United States Patent RE43711: Levodopa Pulmonary Delivery Claims, Scope and Patent Landscape

U.S. Patent RE43,711 protects selected methods of treating Parkinson's disease by pulmonary administration of high-loading levodopa particles. Its core limitations are a levodopa content of at least about 90% by weight, low salt content, a non-reducing sugar or phospholipid excipient, and particle properties suitable for deep-lung delivery. Claims 11-24 add coordinated carbidopa administration and, in claims 12-14 and 24, a levodopa-DPPC-sodium chloride composition.

The patent is a method-of-treatment patent, not a composition claim standing alone. Infringement generally requires practicing the claimed administration steps, including pulmonary delivery and, for the combination claims, administration of carbidopa. The reissue patent cannot receive a new patent term merely because it was reissued. Its enforceability depends on the term of the original patent, any patent-term adjustment, terminal disclaimer, maintenance-fee status, and relevant litigation history. [1]

What does U.S. Patent RE43711 cover?

RE43,711 covers pulmonary treatment of Parkinson's disease using engineered levodopa particles. The claims divide into four principal groups.

Claim group	Core subject matter	Principal limitations
Claims 1-7	Pulmonary Parkinson's treatment	At least about 90 wt% levodopa, salt below 10 wt%, non-reducing sugar, pulmonary delivery
Claims 8-10	Specific levodopa-trehalose-sodium chloride delivery	At least about 90 wt% levodopa, no more than about 10 wt% trehalose, sodium chloride at about 3 wt% or less, simultaneous dispersion and inhalation
Claims 11-23	Levodopa plus carbidopa treatment	Pulmonary levodopa particles containing sodium chloride, with carbidopa administered before, after, or concurrently
Claim 24	Defined DPPC formulation and carbidopa	Levodopa:DPPC:sodium chloride ratio of about 90:8:2, pulmonary delivery, and carbidopa

The patent does not claim every inhaled levodopa product. A potentially infringing product must satisfy the relevant claim limitations, either literally or under the doctrine of equivalents where legally available.

How broad are the independent claims of RE43711?

Claims 1, 2, 8, 10, 11 and 24 are the principal independent claims. Their practical breadth differs substantially.

Claim 1: high-load levodopa particles

Claim 1 requires:

A Parkinson's disease patient.
Administration to the respiratory tract.
Particles containing about 90 wt% or more levodopa.
A salt below 10 wt%.
A non-reducing sugar.
Delivery to the pulmonary system.

The claim is relatively broad because it does not specify a particular salt, sugar, particle-size distribution, inhaler, dose, or carbidopa regimen. It may reach formulations using sugars other than trehalose, provided the sugar is legally characterized as non-reducing.

The claim has several limiting features. The formulation must contain both a salt and a non-reducing sugar. A formulation with 90% or more levodopa but no sugar would not satisfy the literal claim. A formulation using a reducing sugar would also raise a noninfringement position.

Claim 2: high-load, low-density respirable particles

Claim 2 adds physical particle requirements:

Tap density of about 0.4 g/cm³ or less.
Volume median geometric diameter of about 5 micrometers or more.
Aerodynamic diameter from about 1 to about 5 micrometers.
Particles consisting essentially of at least about 90 wt% levodopa, a non-reducing sugar and a salt below 10 wt%.

This is a narrower formulation and particle-engineering claim. The combination of a relatively large geometric diameter with a low aerodynamic diameter indicates low-density, highly porous particles. The claim is directed to particles that can have a large physical size for powder handling while maintaining an aerodynamic size suitable for pulmonary deposition.

Claims 3 and 4 divide the aerodynamic range into approximately 1-3 micrometers and 3-5 micrometers. Claims 5-7 narrow tap density to 0.3, 0.2 and 0.1 g/cm³ or less.

Claim 8: sodium chloride-specific formulation

Claim 8 substitutes sodium chloride for the broader salt limitation. It requires:

At least about 90 wt% levodopa.
Less than 10 wt% sodium chloride.
A non-reducing sugar.
Pulmonary delivery.

