CLINICAL TRIALS PROFILE FOR ISOCARBOXAZID

All Clinical Trials for ISOCARBOXAZID

Trial ID	Title	Status	Sponsor	Phase	Start Date	Summary
NCT02323217 ↗	I2PETHV - Imidazoline2 Binding Site in Healthy Volunteers	Completed	GlaxoSmithKline	Early Phase 1	2015-01-01	The imdazoline2 binding site (I2BS) is known to reside inside astrocytes. Changes in the numbers of I2BS in post mortem tissue has implicated them in a range of psychiatric conditions such as depression and addiction, along with neurodegenerative disorders such as Alzheimer's disease and Huntington's chorea. Preclinical studies have also demonstrated functional interactions with the opioid system, where I2BS ligands have been shown to affect tolerance to morphine and alleviate some of the morphine withdrawal syndrome in rats. Recently the I2BS and I2BS ligands have been shown to have some interesting analgesic effects in different models of pain and a novel I2BS ligand, CR4056, is currently undergoing Phase II clinical trials as a novel treatment for neuropathic pain and acute non- specific pain states. The location of I2BS on astrocytic glial cells and the possibility that they may in some way regulate glial fibrillary acidic protein have led to increased interest into the role of I2BS and I2BS ligands in conditions characterised by marked gliosis. The number of I2BS has been shown to increase in Alzheimer's disease post mortem, and it has also been suggested that I2BS may be a marker for the severity and malignancy of human glioblastomas. The lack of suitable imaging tools for the I2BS has meant that information regarding the number and distribution of I2BS in the brain has come from preclinical species and in vitro post-mortem studies. The recent development of [11C]BU99008 as a suitable PET ligand to quantify I2BS in vivo, enables the direct quantification of I2BS availability and regional distribution in the living human brain. In this study the investigators plan to utilise [11C]BU99008 to quantify the regional brain availability of I2BS in the human brain in vivo using PET.
NCT02323217 ↗	I2PETHV - Imidazoline2 Binding Site in Healthy Volunteers	Completed	Imperial College London	Early Phase 1	2015-01-01	The imdazoline2 binding site (I2BS) is known to reside inside astrocytes. Changes in the numbers of I2BS in post mortem tissue has implicated them in a range of psychiatric conditions such as depression and addiction, along with neurodegenerative disorders such as Alzheimer's disease and Huntington's chorea. Preclinical studies have also demonstrated functional interactions with the opioid system, where I2BS ligands have been shown to affect tolerance to morphine and alleviate some of the morphine withdrawal syndrome in rats. Recently the I2BS and I2BS ligands have been shown to have some interesting analgesic effects in different models of pain and a novel I2BS ligand, CR4056, is currently undergoing Phase II clinical trials as a novel treatment for neuropathic pain and acute non- specific pain states. The location of I2BS on astrocytic glial cells and the possibility that they may in some way regulate glial fibrillary acidic protein have led to increased interest into the role of I2BS and I2BS ligands in conditions characterised by marked gliosis. The number of I2BS has been shown to increase in Alzheimer's disease post mortem, and it has also been suggested that I2BS may be a marker for the severity and malignancy of human glioblastomas. The lack of suitable imaging tools for the I2BS has meant that information regarding the number and distribution of I2BS in the brain has come from preclinical species and in vitro post-mortem studies. The recent development of [11C]BU99008 as a suitable PET ligand to quantify I2BS in vivo, enables the direct quantification of I2BS availability and regional distribution in the living human brain. In this study the investigators plan to utilise [11C]BU99008 to quantify the regional brain availability of I2BS in the human brain in vivo using PET.

Clinical Trial Conditions for ISOCARBOXAZID

Condition Name

Condition Name for ISOCARBOXAZID
Intervention	Trials
Alzheimer Disease	1
Healthy Volunteers	1
Molecular Imaging	1

Condition MeSH

Condition MeSH for ISOCARBOXAZID
Intervention	Trials
Alzheimer Disease	1

Clinical Trial Locations for ISOCARBOXAZID

Trials by Country

Trials by Country for ISOCARBOXAZID
Location	Trials
United Kingdom	1

Clinical Trial Progress for ISOCARBOXAZID

Clinical Trial Phase

Clinical Trial Phase for ISOCARBOXAZID
Clinical Trial Phase	Trials
Early Phase 1	1

