CLINICAL TRIALS PROFILE FOR CARBIDOPA AND LEVODOPA

505(b)(2) Clinical Trials for CARBIDOPA AND LEVODOPA

This table shows clinical trials for potential 505(b)(2) applications. See the next table for all clinical trials

Trial Type	Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
New Formulation	NCT00640159 ↗	Tolerability and Efficacy of Switch From Oral Selegiline to Orally Disintegrating Selegiline (Zelapar) in Patients With Parkinson's Disease	Completed	Baylor College of Medicine	Phase 4	2007-01-01	Parkinson's disease (PD) is a progressive neurodegenerative disease. Symptomatic therapy is primarily aimed at restoring dopamine function in the brain. Oral selegiline in conjunction with L-dopa has been a mainstay of therapy for PD patients experiencing motor fluctuations for many years. The mechanisms accounting for selegiline's beneficial adjunctive action in the treatment of PD are not fully understood. Inhibition of monoamine oxidase (MAO) type B (MAO-B) activity is generally considered to be of primary importance. Oral selegiline has low bio-availability and is typically dosed BID, for a total of 5-10 mg daily. Recently, the FDA approved a new orally disintegration tablet (ODT) formulation of selegiline, called ZelaparTM. This new formulation utilizes Zydis technology to dissolve in the mouth, with absorption through the oral mucosa, thereby largely bypassing the gut and avoiding first pass hepatic metabolism. This allows more active drug to be delivered at a lower dose. Consequently, Zelapar is dosed once-daily, up to 2.5 mg per day. There are no empirical data indicating whether the use of the new approved formulation of selegiline ODT (Zelapar) is superior or preferred by patients compared to traditional oral selegiline. It is believed that clinical efficacy will be preserved or enhanced, by delivering more active drug, with improved patient preference for the ODT formulation due to the once-daily dosing . The effectiveness of orally disintegrating selegiline as an adjunct to carbidopa/levodopa in the treatment of PD was established in a multicenter randomized placebo-controlled trial (n=140; 94 received orally disintegrating selegiline, 46 received placebo) of three months' duration. Patients randomized to orally disintegrating selegiline received a daily dose of 1.25 mg for the first 6 weeks and a daily dose of 2.5 mg for the last 6 weeks. Patients were all treated with levodopa and could additionally have been on dopamine agonists, anticholinergics, amantadine, or any combination of these during the trial. At 12 weeks, orally disintegrating selegiline-treated patients had an average of 2.2 hours per day less "OFF" time compared to baseline. Placebo treated patients had 0.6 hours per day less "OFF" time compared to baseline. These differences were significant (p < 0.001). Adverse events were very similar between drug and placebo.
New Combination	NCT01766258 ↗	Efficacy and Safety Proof of Concept Study in Patients With Parkinson's Disease and End-of-dose Motor Fluctuations	Completed	Orion Corporation, Orion Pharma	Phase 2	2011-05-01	The primary objective of the study is to assess the efficacy, carbidopa dose response and safety of ODM-101, a new combination of levodopa, carbidopa and entacapone in the treatment of Parkinson's disease (PD) patients with end-of-dose motor fluctuations.

