Last Updated: May 4, 2026

CLINICAL TRIALS PROFILE FOR CARBIDOPA


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505(b)(2) Clinical Trials for CARBIDOPA

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.
>Trial Type >Trial ID >Title >Status >Phase >Start Date >Summary

All Clinical Trials for CARBIDOPA

Trial ID Title Status Sponsor Phase Start Date Summary
NCT00028106 ↗ 131MIBG to Treat Malignant Pheochromocytoma Completed Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Phase 2 2001-12-05 This study will evaluate the effectiveness of 131MIBG in treating malignant pheochromocytoma and whether sensitization medications improve the response to treatment. Pheochromocytoma is a rare type of tumor that usually occurs in the adrenal glands. The tumor cells release chemicals like adrenaline that can cause large increases in blood pressure and pulse rate, with serious health consequences. Tumor in the adrenal glands usually can be removed surgically, but if the pheochromocytoma is malignant-i.e., has spread to many sites in the body-or is located in places where surgery is difficult or impossible, no satisfactory treatment is available. 131MIBG is a combination of an adrenaline-like chemical and a radioactive form of iodine. The 131MIBG attaches to the tumor cells and the high concentration of radioactive iodine kills them. Previous studies using 131MIBG to treat pheochromocytoma had a 36% response rate in terms of complete or partial improvement. This study will examine whether adding other sensitization medications to the 131MIBG treatment regimen will enhance its effectiveness in reducing the size and number of tumors. Patients 18 years of age and older with malignant or inoperable pheochromocytoma may be eligible for this 18-month study. Candidates will be screened with various tests and procedures, which may include a medical history, physical examination, blood and urine tests, lung function studies, electrocardiogram, echocardiogram, computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and bone scans and other scans using radioactive MIBG and octreotide. Participants will be randomly assigned to one of two treatment groups: 1) 131MIBG plus sensitization medications, or 2) 131MIBG alone. All patients will be hospitalized 3 to 5 days for each 131MIBG treatment. The drug will be infused through a vein (intravenously, or I.V.) over 10 to 30 minutes. Patients will receive up to 3 treatments, separated by at least 3 months. All patients will also take potassium to protect the thyroid gland from radioactive iodine generated by the 131MIBG. The potassium is taken twice a day for 30 days, beginning the day before the 131MIBG treatment. Patients in the sensitization group will receive the following additional drugs for sensitization: methylprednisolone, intravenously a few minutes before 131MIBG treatment; Roaccutan, by mouth (capsules) twice a day for 6 weeks before treatment; Demser, by mouth 3 times a week for 1 week before treatment, and Carbidopa, by mouth every 6 hours for 4 days before treatment. After each treatment, patients will have a clinical evaluation and periodic blood tests to check for adverse side effects of radiotherapy. Follow-up visits at NIH will be scheduled at 12 and 18 months after the first 131MIBG treatment for clinical, laboratory and imaging tests. Patients who had tumors in the lungs before treatment will have lung function tests 1, 3, and 6 months after each treatment. CT, MRI 131MIBG, and PET scanning will be done 1 week before each treatment. Patients who have tumors that have grown by more than 25% and none that have shrunk by more than 50% or who have developed one or more new tumors while on 131MIBG treatment will be taken off the study.
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.
NCT00125567 ↗ Stalevo in Early Wearing-Off Patients Completed Orion Corporation, Orion Pharma Phase 4 2005-08-01 The purpose of this study is to demonstrate in patients with Parkinson's disease that, when compared to levodopa/carbidopa, Stalevo will delay the time from initiation of study drug to the time an increase in antiparkinsonian medication is required due to inadequately controlled parkinsonian symptoms.
>Trial ID >Title >Status >Phase >Start Date >Summary

Clinical Trial Conditions for CARBIDOPA

Condition Name

Condition Name for CARBIDOPA
Intervention Trials
Parkinson's Disease 74
Parkinson Disease 44
Parkinson's Disease (PD) 9
Advanced Parkinson's Disease 9
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Condition MeSH

Condition MeSH for CARBIDOPA
Intervention Trials
Parkinson Disease 149
Dyskinesias 7
Depression 5
Cocaine-Related Disorders 5
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Clinical Trial Locations for CARBIDOPA

Trials by Country

Trials by Country for CARBIDOPA
Location Trials
United States 595
Italy 42
Germany 41
Canada 40
Spain 33
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Trials by US State

Trials by US State for CARBIDOPA
Location Trials
California 41
Florida 39
New York 32
Michigan 32
Texas 32
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Clinical Trial Progress for CARBIDOPA

Clinical Trial Phase

Clinical Trial Phase for CARBIDOPA
Clinical Trial Phase Trials
PHASE4 3
PHASE2 1
PHASE1 3
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Clinical Trial Status

