United States Patent 9,901,640: Carbidopa-Levodopa Modified-Release Patent Scope and Competitive Landscape

US Patent 9,901,640 protects oral modified-release carbidopa-levodopa dosage forms that include a carboxylic acid, particularly tartaric acid, within defined molar-ratio ranges. The patent also covers multiparticulate, capsule, and sprinkle formats and dosing methods administered every six hours. Its principal commercial relevance is to extended-release carbidopa-levodopa products such as Rytary, although infringement depends on the full formulation, release profile, dosing regimen, and pharmacokinetic results.

The patent was issued on February 27, 2018. The supplied claims do not establish the patent’s current Orange Book status, terminal disclaimer, patent-term adjustment, patent-term extension, or litigation history. Those issues must be separated from the technical scope of the claims.

What invention does US Patent 9,901,640 protect?

The patent claims a modified-release oral dosage form containing four core components:

Carbidopa.
Levodopa.
A carboxylic acid.
A modified-release excipient.

Claim 1 adds two quantitative limitations:

The carboxylic acid-to-levodopa molar ratio is greater than 1:4 and less than 4:1.
Administration every six hours produces a levodopa peak-to-trough plasma-level ratio of about 1 to about 3.

The invention therefore is not limited to the chemical ingredients. It combines composition, release technology, dose interval, and pharmacokinetic performance. A product that contains carbidopa and levodopa with tartaric acid but does not satisfy the modified-release and pharmacokinetic limitations would not necessarily fall within claim 1.

The patent has two principal independent composition claims:

Claim	Core scope	Key distinction
1	Carbidopa, levodopa, carboxylic acid, modified-release excipient	Includes broad acid class, ratio, and q6h peak-to-trough limitation
15	Carbidopa, levodopa, tartaric acid, modified-release excipient	Narrows acid to tartaric acid but omits the explicit pharmacokinetic limitation

Claim 15 is commercially significant because it may be easier to prove against a formulation containing tartaric acid. Unlike claim 1, it does not expressly require a measured peak-to-trough ratio or administration every six hours in the composition claim.

How do the claims divide between composition and method protection?

Claims 1 through 11 and 15 through 22 cover dosage forms. Claims 12 through 14 and 23 through 25 cover therapeutic methods.

Composition claims

The composition claims cover:

Broad carboxylic-acid formulations under claim 1.
Tartaric-acid formulations under claim 15.
Delayed-release polymers under claims 7 and 18.
Enteric polymers under claims 8 and 19.
Multiparticulate dosage forms under claims 9 and 20.
Encapsulated multiparticulates under claims 10 and 21.
Sprinkle formulations for administration with food or liquids under claims 11 and 22.

The composition claims are layered. A formulation that falls outside a dependent claim may still infringe the corresponding independent claim.

Method claims

Claims 12 and 23 require administration of the claimed dosage form every six hours to alleviate at least one symptom of Parkinson’s disease.

Claims 13, 14, 24, and 25 narrow the pharmacokinetic result:

Peak-to-trough ratio of about 1 to about 2.5.
Maintenance from about one hour to about six hours after administration.
Further narrowing to about 1 to about 2.0.

These method claims create a potential enforcement issue. A method claim generally requires proof of the claimed administration schedule and therapeutic use. A product that is capable of being used every six hours may present a different infringement analysis from a product whose labeling specifically instructs q6h dosing.

What carboxylic acids are covered by the patent?

Claim 3 lists the following carboxylic acids:

Tartaric acid
Adipic acid
Succinic acid
Citric acid
Benzoic acid
Acetic acid
Ascorbic acid
Edetic acid
Fumaric acid
Lactic acid
Malic acid
Oleic acid
Sorbic acid
Stearic acid
Palmitic acid
Boric acid
Mixtures of those acids

Claim 4 narrows the formulation to tartaric acid.

The acid limitation is important because the patent does not claim only the active pharmaceutical ingredients. It claims a formulation architecture in which the acid is present at a specified molar relationship to levodopa and is released with carbidopa and levodopa through a modified-release system.

What ratio ranges are protected?

The ratio limitations are expressed as inequalities:

Claim	Carboxylic acid or tartaric acid-to-levodopa molar ratio
1, 15	Greater than 1:4 and less than 4:1
5, 16	Greater than 1:4 and less than 3:2
6, 17	Greater than 1:2 and less than 4:3

The most commercially important ranges are likely the narrower ranges in claims 6 and 17. They require a ratio above 0.5 and below approximately 1.333. A formulation at exactly 1:4, 3:2, 1:2, 4:3, or 4:1 would require separate analysis because the claims use "greater than" and "less than," rather than "at least" or "no more than."