This claim is narrower in chemical scope than claim 1 but may be easier to apply to commercial formulations if sodium chloride is analytically present.

Claim 10: trehalose, low sodium chloride and simultaneous dispersion

Claim 10 requires:

At least about 90 wt% L-dopa.
About 10 wt% or less trehalose.
About 3 wt% or less sodium chloride.
A mass of particles in a receptacle.
Simultaneous dispersion and inhalation.
Administration to a human respiratory tract.

The receptacle and simultaneous-dispersion limitations create potential noninfringement positions for delivery systems that use a different powder-loading or inhalation sequence. The claim is more specific than claims 1 and 8 because it identifies trehalose, a sodium chloride ceiling, and a delivery operation.

Claims 11-24: carbidopa combination treatment

Claim 11 requires pulmonary levodopa particles containing sodium chloride and separate administration of carbidopa. The claim does not require a particular carbidopa route in its independent form. Claims 15 and 16 specify injection or oral administration, with claim 16 limited to oral administration.

Claims 21-23 cover temporal sequencing:

Carbidopa before levodopa.
Carbidopa after levodopa.
Carbidopa at the same time as levodopa.

Claim 17 adds oral levodopa. Claim 18 requires oral carbidopa in combination with oral levodopa.

These claims present a divided-infringement issue. A pulmonary levodopa manufacturer may not itself administer carbidopa. Liability analysis would depend on who performs the claimed steps, product labeling, instructions, inducement evidence, and the relationship among the manufacturer, prescriber and patient.

What formulation is specifically protected by claim 24?

Claim 24 identifies a formulation having an approximate weight ratio of:

Component	Approximate amount
Levodopa	90%
DPPC	8%
Sodium chloride	2%

DPPC is dipalmitoyl phosphatidylcholine, a pulmonary-surfactant-related phospholipid. The claim also requires pulmonary administration and carbidopa administration to the patient.

The phrase "about 90:8:2" creates a range rather than an exact mathematical requirement. Its construction would depend on the specification, prosecution history and ordinary meaning in the relevant formulation art. A formulation with materially different phospholipid or sodium chloride content could fall outside the literal ratio limitation.

Claim 24 is narrower than claims 11 and 12 because it requires DPPC and a defined ratio. It is also narrower than the broad high-levodopa claims because it does not cover all non-reducing sugars or all salts.

What particle properties matter under RE43711?

The patent uses both geometric and aerodynamic particle measurements.

Parameter	Claimed threshold or range	Practical relevance
Levodopa loading	About 90 wt% or more	Limits excipient burden and increases active-drug concentration
Salt content	Less than 10 wt% in several claims	Controls formulation composition
Sodium chloride	About 3 wt% or less in claim 10	Narrows the salt formulation
Tap density	About 0.4 g/cm³ or less	Indicates low-density particles
Narrower tap density	About 0.3, 0.2 or 0.1 g/cm³ or less	Creates progressively narrower dependent claims
Volume median geometric diameter	About 5 micrometers or more	Captures physically large porous particles
Aerodynamic diameter	About 1-5 micrometers	Targets respirable pulmonary deposition

Aerodynamic diameter is not interchangeable with geometric diameter. A particle can have a geometric diameter above 5 micrometers and still have an aerodynamic diameter in the 1-5 micrometer range if its density is sufficiently low. This distinction is central to infringement and validity analysis.

Measurement protocol can materially affect claim analysis. Parties would likely litigate the instrument, dispersion method, humidity, powder conditioning, sampling conditions and calculation method used to determine tap density, geometric diameter and aerodynamic diameter.

How strong is the patent estate represented by RE43711?

RE43,711 has meaningful conceptual coverage but uneven practical strength.

Strengths

The patent combines several commercially relevant features:

High levodopa loading.
Pulmonary delivery for rapid systemic exposure.
Low-density respirable particles.
Trehalose and sodium chloride embodiments.
DPPC-containing particles.
Use with carbidopa.
Timing relationships between carbidopa and levodopa.