Clinical Trial Status for CARBIDOPA
Clinical Trial Phase Trials
Completed 148
Recruiting 21
Not yet recruiting 13
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Clinical Trial Sponsors for CARBIDOPA

Sponsor Name

Sponsor Name for CARBIDOPA
Sponsor Trials
Bial - Portela C S.A. 15
Orion Corporation, Orion Pharma 14
Impax Laboratories, LLC 14
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Sponsor Type

Sponsor Type for CARBIDOPA
Sponsor Trials
Industry 178
Other 144
NIH 18
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CARBIDOPA Market Analysis and Financial Projection

Last updated: April 23, 2026

Clinical Trials Update, Market Analysis and Projections for Carbidopa

Carbidopa (dopamine decarboxylase inhibitor) is an established small-molecule therapy used in combination with levodopa for Parkinson’s disease and related parkinsonian syndromes. Commercially, market dynamics are dominated by fixed-dose levodopa/carbidopa regimens and by formulation-level competition (immediate-release versus extended-release, and intestinal gel where applicable). Patent and regulatory positioning are mature; near-term growth is driven by uptake of newer combination/formulation offerings, generic penetration cycles in many markets, and persistent demand in aging populations.

What clinical trials and label-relevant updates are active or recent for carbidopa?

Carbidopa development is concentrated in formulation optimization and combination strategies rather than new active moiety trials, given the long-established status of carbidopa itself. Trial activity generally appears in one of three buckets:

1) Levodopa/carbidopa formulation changes (bioavailability, dosing convenience, or delivery system)
2) Adjunct or comparative studies within standard-of-care levodopa regimens
3) Real-world and post-approval studies that support dosing, adherence, persistence, and adverse event profiling across populations

Because carbidopa’s role is typically fixed within levodopa combinations, trial reads and endpoints tend to map to:

  • OFF time reduction and dyskinesia control (for Parkinson’s disease cohorts)
  • Motor fluctuation metrics, UPDRS scores, and rescue medication use
  • Safety/tolerability (orthostatic hypotension, nausea, psychiatric effects secondary to dopaminergic regimens)

Market implication: clinical trial signals for “carbidopa” marketed products are usually signals for the specific levodopa/carbidopa formulation under evaluation, not for carbidopa as a standalone differentiator.

Actionable diligence focus: for any “carbidopa” trial watch, underwriting should bind the study to the exact product form (strength, release profile, delivery system) and geography, then map to expected payer reimbursement, formulary status, and generic substitution risk.

Which products anchor carbidopa demand in the market?

In practice, most commercial use of carbidopa flows through combination products with levodopa. Demand is therefore best analyzed by formulation competitive sets rather than by carbidopa API volume.

Key commercial anchors include:

  • Immediate-release levodopa/carbidopa tablets (multiple strengths; heavy generic presence in many markets)
  • Extended-release levodopa/carbidopa formulations (positioned to reduce dosing frequency and manage motor fluctuations)
  • Enteral levodopa/carbidopa gel systems (used in advanced Parkinson’s disease with refractory motor fluctuations; typically higher treatment cost and tighter access criteria)

Market structure takeaway: in many jurisdictions, generic tablets set a price floor, while extended-release and device-based/advanced delivery formulations capture premium pricing in defined patient subgroups.

Where does carbidopa fit across the competitive landscape (brand vs generic)?

Carbidopa is not typically assessed as a standalone “brand competitive asset” in the way newer CNS drugs are. Instead, brand value resides in:

  • Proprietary release technology and pharmacokinetic profiles for levodopa/carbidopa
  • Device-associated delivery systems for advanced disease
  • Fixed-dose combinations that reduce pill burden or caregiver workload

Generic substitution risk is high for immediate-release tablet classes where manufacturing entry is feasible and regulatory requirements are met. Premium opportunity concentrates in the differentiated release profiles and delivery methods where substitution is less straightforward.

How is the market projected to evolve (demand, mix, and pricing)?

Market growth for carbidopa-based regimens is anchored to:

  • Prevalence of Parkinson’s disease (rising due to demographic aging)
  • Long duration of therapy (chronic use with progressive dosing over time)
  • Formulation mix shift toward reduced dosing frequency and advanced delivery options

Projected growth is constrained by:

  • Generic penetration for immediate-release tablet categories
  • Payer pressure on premium-priced regimens
  • Therapy switching driven by disease-modifying candidates and competing symptomatic agents (primarily COMT inhibitors, MAO-B inhibitors, adenosine A2A antagonists, dopamine agonists, and device-based approaches)

Pricing dynamics by segment:

  • Immediate-release tablets: flat to declining in real terms due to generics and tendering
  • Extended-release: modest premium retention, but with generic/comparator pressure depending on local regulatory exclusivities
  • Advanced delivery systems: retain higher WAC and reimbursement rates in eligible patients, with demand determined by access pathways and clinician adoption

What is the market size today and what base-case projections matter?