The ratio is molar, not weight-based. A formulation assessment must convert the quantity of acid and levodopa into moles using the specific molecular forms used in the product, including any salt or hydrate implications.

What release technology is protected?

Claims 1 and 15 require a "modified release excipient" that provides modified release of carbidopa, levodopa, and the carboxylic acid.

Claims 7 and 18 specify a delayed-release polymer. Claims 8 and 19 further specify an enteric polymer.

This structure creates three levels of formulation coverage:

Any modified-release excipient meeting the independent claim.
A delayed-release polymer.
An enteric polymer.

The claims do not require a particular polymer by name. Potentially relevant excipient categories could include pH-dependent polymers, water-insoluble matrix polymers, film coatings, diffusion barriers, or other release-controlling materials, provided the claim’s functional limitations are met.

The functional wording creates two technical questions:

Whether the excipient must independently control release of all three components.
Whether release of the acid, carbidopa, and levodopa must occur over substantially the same period.

A design using separate release populations for each ingredient could present both infringement and claim-construction issues. The specification and prosecution history would be important in determining whether "provides for the modified release" requires a common release mechanism or merely a dosage form that produces modified release of each component.

How do the multiparticulate and sprinkle claims affect infringement risk?

Claims 9 through 11 and 20 through 22 target dosage-form implementation rather than only chemical composition.

The protected formats include:

Multiparticulates.
Encapsulated multiparticulates.
Sprinkle products administered with food or liquids.

These claims are commercially relevant because multiparticulate systems can contain separate coated particles with different release rates. A product may therefore infringe the composition claims even if it does not resemble a conventional monolithic extended-release tablet.

A capsule containing multiple coated beads is expressly within the dependent claims if the other limitations are met. A sprinkle formulation may also create labeling-based method risk if the product is directed to administration with food or liquids and the label instructs dosing every six hours.

The claims do not appear limited to capsules. A tablet, sachet, suspension, or other oral format could potentially fall within claim 1 or claim 15 if it satisfies the ingredient, excipient, ratio, and release limitations.

What is the technical significance of the peak-to-trough limitation?

The peak-to-trough limitation is a pharmacokinetic limitation. Claim 1 requires that q6h administration produce a levodopa plasma peak-to-trough ratio of about 1 to about 3. Claims 13, 14, 24, and 25 impose narrower ratios and time windows.

This limitation can operate in two ways:

It narrows the patent to formulations that produce relatively stable levodopa exposure.
It creates an evidentiary burden requiring pharmacokinetic testing or reliable clinical data.

A generic applicant could challenge the claims by arguing that the pharmacokinetic limitation is indefinite, not enabled across the full compositional scope, or not adequately supported by the specification. The patentee could respond that the limitation describes a measurable result obtained under a defined dosing regimen.

The term "about" introduces a range rather than a precise boundary. Its interpretation would likely depend on the specification, prosecution history, assay variability, and accepted pharmacokinetic practice. Peak-to-trough calculations also depend on sampling time, steady-state conditions, patient population, dose strength, and treatment interval.

How does US 9,901,640 compare with competing carbidopa-levodopa products?

Product or technology	Release profile	Carbidopa/levodopa	Relevance to US 9,901,640
Sinemet immediate release	Immediate release	Yes	Generally outside modified-release limitations
Sinemet CR	Controlled release	Yes	Could be relevant to modified-release claim analysis, but acid and ratio limitations remain critical
Rytary	Extended-release capsules with multiparticulate technology	Yes	Closest commercial technology category
Duopa	Continuous intestinal gel infusion	Yes	Generally outside the oral dosage-form claims
Inbrija	Inhaled levodopa	Levodopa only	Outside the claimed oral carbidopa-levodopa dosage form
Future oral generic ER product	Depends on formulation	Likely yes	Main Paragraph IV and design-around risk

Rytary is the most relevant commercial comparator because it is an oral extended-release carbidopa-levodopa product associated with multiparticulate delivery. The patent’s claims should not be treated as proof that every Rytary product attribute is covered by this patent. Commercial products are typically protected by multiple patents covering formulation, release characteristics, manufacturing, dosing, and therapeutic use.

What patents protect Rytary and related extended-release products?

