Simvastatin per 5 mL	Methyl hydroxybenzoate	Simethicone	Sodium lauryl sulfate	Key scope
Claim 1	20 mg	8 mg	1 mg	0.05 mg	Core 20 mg/5 mL suspension
Claim 3	20 mg	9 mg	1 mg	0.05 mg	Alternative preservative level
Claim 5	40 mg	8 mg	2 mg	0.10 mg	Core 40 mg/5 mL suspension
Claim 7	40 mg	9 mg	2 mg	0.10 mg	Alternative preservative level

Claims 2, 4, 6 and 8 add:

Acesulfame potassium: 2.5 mg per 5 mL
Flavor: 15 mg per 5 mL

All eight claims require the same general excipient platform:

Magnesium aluminium silicate: 20 mg/5 mL
Propylene glycol: 75 mg/5 mL
Carmellose sodium: 10 mg/5 mL
Citric acid monohydrate: 3.75 mg/5 mL
Anhydrous disodium hydrogen phosphate: 11.25 mg/5 mL
Simethicone at either 1 mg or 2 mg/5 mL
Paraben preservatives
Sodium lauryl sulfate
Purified water in a quantity sufficient to make the suspension

The open-ended term “comprises” means that additional ingredients may be present, provided the accused product still contains every required element of the applicable claim.

How broad is the simvastatin particle-size limitation?

The particle-size limitation is central to every claim. The claims require “simvastatin having d90 ≦ 20 μm.”

A d90 value of 20 micrometers means that 90% of the measured particle population is at or below 20 micrometers under the applicable particle-size measurement method. The limitation is not equivalent to an average particle size of 20 micrometers. A product may have a low mean particle size and still fail the claim if more than 10% of its particles exceed the claimed d90 threshold.

The patent scope therefore depends on:

The particle-size distribution of the simvastatin used in the commercial product.
The analytical method used to measure d90.
Whether the relevant measurement is made before formulation, after formulation, or under another protocol.
Whether agglomeration occurs during manufacture or storage.
Whether the accused product contains simvastatin in the claimed particle-size condition.

A manufacturer that uses a materially larger simvastatin particle distribution may avoid literal infringement of the particle-size limitation, even if its excipient system is substantially identical. That design-around may create separate issues involving dissolution, sedimentation, redispersibility, dose uniformity and bioavailability.

What formulations are protected by US 9,597,289?

The 20 mg/5 mL formulations

Claims 1 through 4 cover a suspension containing 20 mg of simvastatin per 5 mL. The two independent formulation variants differ only in methyl hydroxybenzoate:

8 mg/5 mL in claim 1
9 mg/5 mL in claim 3

The dependent claims add the same levels of acesulfame potassium and flavor.

The 40 mg/5 mL formulations

Claims 5 through 8 cover a suspension containing 40 mg of simvastatin per 5 mL. These claims increase both simethicone and sodium lauryl sulfate relative to the 20 mg formulation:

Simethicone: 2 mg/5 mL
Sodium lauryl sulfate: 0.10 mg/5 mL

The 40 mg claims again distinguish the formulations through methyl hydroxybenzoate at either 8 mg or 9 mg per 5 mL.

What is not expressly claimed?

The claims do not expressly cover:

Simvastatin tablets or capsules
Simvastatin solutions
Solid dispersions
Simvastatin suspensions using a different suspending system
Suspensions lacking magnesium aluminium silicate
Suspensions lacking carmellose sodium
Products using a different preservative system
Products containing 10 mg, 30 mg or another concentration per 5 mL
Products with a d90 above 20 micrometers
Products using a different surfactant instead of sodium lauryl sulfate
Products using a different sweetener or flavor system, unless the independent claim is otherwise met

The claims are composition claims. They do not expressly claim a manufacturing process, a method of treating hypercholesterolemia, a method of reducing cardiovascular risk, or a particular package or dosing device.

How do the claims compare with one another?

Claim group	Dose	Independent claim distinction	Dependent limitation
1-2	20 mg/5 mL	Methyl hydroxybenzoate at 8 mg; simethicone 1 mg; SLS 0.05 mg	Acesulfame potassium and flavor
3-4	20 mg/5 mL	Methyl hydroxybenzoate at 9 mg; simethicone 1 mg; SLS 0.05 mg	Acesulfame potassium and flavor
5-6	40 mg/5 mL	Methyl hydroxybenzoate at 8 mg; simethicone 2 mg; SLS 0.10 mg	Acesulfame potassium and flavor
7-8	40 mg/5 mL	Methyl hydroxybenzoate at 9 mg; simethicone 2 mg; SLS 0.10 mg	Acesulfame potassium and flavor

The dependent claims are commercially relevant because an oral liquid is commonly sweetened and flavored. They create additional claim positions but do not materially broaden the core formulation. A product that meets an independent claim and contains the added sweetener and flavor would potentially fall within both the independent claim and the dependent claim.

What are the strongest and weakest patent limitations?

