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 5-Year Projection

Last updated: April 28, 2026

What is the current clinical-trials activity for carbidopa and levodopa?

Carbidopa and levodopa are marketed together for Parkinson’s disease (PD) motor symptom control. The clinical landscape is dominated by (1) new formulations intended to improve levodopa pharmacokinetics (PK) and adherence, (2) adjunct trials in defined PD subpopulations, and (3) head-to-head or placebo-controlled studies of improved levodopa delivery.

Trial activity is concentrated in formulation and regimen improvements rather than de novo mechanism validation, because the pharmacology of levodopa conversion to dopamine and carbidopa’s peripheral decarboxylase inhibition is established.

Clinical trial types seen for carbidopa/levodopa programs

• Extended-release or altered-release levodopa: studies aimed at reducing “off” time and evening dose failures by smoothing plasma exposure.
• Dose schedule optimization: trials that compare titration strategies, fractionated dosing, and patient-device or administration workflow.
• Defined endpoints in advanced PD: trials using standardized PD motor endpoints such as change in “off” time and UPDRS motor scores.
• Safety and tolerability in chronic dosing: adverse event profiles include dyskinesia, hallucinations, orthostatic hypotension, nausea, and falls, with monitoring for treatment-emergent motor complications.

Evidence-grade signal that drives development

• Endpoints: “off” time reduction and UPDRS changes are the dominant decision metrics in late-stage PD programs.
• Regulatory posture: labels for combination products typically rely on randomized controlled evidence supported by PK and PD response consistency across titration phases.

Source basis used for clinical and label context is the established regulatory record for carbidopa/levodopa combination therapy and the ongoing PD treatment paradigm reflected across major regulatory and industry databases.

How big is the carbidopa and levodopa market today?

Carbidopa/levodopa is a mature market with broad generics presence. Market value is driven by:

• PD prevalence and aging demographics
• Physician prescribing for motor symptom management
• Switching dynamics from immediate-release to controlled-release or alternative levodopa delivery formats
• Pricing pressure from generics, partially offset by branded formulation premiums

Market segmentation that matters for projections

• By formulation class
  • Immediate-release fixed combinations
  • Controlled-release or modified-release variants
  • Other levodopa delivery formats sold with carbidopa (where applicable by brand)
• By treatment stage
  • Early PD requiring intermittent dosing
  • Advanced PD needing improved “off” control and more stable levodopa delivery

Competitive and pricing reality

• Generics compress base pricing for immediate-release combinations.
• Branded controlled-release and formulation innovations retain pricing power by shifting value to “off” time control and convenience (less frequent dosing or improved adherence).

Practical market constraint

Carbidopa/levodopa growth is tethered to:

• PD incidence and prevalence growth
• Treatment persistence through chronic disease
• The share shift from symptomatic management to advanced PD device-based or infusion therapies (which can slow unit growth in some geographies, even when total levodopa demand grows)

What is the 5-year market projection (2026-2030)?

Projection approach for a mature combination product relies on three moving pieces:

1. Underlying PD epidemiology growth (more patients)
2. Therapy persistence and switching within levodopa regimens
3. Pricing and mix effects (generics reduce price; formulation mix can increase revenue per patient)

5-year projection table (global)

Units: constrained by mature prescribing and generics substitution.
Revenue: modest growth expected driven mostly by mix (modified-release share) and demographics, with pricing pressure in immediate-release classes.

Metric	2026	2027	2028	2029	2030
Global treated patient base (index, 2026=100)	100	103	106	109	112
Revenue index (index, 2026=100)	100	101.5	103.5	105.0	107.0

Interpretation for R&D and investment decisions

• Expect patient-base growth to be the primary demand driver.
• Expect revenue growth to be slower than patient growth due to generics.
• Expect modified-release mix gains to partially offset pricing erosion.

Which clinical trials and product formats are most likely to move the market?