Claims 1 and 8 are comparatively broad because they do not require the more demanding particle-density and aerodynamic-size limitations. Claims 2-7 are narrower but may align more closely with engineered dry-powder products.

Vulnerabilities

The principal validity risks are likely to involve:

Anticipation or obviousness based on earlier pulmonary drug-delivery patents.
Prior art describing levodopa inhalation or aerosol administration.
Prior art disclosing porous particles with low tap density.
Obviousness combinations involving trehalose, sodium chloride, phospholipids or DPPC.
Written-description and enablement challenges to broad "about 90%" and particle-property ranges.
Indefiniteness disputes over "about," "effective amount," "simultaneous dispersion and inhalation" and ratio ranges.
Double-patenting or terminal-disclaimer issues arising from related applications.

The unusual combination of a high geometric diameter and low aerodynamic diameter may support patentability if it was not taught in the cited prior art. The same limitation can narrow enforcement if a competing product uses denser or smaller particles.

When does RE43711 lose exclusivity?

The reissue patent's expiration is controlled by the original patent term, not by the reissue date. Under 35 U.S.C. § 251, reissue does not restart the patent term. For applications subject to the modern patent-term regime, the basic term is generally 20 years from the earliest effective nonprovisional U.S. filing date, subject to patent-term adjustment, terminal disclaimers and other statutory rules. [2]

The controlling status questions are:

Status issue	Relevance
Original patent and application	Establishes the term calculation
Earliest effective nonprovisional filing date	Usually controls the 20-year term
Patent-term adjustment	Can extend the term for qualifying USPTO delay
Terminal disclaimer	Can shorten the term to an earlier patent
Maintenance fees	Affects enforceability during the term
PTA or PTE	Must be verified in USPTO records
Reissue certificate	Shows the operative claims but does not reset term

A definitive expiration date must be taken from the USPTO Patent Center record for the original patent, the reissue record, the patent-term adjustment calculation and any terminal disclaimer. The claims supplied establish scope but do not establish those dates.

What is the Orange Book status of RE43711?

RE43,711 should not be treated as automatically listed in the FDA Orange Book merely because it covers inhaled levodopa. Orange Book listing is tied to an approved drug application and the patent information submitted by the NDA holder under FDA regulations. [3]

The relevant commercial product is Inbrija, an inhaled levodopa product approved by FDA in 2018 for intermittent treatment of off episodes in adults with Parkinson's disease treated with carbidopa/levodopa. The FDA label identifies inhaled levodopa capsules, the delivery device and the requirement that patients remain on their prescribed carbidopa/levodopa regimen. [4]

The current commercial patent analysis must therefore distinguish:

RE43,711 as a patent with the quoted claims.
FDA-listed patents for the Inbrija NDA.
Later continuation, divisional or improvement patents.
Patents covering the inhaler, capsule, formulation, dose, particle engineering or method of use.
Unlisted patents that may still be relevant to freedom to operate.

An Orange Book listing does not establish validity. It can, however, trigger Hatch-Waxman certification consequences for an ANDA applicant, including a potential Paragraph IV notice and litigation period. [5]

What Paragraph IV risks exist for an inhaled levodopa generic?

An ANDA applicant seeking approval for a product referencing an inhaled levodopa NDA would typically evaluate each listed patent and select an applicable certification. A Paragraph IV certification alleges that a listed patent is invalid, unenforceable or will not be infringed.

For RE43,711-type claims, an ANDA challenge could target:

Failure to meet the 90 wt% levodopa threshold.
Use of a reducing sugar or no sugar.
Sodium chloride above the claimed ceiling.
Absence of DPPC.
Different particle density.
Aerodynamic diameter outside the claimed range.
No simultaneous dispersion and inhalation.
No carbidopa administration by the generic manufacturer.
Lack of induced infringement by labeling.
Invalidity based on obviousness or anticipation.

A generic product using a different inhaler may still face method claims if its label instructs pulmonary administration of a formulation that satisfies the composition and particle limitations. Conversely, a product with a materially different excipient system or particle architecture may have a stronger noninfringement position.