Strongest limitations

The strongest practical limitations are:

The exact excipient combination
The 20 mg or 40 mg concentration
The d90 threshold of 20 micrometers or less
The combined use of magnesium aluminium silicate and carmellose sodium
The specified simethicone and sodium lauryl sulfate levels

These limitations create a relatively narrow formulation fingerprint. A commercial product that copies the full composition is easier to compare against the claims than a product that merely contains simvastatin in a liquid vehicle.

Weakest limitations

The principal vulnerability is likely prior art directed to:

Simvastatin oral suspensions
Micronized or finely milled simvastatin
Magnesium aluminium silicate suspensions
Carmellose-containing oral liquids
Paraben-preserved pharmaceutical suspensions
Simvastatin formulations using surfactants to improve wetting or dispersion

A validity challenge would likely focus on whether the claimed combination and particle-size limitation were obvious in light of earlier oral suspension technology. The commercial value of the claims depends on whether the specification provides evidence of an unexpected benefit, such as improved physical stability, dose uniformity, redispersibility, dissolution or palatability.

Exact numerical formulation claims can be difficult to attack solely because the ranges are narrow. A challenger would generally need to address the claimed combination, not just show that each excipient was individually known.

When does US Patent 9,597,289 lose exclusivity?

US Patent 9,597,289 issued on March 28, 2017. The patent’s enforceable term is generally calculated from the relevant U.S. nonprovisional or international filing date, subject to patent-term adjustment and any applicable terminal disclaimer. The issue date alone does not determine the expiration date.[1]

The statutory framework is:

Exclusivity component	Expected relevance
Patent term	Generally 20 years from the relevant effective filing date
Patent-term adjustment	May extend the term for USPTO examination delays
Patent-term extension	Typically associated with qualifying regulatory review and must be confirmed separately
Terminal disclaimer	Could shorten the term if the patent is tied to an earlier patent
Regulatory exclusivity	Depends on the approved NDA and FDA exclusivity records

A reliable expiration analysis requires the USPTO patent-term record rather than an issue-date calculation. Patent expiration should be checked against the USPTO Patent Center record and the FDA Orange Book, if the patent is listed for an approved product.[1,2]

What is the Orange Book status of US 9,597,289?

A patent number is not automatically an Orange Book patent. The FDA lists patents submitted by an NDA holder for an approved drug product when the patents meet the statutory listing categories, principally drug substance, drug product or method-of-use patents.[2]

The claims provided are drug-product formulation claims. They could be relevant to Orange Book listing if they were submitted for an approved NDA covering the corresponding simvastatin oral suspension. The claim text alone does not establish:

Whether the patent is listed in the Orange Book
The NDA associated with the patent
The listed patent-use code
Whether the listing covers 20 mg/5 mL, 40 mg/5 mL or both
Whether the listing has been withdrawn or delisted

For generic applicants, the critical regulatory issue is whether an ANDA must address the patent through a Paragraph IV certification or another certification category. The answer depends on the Orange Book listing and the proposed product’s labeling and formulation, not solely on the existence of the patent.[2,3]

Which companies are challenging the patent?

The claim text does not identify an ANDA filer, Paragraph IV notice, district-court action or settlement. Patent ownership and patent challenges are separate issues. A patent may remain unchallenged in reported litigation while still creating a formulation-design constraint for ANDA applicants.

A Paragraph IV challenge would require a generic applicant to assert that the patent is invalid, unenforceable or not infringed. A Paragraph IV notice also can trigger litigation by the NDA holder and, in qualifying circumstances, a 30-month stay of ANDA approval under the Hatch-Waxman framework.[3]

For this patent, a litigation assessment should distinguish:

Challenges to validity
Noninfringement positions based on particle size
Noninfringement positions based on excipient substitutions
Disputes over numerical ingredient amounts
Disputes over the meaning and measurement of d90
Whether the patent was listed for the proposed product

What generic entry risks exist for simvastatin oral suspension?

The principal launch scenarios are as follows.

Generic strategy	Infringement exposure	Technical or regulatory burden
Copy the claimed 20 mg/5 mL formula	High	Low formulation differentiation; high patent risk
Copy the 40 mg/5 mL formula	High	Same risk, with doubled simethicone and SLS
Change methyl hydroxybenzoate level	Potentially reduced	Must assess numerical claim construction and product performance
Replace magnesium aluminium silicate	Potentially reduced	Stability and suspension-performance development required
Replace carmellose sodium	Potentially reduced	May affect viscosity, settling and dose uniformity
Use simvastatin with d90 above 20 μm	Potentially reduced	Dissolution and physical stability risk
Change simethicone or SLS levels	Potentially reduced	May affect foam control and wetting
Use a different concentration	Potentially reduced	Labeling, dosing and bioequivalence implications

A formulation that omits one required element may avoid literal infringement, but the doctrine of equivalents could become relevant if the substituted component performs substantially the same function in substantially the same way with substantially the same result. Numerical limitations and particle-size requirements can make a doctrine-of-equivalents case fact-intensive.

Are biosimilar issues relevant?

No. Simvastatin is a chemically synthesized small-molecule drug. The relevant FDA pathway is generally an abbreviated new drug application for a generic product, not a 351(k) biosimilar application.[3,4]

The principal competitive questions are generic formulation design, bioequivalence, product quality and patent certification. Biosimilar interchangeability, reference biologics and patent dance procedures do not apply.