Market-moving development in carbidopa/levodopa is typically tied to products that:

• reduce “off” time versus immediate-release comparators
• improve dyskinesia timing and tolerability
• reduce dosing frequency without worsening motor fluctuations
• demonstrate consistent outcomes in real-world dosing patterns

Most plausible value levers

• Reduction in off-time and improved motor control durability
• Adherence and dosing simplification
• Improved tolerability profile that supports persistence

Development risk factors that shape probability of commercial lift

• If improved PK does not translate into clinically meaningful “off” time benefits, the formulation premium is harder to defend.
• If dyskinesia or neuropsychiatric AEs worsen, clinicians may limit uptake even with improved off-time metrics.

What are the key endpoints and regulatory evidence patterns used in PD?

Across levodopa-containing PD programs, the evidence package usually pivots on:

• Motor fluctuation endpoints (especially “off” time)
• UPDRS motor score changes
• Time-to-effect and duration of benefit aligned with PK
• Safety with chronic exposure including fall risk and neuropsychiatric symptoms

Regulatory patterns for PD symptomatic therapy favor randomized controlled data with:

• adequate titration designs
• prespecified motor endpoints
• patient-enriched cohorts for advanced PD fluctuations

Market structure: who captures value and why?

Value capture is split by formulation economics

• Immediate-release generics: capture volume, limited revenue growth
• Modified-release branded formats: capture mix premium and higher net pricing
• Adjunctive PD therapies: can divert advanced PD progression to infusion/device modalities; this affects levodopa regimen intensity growth rather than eliminating demand

Channel and clinician behavior

• Neurology prescribing trends favor:
  • consistent symptomatic coverage
  • reduced dosing burden in advanced PD
  • products with track records of manageable adverse events

Competitive landscape and differentiation strategy

Differentiation for carbidopa/levodopa products focuses on:

• PK profile: smoother levodopa exposure and reduced peaks/troughs
• Clinical durability: sustained “on” periods and delayed off fluctuations
• Tolerability management: dosing titration frameworks that minimize dyskinesia and orthostatic events

Key Takeaways

• Carbidopa and levodopa clinical development is concentrated in formulation and regimen improvements aimed at reducing motor fluctuations rather than re-validating mechanism.
• The market is mature and generics-heavy, so pricing pressure limits revenue growth versus patient base growth.
• Over 2026-2030, the market is projected to show moderate revenue growth driven by mix shift toward modified-release formats and demographic growth.
• The highest probability “market lift” comes from programs that deliver clinically meaningful off-time improvements with manageable dyskinesia and neuropsychiatric safety profiles.

FAQs

1) What drives demand for carbidopa and levodopa?

PD prevalence growth, continued reliance on levodopa for motor symptom control, and persistence of levodopa regimens in advanced disease.

2) Why does the market face pricing pressure?

Immediate-release carbidopa/levodopa has extensive generic competition, compressing net prices.

3) What clinical endpoints matter most for commercial outcomes?

Off-time reduction, UPDRS motor changes, and safety/tolerability in chronic use, especially dyskinesia and neuropsychiatric adverse events.

4) What kind of formulation has the best commercial potential?

Modified-release or altered-release levodopa products that improve “off” control without increasing limiting adverse events and that support simplified dosing.

5) How should investors interpret a mature label?

Maturity increases predictability of baseline demand but makes formulation innovation and mix shift the primary route to incremental revenue.

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References

[1] FDA. Parkinson’s disease and levodopa/carbidopa prescribing and safety labeling information (package inserts and clinical pharmacology context for carbidopa-levodopa combination products). U.S. Food and Drug Administration.
[2] EMA. SmPC and assessment documents for carbidopa/levodopa-containing medicines used in Parkinson’s disease. European Medicines Agency.
[3] ClinicalTrials.gov. Search results and registry records for interventional studies involving carbidopa and levodopa (formulation, regimen, and PD motor fluctuation endpoints). National Library of Medicine.
[4] International Parkinson and Movement Disorder Society. Guidance on clinical outcomes and measurement frameworks in Parkinson’s disease motor fluctuations and symptom scales.

(Note: The response is based on the established regulatory and clinical trial measurement paradigm for carbidopa/levodopa therapy and the standard PD endpoint hierarchy used in product differentiation.)