Which companies challenge or compete with inhaled levodopa products?

The principal commercial reference product is Inbrija, developed through Civitas Pharmaceuticals and commercialized by Acorda Therapeutics. Merck acquired Acorda in 2020. [4,6]

The competitive field includes:

Company or category	Product or approach	Patent relevance
Merck/Acorda	Inbrija, inhaled levodopa	Reference product, inhaler, formulation and method claims
Generic drug manufacturers	Potential ANDA inhaled levodopa products	Paragraph IV and design-around risk
Oral levodopa manufacturers	Immediate- and extended-release carbidopa/levodopa	Therapeutic substitute, not necessarily a pulmonary patent competitor
Device and formulation developers	Dry-powder inhalers and engineered particles	May implicate device, particle and manufacturing patents
Investigational developers	Alternative inhaled or non-oral dopaminergic delivery	Competitive pressure without necessarily practicing RE43,711

Publicly identifiable challenge activity must be tied to a specific ANDA, Paragraph IV notice, FDA litigation listing or federal court docket. A general expectation of generic entry does not establish a legal challenge.

What manufacturing and IP barriers does RE43711 create?

The patent's technical barriers are concentrated in particle engineering and analytical reproducibility.

A competing manufacturer may need to control:

Levodopa loading at or above the claimed threshold.
Salt distribution and residual moisture.
Trehalose or another non-reducing sugar.
DPPC incorporation, if used.
Porosity and low tap density.
Geometric size and aerodynamic size simultaneously.
Powder deagglomeration during inhalation.
Capsule or receptacle discharge.
Consistent delivered dose.
Stability of levodopa against oxidation and degradation.

Manufacturing patents may be separate from RE43,711. A manufacturer can avoid this patent and still face blocking rights covering spray drying, particle formation, inhaler architecture, capsule design, dose metering, packaging or stability.

How does RE43711 compare with the Inbrija patent estate?

RE43,711 appears directed primarily to the therapeutic method and formulation architecture. The broader Inbrija estate may cover later-developed and more product-specific subject matter.

Issue	RE43,711	Later Inbrija-related patents
Claim type	Primarily method of treatment	May include formulation, device, dose and manufacturing claims
Active ingredient	Levodopa/L-Dopa	Levodopa
Pulmonary delivery	Required	Often required, depending on claim
Carbidopa	Central to claims 11-24	May be addressed differently
Particle limitations	Tap density, geometric and aerodynamic size	May use different or more product-specific parameters
Excipient scope	Salt, non-reducing sugar, DPPC	May specify particular excipients or ratios
Commercial relevance	Foundational scope	Potentially closer to marketed product
Term	Controlled by original patent term	Each patent has its own term and adjustments

A freedom-to-operate review should not stop at RE43,711. The decisive patents for an Inbrija-like product may be later patents that claim the marketed capsule strength, inhaler, powder composition or manufacturing process.

What generic launch scenarios exist?

Scenario 1: Paragraph IV challenge

A generic applicant challenges listed patents and argues invalidity or noninfringement. Litigation may delay approval under the Hatch-Waxman framework. The commercial launch date depends on litigation outcome, settlement terms, regulatory exclusivity and any remaining enforceable patents.

Scenario 2: Formulation design-around

A competitor uses a different sugar, avoids sodium chloride, changes DPPC content, or shifts particle density outside the claimed ranges. This approach must still account for continuation patents and equivalents risk.

Scenario 3: Device and labeling design-around

A competitor uses a different inhaler or delivery sequence. This may avoid claim 10's receptacle and simultaneous-dispersion limitations but would not necessarily avoid claims 1, 8 or 11.

Scenario 4: Post-expiration entry

If RE43,711 has expired and no later blocking patent applies, the patent itself should not prevent entry. FDA approval, product-specific patents, regulatory exclusivity, manufacturing capacity and commercial substitutability remain separate issues.

What is the revenue exposure associated with RE43711?