All Clinical Trials for CARBIDOPA AND LEVODOPA

Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
NCT00086294 ↗	ACP-103 to Treat Parkinson's Disease	Completed	National Institute of Neurological Disorders and Stroke (NINDS)	Phase 2	2004-06-25	This study will evaluate the effects of an experimental drug called ACP-103 on Parkinson's disease symptoms and on dyskinesias (involuntary movements) that develop as a result of long-term levodopa treatment. ACP-103 changes the spread of certain brain signals that are affected in patients with Parkinson's disease. Patients with relatively advanced Parkinson's disease and dyskinesias who are between 30 and 80 years of age may be eligible for this study. Candidates are screened with a complete medical history and physical examination, neurological evaluation, blood and urine tests, and electrocardiogram (ECG). A brain magnetic resonance imaging (MRI) scan, CT scan, and chest x-ray may be done if medically indicated. Patients enrolled in the study will, if possible, stop taking all antiparkinsonian medications for one month (2 months for Selegiline) before the study begins and throughout its duration. Exceptions are Sinemet (levodopa/carbidopa), Mirapex (pramipexole) and Requip (ropinirole). Levodopa Dose Finding After the screening evaluations, patients are admitted to the NIH Clinical Center for 2 to 3 days to undergo a levodopa "dose-finding" procedure. For this test, patients stop taking Sinemet and instead have levodopa infused through a vein. During the infusion, the drug dose is increased slowly until either 1) parkinsonian symptoms improve, 2) unacceptable side effects occur, or 3) the maximum study dose is reached. Side effects are monitored closely during the infusions, and parkinsonian symptoms are evaluated frequently during and after the infusions. The infusions usually begin early in the morning and continue until evening. Once the infusion is finished, patients resume taking their regular oral Sinemet dose. The infusions are repeated once a week during 1-day inpatient evaluations. Treatment Patients are randomly assigned to take either ACP-103 followed by placebo (a look-alike pill with no active ingredient) once a week for 10 weeks or vice versa (placebo followed by ACP-103). Patients are admitted to the Clinical Center for each dose. During this admission they have a brief medical examination, blood and urine tests, ECG, and review of symptoms or changes in their condition. They also have an infusion of levodopa (see above) at the previously determined optimal rate. Parkinsonism symptoms and dyskinesias are evaluated every 30 minutes for about 6 hours. At the end of the infusions and ratings, patients are discharged home with their regular Parkinson's medications until the following visit. Two weeks after their final dose of ACP-103 or placebo, patients are contact by telephone for a follow-up safety check. At that time, the investigator may ask the patient to return to the clinic for closer evaluation.
NCT00099268 ↗	Efficacy and Safety of Carbidopa/Levodopa/Entacapone in Patients With Parkinson's Disease Requiring Initiation of Levodopa Therapy	Completed	Orion Corporation, Orion Pharma	Phase 3	2004-09-01	The CELC200A2401 study has been designed in order to evaluate the hypothesis that administering the combination carbidopa/levodopa/entacapone at the time that levodopa therapy is initiated results in a decrease in the risk of the development of motor complications for patients with Parkinson's disease.
NCT00099268 ↗	Efficacy and Safety of Carbidopa/Levodopa/Entacapone in Patients With Parkinson's Disease Requiring Initiation of Levodopa Therapy	Completed	Novartis Pharmaceuticals	Phase 3	2004-09-01	The CELC200A2401 study has been designed in order to evaluate the hypothesis that administering the combination carbidopa/levodopa/entacapone at the time that levodopa therapy is initiated results in a decrease in the risk of the development of motor complications for patients with Parkinson's disease.

Clinical Trial Conditions for CARBIDOPA AND LEVODOPA

Condition Name

Condition Name for CARBIDOPA AND LEVODOPA
Intervention	Trials
Parkinson's Disease	72
Parkinson Disease	39
Advanced Parkinson's Disease	9

Condition MeSH

Condition MeSH for CARBIDOPA AND LEVODOPA
Intervention	Trials
Parkinson Disease	141
Depression	7
Dyskinesias	7

Clinical Trial Locations for CARBIDOPA AND LEVODOPA

Trials by Country

Trials by Country for CARBIDOPA AND LEVODOPA
Location	Trials
United States	565
Italy	42
Canada	40
Germany	39
Spain	33

Trials by US State

Trials by US State for CARBIDOPA AND LEVODOPA
Location	Trials
California	39
Florida	35
New York	30
Illinois	30
Texas	29

Clinical Trial Progress for CARBIDOPA AND LEVODOPA

Clinical Trial Phase

Clinical Trial Phase for CARBIDOPA AND LEVODOPA
Clinical Trial Phase	Trials
PHASE4	3
PHASE2	1
PHASE1	2

Clinical Trial Status

Clinical Trial Status for CARBIDOPA AND LEVODOPA
Clinical Trial Phase	Trials
Completed	132
Recruiting	18
Not yet recruiting	12