The relevant patent estate is broader than US 9,901,640. Rytary and related IPX066 technology have been associated with patents covering:

Extended-release carbidopa-levodopa compositions.
Multiparticulate capsules.
Pharmacokinetic exposure.
Dosing regimens.
Manufacturing and coating processes.
Specific release profiles.
Method-of-use claims for Parkinson’s disease.

US 9,901,640 should therefore be analyzed as one layer of the estate rather than as the entire exclusivity position. The patent’s strongest apparent commercial positions are:

Tartaric-acid formulations.
Molar-ratio ranges around the claimed acid-to-levodopa window.
Multiparticulate or sprinkle implementations.
Q6h dosing that produces a low peak-to-trough ratio.

A freedom-to-operate review should map each Orange Book-listed patent against the proposed product’s ingredient ratios, coating materials, particle architecture, dissolution profile, dosing instructions, and pharmacokinetic data.

What is the Orange Book status and FDA exclusivity position?

The FDA Orange Book, rather than the patent document alone, determines whether a patent is listed against an approved small-molecule drug product. Orange Book listing can affect ANDA certification obligations and the timing of generic approval, but listing does not itself establish validity or infringement.[2]

The relevant regulatory questions are:

Whether US 9,901,640 is listed for an approved carbidopa-levodopa product.
Which strength, dosage form, and NDA are associated with the listing.
Whether the listing is active or has been delisted.
Whether the patent has a terminal disclaimer.
Whether pediatric exclusivity or patent-term extension affects the listed expiration date.
Whether the reference product’s labeling creates method-of-use implications.

The product’s FDA exclusivity and the patent term are separate. New chemical entity exclusivity is generally not the central issue for an established combination such as carbidopa-levodopa. Patent-based ANDA delay, any remaining regulatory exclusivity, and the listed patent expiration date must be reviewed independently.[2][3]

When does US 9,901,640 lose exclusivity?

The patent issued February 27, 2018. Its expiration cannot be calculated reliably from the claim text or issue date alone because the controlling date may depend on:

The earliest effective nonprovisional filing date.
Continuation or divisional relationships.
Patent-term adjustment.
Terminal disclaimers.
Patent-term extension.
Any applicable pediatric extension.

The legal expiration date should be taken from the USPTO patent record and the FDA Orange Book listing for the relevant reference product. A nominal 20-year calculation from the earliest nonprovisional filing date is only a starting point and is not a substitute for the official term calculation.[1][2]

Which companies are challenging the patent?

The supplied information does not identify any Paragraph IV notice letter, ANDA filer, district-court complaint, settlement agreement, or Federal Circuit decision involving US 9,901,640. The patent number and claims alone do not establish an active challenge.

For a generic applicant, the principal Paragraph IV theories would likely include:

Non-infringement based on omission of the claimed carboxylic acid.
A ratio outside the claimed ranges.
Use of a release excipient that does not provide the claimed release.
Failure to meet the peak-to-trough limitation.
Use of a non-oral, non-multiparticulate, or otherwise distinct dosage form.
Invalidity based on anticipation or obviousness.
Indefiniteness or lack of enablement for the pharmacokinetic limitations.

A Paragraph IV challenge would normally trigger a patent certification and could produce a 45-day period for the patent holder to bring infringement litigation, potentially resulting in a 30-month ANDA stay under the Hatch-Waxman framework.[3]

What generic launch risks exist?

At-risk launch

A generic applicant could launch before patent expiry only after prevailing in litigation, obtaining a favorable settlement, or accepting litigation risk. The highest risk would arise where the proposed product:

Uses tartaric acid.
Uses a ratio within 0.25 to 4.0.
Uses enteric-coated or delayed-release multiparticulates.
Is labeled for q6h administration.
Produces a peak-to-trough ratio near the claimed range.

Design-around launch

Potential design-around strategies include:

Removing the carboxylic acid.
Using an acid-to-levodopa ratio outside every asserted range.
Separating the acid from the modified-release population.
Using a release system that does not modified-release all three ingredients.
Developing a non-multiparticulate dosage form.
Using a dosing interval other than six hours, where method claims are material.
Producing a pharmacokinetic profile outside the claimed range.

Each design-around must account for other patents in the broader product estate. Avoiding US 9,901,640 may not avoid claims in related patents covering the same commercial platform.

How strong is the patent estate?

US 9,901,640 has meaningful claim breadth because it combines broad formulation language with narrower dependent claims. Claim 15 may be the most practical composition claim for a tartaric-acid product because it does not include the explicit peak-to-trough or q6h limitations.