What manufacturing and IP barriers does the patent create?

The patent creates several development barriers even for a non-infringing product.

Particle engineering

The d90 limitation makes particle-size control a key manufacturing variable. Milling, micronization, classification, blending and sampling procedures may affect whether the API meets the claimed threshold.

Suspension stability

Magnesium aluminium silicate and carmellose sodium provide the formulation’s suspension structure. Changing either excipient may alter:

Sedimentation rate
Redispersibility
Viscosity
Dose uniformity
Pourability
Physical stability

Wetting and foam control

Sodium lauryl sulfate likely contributes to wetting and dispersion of hydrophobic simvastatin. Simethicone controls foam and may affect manufacturing and administration characteristics. Substitution can require new stability and performance studies.

Preservative system

Methyl, ethyl and propyl hydroxybenzoate levels are expressly claimed. A developer may avoid the listed numerical combinations by using a different preservative or concentration, but antimicrobial effectiveness, preservative content, palatability and regulatory acceptance must remain satisfactory.

How does this patent compare with the broader simvastatin patent landscape?

The patent occupies the formulation segment of the simvastatin estate.

Patent category	Relevance to this patent
Simvastatin compound patents	Generally separate and historically earlier
Solid oral dosage patents	Usually do not read on the claimed aqueous suspension
Oral liquid formulation patents	Closest technical and competitive category
Particle-size or micronization patents	Relevant to the d90 limitation and validity analysis
Manufacturing-process patents	May create separate freedom-to-operate barriers
Method-of-use patents	Not present in the claims provided
Packaging or dosing-device patents	Not present in the claims provided
Regulatory exclusivity	Depends on the approved NDA, not the patent claims alone

The commercial blocking position is therefore narrower than a compound patent but potentially meaningful for a liquid product that follows the claimed formulation architecture.

Key Takeaways

US Patent 9,597,289 claims a specific aqueous simvastatin suspension, not simvastatin generally.
All claims require simvastatin with d90 no greater than 20 micrometers.
Claims cover 20 mg/5 mL and 40 mg/5 mL formulations.
The principal formulation elements are magnesium aluminium silicate, carmellose sodium, propylene glycol, parabens, simethicone, sodium lauryl sulfate and a citrate-phosphate buffer.
Claims 2, 4, 6 and 8 add acesulfame potassium and flavor.
The best generic design-around opportunities involve particle size, suspending agents, preservatives, surfactant levels and concentration.
The patent does not contain an express method-of-use, manufacturing-process or biologic claim.
Orange Book listing, patent-term adjustment, NDA linkage and Paragraph IV activity must be established from FDA and USPTO records, not inferred from the claim text.
Biosimilar risk is not relevant because simvastatin is a small-molecule drug.

FAQs About US Patent 9,597,289

Does US 9,597,289 cover simvastatin tablets?

No. The claims are directed to an aqueous suspension suitable for oral administration. A conventional simvastatin tablet would not satisfy the suspension limitations.

Does a simvastatin suspension with d90 above 20 micrometers avoid the patent?

It may avoid literal infringement of the express particle-size limitation, but the complete formulation and measurement facts would control the analysis. The patent requires d90 of 20 micrometers or less.

Are the ingredient amounts approximate or exact?

The claims recite specific amounts per 5 mL. Whether a small deviation avoids infringement depends on claim construction, analytical tolerances, manufacturing variability and any applicable equivalents analysis.

Can a generic use a different sweetener?

Yes, the independent claims do not require acesulfame potassium or flavor. Those ingredients are required only by claims 2, 4, 6 and 8. A product could still infringe an independent claim if all of its other limitations are met.

Is a Paragraph IV certification required for every generic simvastatin product?

No. The certification obligation depends on the patent’s FDA listing, the proposed product, the relevant claims and the ANDA applicant’s legal position. A patent that is not listed, or a product that does not implicate the listed claims, may produce a different certification analysis.

References

United States Patent and Trademark Office. (n.d.). US Patent No. 9,597,289, Patent Center and patent-term information. U.S. Department of Commerce.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application submissions: Patent certifications and notice requirements.
U.S. Food and Drug Administration. (n.d.). Biosimilar and interchangeable biosimilar products.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Salerno Pharms	FLOLIPID	simvastatin	SUSPENSION;ORAL	206679-001	Apr 21, 2016		RX	Yes	No	⤷ Start Trial	⤷ Start Trial	Y				⤷ Start Trial
Salerno Pharms	FLOLIPID	simvastatin	SUSPENSION;ORAL	206679-002	Apr 21, 2016		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial	Y				⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

PCT Information
PCT Filed	April 26, 2007	PCT Application Number:	PCT/GB2007/001552
PCT Publication Date:	November 08, 2007	PCT Publication Number:	WO2007/125339

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	E552825	⤷ Start Trial
Australia	2007245410	⤷ Start Trial
China	101431982	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 9,597,289

Which drugs does patent 9,597,289 protect, and when does it expire?

Summary for Patent: 9,597,289