Carbidopa is embedded in combination regimens, so market sizing requires mapping “levodopa/carbidopa” product categories. Without a defined dataset of scope (global versus region, tablets versus gel, or whether to include generics), a precise market-number forecast would be incomplete.

What can be stated with investment-grade clarity is the projection logic that determines the shape of future revenue:

  • Volume: grows with Parkinson’s prevalence and persistence
  • Real revenue: tracks mix shifts from immediate-release toward extended-release and advanced delivery
  • Downside: generic erosion for standard tablets and reimbursement tightening for advanced therapies
  • Upside: improved payer access, expanded eligibility criteria, and tighter differentiation of premium formulations

What patent and regulatory considerations drive timelines for carbidopa-containing products?

For carbidopa, the regulatory and IP profile is largely mature. Competitive timing is usually driven by:

  • Product-level IP (formulation, method, delivery device, or specific fixed-dose combinations)
  • Regulatory exclusivities for specific levodopa/carbidopa products (not carbidopa as a new active ingredient)
  • Generic approval pathways for immediate-release tablet equivalents

Actionable screening rule: treat “carbidopa” as a platform ingredient and underwrite IP risk at the product-form level. The market outcome depends on whether a differentiated formulation has enforceable protection beyond standard generics.

What is the near-term commercial outlook by geography?

At a functional level, geography shapes three variables:

  • generic intensity and procurement/tender behavior
  • reimbursement policies for advanced delivery systems
  • uptake of extended-release regimens

The expected pattern in most developed markets:

  • stable or modest growth in treated population
  • mix shift toward formats that reduce dosing burden
  • ongoing erosion of older immediate-release pricing

In emerging markets:

  • growth is more sensitive to diagnosis rates and access
  • generic availability often accelerates the price normalization process

Which clinical endpoints and evidence patterns influence uptake of premium levodopa/carbidopa regimens?

Payers and clinicians tend to key off:

  • OFF time and dyskinesia metrics
  • durability over repeated dosing days
  • adverse event profiles tied to dopaminergic therapy and comorbidities
  • patient subgroups with high baseline motor fluctuations

For business planning, evidence that supports:

  • reduced caregiver burden (fewer dosing events)
  • improved day-to-day motor function
  • lower rescue medication use typically correlates with formulary acceptance and adoption.

What do investors and R&D teams watch in future carbidopa-focused programs?

Because carbidopa is entrenched, the watchlist is formulation- and program-specific:

  • trial continuation patterns for extended-release schedules and advanced delivery options
  • head-to-head comparator designs vs best available symptomatic therapy
  • real-world evidence readouts that support persistence and adherence
  • manufacturing scale and supply reliability (important for chronic-use therapies)

Commercial KPI mapping:

  • time-on-therapy persistence
  • dose stability and titration success rates
  • discontinuation due to AEs
  • formulary win rate and net price trend

Key Takeaways

  • Carbidopa demand is driven by levodopa/carbidopa combination regimens, with competition anchored in formulation and delivery systems, not carbidopa novelty.
  • Clinical activity tied to carbidopa is usually optimization or comparative work that maps to motor fluctuation control and tolerability endpoints in Parkinson’s disease.
  • Market growth is driven by aging and persistent therapy, while immediate-release pricing is pressured by generics.
  • Revenue outlook depends on mix shift toward extended-release and advanced delivery systems and on product-level IP and reimbursement access.
  • Underwrite forecasts at the specific product-formulation level, because generic substitution risk varies strongly by dosage form and delivery approach.

FAQs

Is carbidopa growing faster because of new clinical evidence?

Carbidopa’s clinical impact is generally reflected through levodopa/carbidopa formulation outcomes (motor fluctuations, dosing convenience, tolerability), not through new carbidopa mechanism breakthroughs.

Which category is most exposed to generic competition?

Immediate-release levodopa/carbidopa tablets are typically most exposed due to substitution and procurement behavior.

What premium segments can sustain pricing?

Extended-release and advanced delivery systems can sustain pricing when they have demonstrable clinical differentiation and payer access.

How should market forecasts be built for carbidopa-containing therapies?

Use a two-layer model: (1) patient prevalence and persistence, then (2) mix and net price by formulation class.

What clinical endpoints drive adoption with payers?

OFF time reduction, dyskinesia control, rescue medication use, and tolerability outcomes linked to real-world dosing patterns.


References

[1] FDA. (n.d.). Drugs@FDA: FDA Approved Drug Products. https://www.accessdata.fda.gov/scripts/cder/daf/
[2] EMA. (n.d.). European public assessment reports (EPAR). https://www.ema.europa.eu/en/medicines
[3] ClinicalTrials.gov. (n.d.). Search results for carbidopa. https://clinicaltrials.gov/

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