Clinical Trial Sponsors for CARBIDOPA AND LEVODOPA

Sponsor Name

Sponsor Name for CARBIDOPA AND LEVODOPA
Sponsor	Trials
Bial - Portela C S.A.	13
Impax Laboratories, LLC	13
IMPAX Laboratories, Inc.	12

Sponsor Type

Sponsor Type for CARBIDOPA AND LEVODOPA
Sponsor	Trials
Industry	163
Other	122
NIH	19

Carbidopa and Levodopa Clinical Trials Update, Market Analysis, and Pricing/Exclusivity Projections (2026)

Last updated: July 28, 2026

Carbidopa and levodopa is a mature Parkinson’s disease (PD) portfolio with broad, long-standing generic access in the US and multiple global branded and authorized generic products. Clinical-trials activity is dominated by formulation changes, delivery technologies (including intestinal gel and extended-release strategies), and adjunct trials aimed at optimizing “motor complications” management. Market growth is constrained by generic penetration, but total addressable PD volume and ongoing uptake of combination regimens continues to add incremental demand.

What clinical trials are ongoing for carbidopa and levodopa in 2024–2026?

Active and recent clinical-trials work is concentrated in three buckets: (1) new levodopa release profiles, (2) device-assisted delivery, and (3) comparative effectiveness for advanced PD phenotypes. Trials typically enroll PD patients with motor fluctuations and dyskinesias and evaluate changes in off-time, ON time without troublesome dyskinesia, and tolerability.

Which trial designs are most common for levodopa formulations

Common endpoints across levodopa program updates include:

• Off-time reduction (hours per day)
• ON-time improvement (with and without dyskinesia)
• Dyskinesia severity scores
• Treatment-emergent adverse events (orthostatic hypotension, nausea, hallucinations)
• Pharmacokinetic measures (Cmax, Tmax, AUC) for release-profile comparisons

Key subpopulations in current studies

Trials often target:

• Early PD patients to evaluate dose titration and consistency of response
• Advanced PD patients with wearing-off and dyskinesias
• Patients switching between immediate-release and extended-release strategies
• Patients requiring enteral delivery or those with adherence issues

Where trials are concentrated geographically

Enrollment tends to reflect global PD trial networks, with North America and Europe as core sites. Emerging trial sites also appear in Asia-Pacific for formulation and comparative pharmacology studies.

Which carbidopa–levodopa products are driving the market and why?

The market is split between immediate-release generic tablets, extended-release and orally disintegrating/alternative solid forms, and device-assisted delivery (notably intestinal gel products in advanced PD). Brand value sits primarily in differentiated delivery and adherence solutions, not in basic levodopa efficacy.

Market demand drivers

• Rising diagnosed PD prevalence and aging demographics
• Continued long-term levodopa use as standard-of-care
• Patient and physician preference for reduced dosing frequency and smoother levodopa exposure in motor fluctuations
• Use of adjunct therapies and “optimization” of levodopa dosing schedules

Market constraints

• High generic penetration in immediate-release carbidopa/levodopa
• Patent estate aging for many classic actives and first-wave formulations
• Ongoing pricing pressure in public and private formularies
• Off-formulary barriers for small molecule cost-containment policies

How does carbidopa and levodopa compare with other Parkinson’s drugs on growth and lifecycle?

Carbidopa–levodopa is not a typical “high-growth” drug in the patent sense. It is a volume product with long-cycle demand and frequent use across the disease course. Compared with dopamine agonists, MAO-B inhibitors, COMT inhibitors, and novel pipeline MOAs, levodopa’s growth is more directly tied to diagnosis and dosing intensity than to breakthrough therapeutic shifts.

Competitive dynamics by class

• Against dopamine agonists: levodopa remains the anchor therapy due to efficacy in motor control, with agonists used more for early-stage or adjunct purposes.
• Against MAO-B/COMT adjuncts: those add-ons can delay levodopa escalation but do not eliminate levodopa need.
• Against advanced PD infusion therapies: intestinal and device-delivered strategies can reduce motor fluctuations; however, they compete against each other for a narrower advanced-patient segment.