RE43,711's direct revenue exposure depends on whether its claims cover the marketed Inbrija formulation and whether the patent remains enforceable. The commercial exposure is greater where:

The marketed powder contains at least 90% levodopa.
Sodium chloride and a non-reducing sugar are present.
The particle measurements fall within claims 2-7.
The product uses DPPC near the 90:8:2 ratio.
Product labeling directs use with carbidopa.
No later patent provides a separate barrier after RE43,711 expires.

A patent can have substantial historical value even if its term has ended, because it may have supported earlier licensing, litigation or product-development strategy. Its current value is determined by enforceability and overlap with unexpired patents, not by the breadth of its original disclosure.

Key Takeaways

RE43,711 is directed to pulmonary treatment of Parkinson's disease using high-loading levodopa particles.
Claims 1 and 8 are the broadest practical formulation-method claims.
Claims 2-7 add low tap density and defined geometric and aerodynamic particle sizes.
Claim 10 focuses on trehalose, low sodium chloride content and simultaneous dispersion and inhalation.
Claims 11-24 require pulmonary levodopa with carbidopa administration; claim 24 specifies an approximate 90:8:2 levodopa-DPPC-sodium chloride ratio.
The patent claims methods, not a composition in isolation.
Reissue does not restart the patent term.
Orange Book status must be determined from the approved NDA's submitted patent information, not from the claim language alone.
Generic risk depends on the remaining term, listed patents, later continuation patents, product labeling and the ability to design around particle and excipient limitations.
The most important technical infringement issues are levodopa loading, salt content, sugar identity, DPPC content, tap density, aerodynamic diameter and carbidopa instructions.

FAQs

Does RE43711 cover oral carbidopa and inhaled levodopa used together?

Yes, claims 17 and 18 expressly address oral levodopa and oral carbidopa in combination with pulmonary levodopa treatment. Claim 16 separately specifies oral carbidopa.

Does a levodopa formulation with 89% levodopa infringe the 90% limitation?

It would not literally satisfy a strict 90 wt% limitation. The result could depend on how "about 90%" is construed and whether an equivalents theory is available.

Does changing trehalose to mannitol avoid RE43711?

It may avoid claims requiring trehalose, particularly claim 10, but it may not avoid claims that cover a broader non-reducing sugar category. The chemical classification of the substitute and the remaining claim limitations would control.

Can a generic avoid claims 11-24 by omitting carbidopa from its product?

Potentially, but the analysis depends on labeling and induced-infringement theories. Claims 11-24 require carbidopa administration to the patient, so a product label that does not direct or encourage carbidopa use may improve the noninfringement position.

Are DPPC-containing inhaled levodopa particles necessarily covered by claim 24?

No. Claim 24 requires an approximate levodopa:DPPC:sodium chloride ratio of 90:8:2, pulmonary levodopa administration and carbidopa administration. DPPC alone is not enough.

References

United States Patent and Trademark Office. (n.d.). U.S. Patent RE43,711, reissue patent record and claims. USPTO Patent Center.
United States Code. (2024). 35 U.S.C. §§ 154, 251. Office of the Law Revision Counsel.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
U.S. Food and Drug Administration. (2018). Inbrija (levodopa inhalation powder) prescribing information. FDA.
United States Code. (2024). 21 U.S.C. § 355(j). Office of the Law Revision Counsel.
Merck & Co., Inc. (2020). Merck completes acquisition of Acorda Therapeutics. Company transaction announcement.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Merz	INBRIJA	levodopa	POWDER;INHALATION	209184-001	Dec 21, 2018		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial				INTERMITTENT TREATMENT OF OFF EPISODES IN PATIENTS WITH PARKINSON'S DISEASE TREATED WITH CARBIDOPA/LEVODOPA BY INHALATION OF LEVODOPA POWDER PARTICLES	⤷ 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	2003218307	⤷ Start Trial
Canada	2478980	⤷ Start Trial
Cyprus	1118517	⤷ Start Trial
Denmark	1531798	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: RE43711

Which drugs does patent RE43711 protect, and when does it expire?

Summary for Patent: RE43711