The estate’s vulnerabilities are also identifiable:

The acid list is broad and may invite prior-art combinations.
Functional release language may create construction disputes.
Pharmacokinetic limitations may require complex proof.
The claims use "about" for key numerical results.
Ratio boundaries may be vulnerable to prior-art formulations near the claimed ranges.
The claims may depend heavily on specification support for the relationship between acid content, release rate, and levodopa exposure.

The patent is strongest against a product that copies the full formulation concept: tartaric acid, carbidopa, levodopa, delayed-release multiparticulates, and a q6h label producing relatively stable levodopa exposure.

Key Takeaways

US 9,901,640 claims oral modified-release carbidopa-levodopa formulations containing a carboxylic acid.
Tartaric acid is the most commercially important species in the claims.
The core ratio ranges are greater than 1:4 and less than 4:1, with narrower ranges of greater than 1:4 to less than 3:2 and greater than 1:2 to less than 4:3.
Claim 15 is a central composition claim because it requires tartaric acid but does not expressly require the claim 1 pharmacokinetic result.
Multiparticulate, encapsulated, and sprinkle formats are expressly covered by dependent claims.
The method claims require q6h administration and, in narrower claims, specified peak-to-trough levodopa ratios.
Rytary-type extended-release multiparticulate products are the closest commercial technology category.
Patent expiration must be confirmed from USPTO term data and the relevant Orange Book listing.
The supplied record does not establish current Paragraph IV litigation, settlement agreements, or active generic challengers.
A credible freedom-to-operate analysis must review the complete patent family and related patents, not US 9,901,640 alone.

FAQs About US Patent 9,901,640

Does US 9,901,640 cover immediate-release Sinemet?

No. The claims require an oral modified-release dosage form. Immediate-release carbidopa-levodopa products would generally lack the claimed modified-release limitation, although separate patents and product-specific facts would still require review.

Does a product infringe if it contains tartaric acid but uses a 1:10 tartaric-acid-to-levodopa ratio?

The ratio would fall outside the express range of greater than 1:4 and less than 4:1. Other claims and other patents could still be relevant.

Are enteric-coated beads required by every claim?

No. Enteric polymers appear only in dependent claims 8 and 19. The independent claims require a modified-release excipient but do not expressly require an enteric polymer.

Can a generic avoid the patent by using a tablet instead of a capsule?

Not necessarily. The independent composition claims are not limited to capsules. A tablet could still fall within the claims if it contains the required ingredients, ratio, modified-release excipient, and other limitations.

Does a low peak-to-trough ratio alone establish infringement?

No. For claim 1 and the method claims, the accused product must also satisfy the ingredient, release, ratio, dosage-form, and dosing limitations applicable to the asserted claim. A pharmacokinetic result alone is insufficient.

References

United States Patent and Trademark Office. (2018). U.S. Patent No. 9,901,640, Modified release dosage forms of carbidopa and levodopa.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (2024). Abbreviated new drug application submissions: Patent certifications and 30-month stays.
U.S. Food and Drug Administration. (2015). Rytary prescribing information.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Impax	RYTARY	carbidopa; levodopa	CAPSULE, EXTENDED RELEASE;ORAL	203312-001	Jan 7, 2015		RX	Yes	No	9,901,640	⤷ Start Trial	Y			TREATMENT OF PARKINSON'S DISEASE	⤷ Start Trial
Impax	RYTARY	carbidopa; levodopa	CAPSULE, EXTENDED RELEASE;ORAL	203312-002	Jan 7, 2015		RX	Yes	No	9,901,640	⤷ Start Trial	Y			TREATMENT OF PARKINSON'S DISEASE	⤷ Start Trial
Impax	RYTARY	carbidopa; levodopa	CAPSULE, EXTENDED RELEASE;ORAL	203312-003	Jan 7, 2015		RX	Yes	No	9,901,640	⤷ Start Trial	Y			TREATMENT OF PARKINSON'S DISEASE	⤷ Start Trial
Impax	RYTARY	carbidopa; levodopa	CAPSULE, EXTENDED RELEASE;ORAL	203312-004	Jan 7, 2015		RX	Yes	Yes	9,901,640	⤷ Start Trial	Y			TREATMENT OF PARKINSON'S DISEASE	⤷ 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

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2008343787	⤷ Start Trial
Canada	2711014	⤷ Start Trial
China	101910113	⤷ Start Trial
European Patent Office	2234963	⤷ Start Trial
Spain	2804348	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 9,901,640

Which drugs does patent 9,901,640 protect, and when does it expire?

Summary for Patent: 9,901,640