When do carbidopa and levodopa formulations lose exclusivity in the US?

Exclusivity is now mostly formulation- and product-specific rather than active-ingredient specific. For immediate-release carbidopa/levodopa, generic availability is longstanding, so US exclusivity effects are limited to specific NDCs (strength/form/label) and any later-introduced extended-release or novel delivery claims.

How to interpret exclusivity risk for levo/carbidopa products

For market projection and generic entry planning, the key question is not active ingredient expiration, but:

• Whether a given NDC still has listed Orange Book patents
• Whether those patents cover formulation, method-of-use, or manufacturing/impurity profiles
• Whether the product has a “listed” FDA exclusivity event still in force

Actionable projection framing

• Near-term (1–3 years): incremental share shifts among authorized generics, wholesalers, and pharmacy benefit manager contracts; limited “new” share from true brand exclusivity for immediate-release products.
• Mid-term (3–7 years): growth or share protection depends on whether differentiated delivery/ER products retain enforceable listed patents and whether payers favor those claims.
• Long-term (7–10 years): further erosion in any remaining differentiated categories unless new patentable improvements emerge.

What is the Orange Book status of carbidopa and levodopa products?

Carbidopa/levodopa has extensive historical Orange Book listings for multiple brand and later-filed generics or follow-on products. For actionable freedom-to-operate (FTO) or generic launch risk, market participants must map specific NDC(s) to:

• Listed patents (composition, formulation, method-of-use, device/delivery system where applicable)
• Patent expiration dates
• Any FDA exclusivity blocks (if applicable)
• Whether Paragraph IV certifications have already been litigated for those exact patents

Why Orange Book mapping matters for market projection

Pricing and share are influenced by which NDCs still have enforceable protection. Even if the active ingredient is off-patent, listed patents on release profile or device-related methods can support continued branded economics.

What patents protect carbidopa and levodopa formulations, and how strong is the estate?

Patent coverage for carbidopa and levodopa typically falls into:

• Controlled-release or extended-release formulation claims
• Specific dose forms (tablet coatings, polymer systems, disintegrating/alternative solids)
• Manufacturing methods and impurity limits
• Method-of-use claims that describe specific dosing regimens or patient populations (less common for basic levodopa schedules in later years, but present for some follow-on strategies)

Patent estate strength assessment (business lens)

For a mature asset, “strength” usually translates into:

• Number of listed patents per NDC
• Remaining term on the last-to-expire formulation or method-of-use patent
• Litigation history tied to those patents
• Whether entrants used design-arounds that successfully avoided infringement

How do Paragraph IV challenges affect carbidopa and levodopa market pricing?

Paragraph IV litigation has historically accelerated generic penetration where Orange Book listed patents are successfully attacked or where settlements allow earlier entry for specified strengths/forms. In a mature market like carbidopa/levodopa, the primary impacts are:

• Rapid price compression in the affected NDC category
• Short-lived premium for differentiated delivery forms post-licensing or post-landing of authorized generics
• Contracting changes by PBMs after entry

Settlement effect on market projection

Where settlements exist, generic entry often follows a defined timeline and is limited to specific strengths or dosage forms, which means market share gains can be uneven across the portfolio.

What generic entry risks exist for carbidopa and levodopa products?

Generic entry risks depend on NDC-level protection:

• Formulation/ER products: higher risk of non-infringement or method-of-use barriers if patents are still active.
• Immediate-release tablets: lower risk; genericization is already established, leaving only “brand-to-generic switching” rather than first generic entry.
• Device-associated categories: risk increases due to system-level claims and method claims tied to administration.

Manufacturing and formulation barriers

Even for generics, levodopa stability, release kinetics, and bioequivalence can drive:

• Higher development and validation cost
• Longer time-to-market for particular release mechanisms
• Increased likelihood of litigation where formulation changes affect dissolution profiles

What is the clinical safety and tolerability outlook for levodopa regimens under current trials?

Across the class, the consistent adverse-event profile includes:

• Orthostatic hypotension
• Dyskinesia with long-term use
• Nausea and GI effects
• Hallucinations and psychosis risk, especially in older and cognitively impaired patients
• Sleep disturbances and impulse-control symptoms in some regimens

Trial updates typically emphasize:

• Dose titration strategies
• Minimization of off-time while managing dyskinesia risk
• Reduced peak-trough variability via ER or alternative delivery systems

Market projection for carbidopa and levodopa to 2030: how to model demand and revenue?

Because the active ingredient is mature and widely genericized, “market projection” should be modeled as:

• Volume growth driven by PD prevalence and treatment adherence
• Mix shift between immediate-release generics and differentiated ER/device categories
• Price erosion across immediate-release strengths after periodic contract renegotiations
• Limited incremental value from new entrants only where NDC-level patents or exclusivity still exist

Base-case projection logic (for investment and licensing planning)

• Core demand persists at scale due to levodopa’s central role across PD.
• Revenue growth is mostly mix-driven rather than net-new mechanism-driven.
• Any meaningful uplift comes from differentiated delivery categories that reduce motor complications and from favorable payer outcomes that support premium pricing.

Scenario framework

• Downside: further accelerated generic contracting and substitution in ER categories; increased payer restrictions.
• Base: stable disease incidence and diagnosis rates plus gradual mix shift to smoother-release strategies.
• Upside: durable differentiation in device-associated or ER categories due to patent staying power and demonstrated outcomes in motor complications, paired with contracting that supports premium.

Commercial landscape: which companies are positioned in the near term?

Commercially, the field is dominated by:

• Generic manufacturers supplying immediate-release carbidopa/levodopa and authorized generics
• Select branded or specialty companies with differentiated delivery products aimed at advanced PD
• Companies licensing improvements in formulation technology or delivery systems

The near-term advantage is less about basic levodopa patents and more about:

• Access to differentiated product platforms
• Contracting strength in major formularies
• Ability to defend or design-around NDC-level listed patents

Key regulatory and reimbursement factors shaping adoption

FDA pathway dynamics

Carbidopa/levodopa products largely move through ANDA pathways once bioequivalence requirements are met and listed patents expire. For differentiated delivery forms, regulatory focus centers on:

• Product-specific release and PK similarity
• Device-related labeling constraints (where applicable)
• Labeling claims tied to patient populations and motor complication outcomes

Reimbursement

Reimbursement is influenced by:

• Step therapy or prior authorization for ER/device products
• Preferred drug lists for immediate-release generics
• Comparative value perceptions among payers for off-time reduction and reduced complications

Key Takeaways

• Clinical-trials activity for carbidopa and levodopa in 2024–2026 is dominated by formulation and delivery optimization aimed at reducing motor fluctuations and dyskinesia burden.
• Market growth is constrained by extensive generic penetration in immediate-release carbidopa/levodopa. Revenue outlook depends on mix into differentiated ER and advanced delivery categories.
• Exclusivity and patent leverage are primarily NDC-specific (formulation, method-of-use, manufacturing, and delivery-related claims), not active ingredient class-level protection.
• Generic entry risk is highest for any differentiated NDCs that still carry enforceable Orange Book patents; otherwise, near-term share shifts are mostly contracting-driven rather than entry-driven.
• Projection to 2030 should be modeled through prevalence-driven volume growth, continued price erosion in core generics, and premium persistence only where differentiated products retain enforceable patent/label leverage.

FAQs

1. Which endpoints do trials use to compare extended-release vs immediate-release carbidopa/levodopa in advanced Parkinson’s disease?
2. How do Orange Book-listed formulation patents influence ANDA timing for carbidopa/levodopa strengths and dosage forms?
3. What is the most common reason for switching from immediate-release carbidopa/levodopa to ER or device-assisted regimens?
4. Do carbidopa/levodopa generics face bioequivalence challenges due to levodopa release kinetics and dissolution profiles?
5. How does reimbursement design (formulary tiering and step therapy) impact uptake of premium levodopa formulations?

References

No sources were cited because no external clinical-trials, FDA, Orange Book, or patent-lists data were provided in the prompt.