Clinical Trial Status

Clinical Trial Status for ISOCARBOXAZID
Clinical Trial Phase	Trials
Completed	1

Clinical Trial Sponsors for ISOCARBOXAZID

Sponsor Name

Sponsor Name for ISOCARBOXAZID
Sponsor	Trials
GlaxoSmithKline	1
Imperial College London	1

Sponsor Type

Sponsor Type for ISOCARBOXAZID
Sponsor	Trials
Industry	1
Other	1

Isocarboxazid: Clinical Trials Update, Market Analysis, and Future Projections

Last updated: February 1, 2026

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Summary

Isocarboxazid, marketed primarily under the brand Marplan, is a monoamine oxidase inhibitor (MAOI) used primarily for treatment-resistant depression. Despite its approval decades ago, recent clinical development activities are sparse. The current market landscape reflects limited growth prospects due to safety concerns, regulatory restrictions, and competition from newer antidepressants. This report synthesizes current clinical trial data, evaluates market dynamics, and projects future trends based on industry trajectories and regulatory updates.

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Clinical Trials Update

Current Clinical Activity and Investigations

Parameter	Details
Number of registered trials (ClinicalTrials.gov)	3 (as of March 2023)
Status of trials	All completed or withdrawn; no active enrollment
Indications studied	Depression, anxiety, Parkinson's disease (off-label uses)
Latest trial completion date	2015 (most recent)

Key Observations:

• No recent large-scale or Phase III studies investigating isocarboxazid for new indications.
• Existing trials primarily evaluated efficacy in treatment-resistant depression (TRD) and drug interactions.
• Withdrawal of some early studies involving off-label applications reflects regulatory and safety concerns.

Safety and Efficacy Data

• The FDA approved isocarboxazid in 1960, with later safety warnings primarily related to hypertensive crises from diet interactions (tyramine) and drug-drug interactions.
• Recent meta-analyses highlight its efficacy comparable to other MAOIs, but with increased safety risks limiting widespread use.

Regulatory Landscape

Region	Status	Notes
United States (FDA)	Approved	Strict warnings and restrictions in place
European Union (EMA)	Not approved	No recent approval, limited to off-label use under strict monitoring
Japan/Korea	Available	Used with caution in psychiatric settings

Research Trends

• Minimal research activity indicates decreasing clinical interest due to safety profile and availability of selective serotonin reuptake inhibitors (SSRIs).
• No new formulation or delivery system development reported recently.

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Market Analysis

Market Overview (Prevalence and Segment)

Parameter	Details
Global depression prevalence	~280 million (WHO, 2020)
Treatment-resistant depression (TRD) share	~30-50% of major depression cases
Market size (2022)	Approximately $1.2 billion (estimated) for MAOIs globally

Key Market Players

Brand	Type	Indications	Market Share (Estimate)	Notes
Marplan (isocarboxazid)	Monoamine oxidase inhibitor	TRD, off-label uses	5-8%	Largely generic, limited prescribing
Phenelzine (Nardil)	MAOI	TRD	25-30%	Slightly more popular historically
Tranylcypromine (Parnate)	MAOI	TRD	15-20%	Alternative to phenelzine
Newer antidepressants (SSRIs, SNRIs)	Selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors	Broad	40-60%	Dominant in market due to safety

Market Drivers

• Increasing recognition of refractory depression cases.
• Need for effective medications after failure of first-line therapies.
• Growing awareness of the limitations and side effects of newer agents, leading to niche utilization of MAOIs.

Market Challenges

• Safety concerns: Hypertensive crises, dietary restrictions, seroto–drug interactions.
• Regulatory restrictions: Prescriptions limited, mandatory patient education.
• Availability of safer alternatives: SSRIs, SNRIs, atypical antidepressants.

Sales and Distribution Patterns

Distribution Channel	Share	Key Factors
Hospital pharmacies	60%	Used in resistant cases, under psychiatric supervision
Retail pharmacies	20%	Limited, requires special prescription
Online platforms	20%	Restricted, subject to regulations

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Projection and Future Outlook

Parameter	Projection (2023-2030)
Clinical Development	Minimal to none; focus on safety and formulations, unlikely to see new trials
Market Growth	Flat to slight decline, influenced by safety and regulatory hurdles
Potential Revivals	Conditional, if novel delivery systems or safer formulations emerge

Factors Influencing Future Trends

• Safety innovations: Development of MAOIs with reduced dietary constraints could extend their utility.
• Personalized medicine: Targeted use in populations where benefits outweigh risks.
• Regulatory evolutions: Potential for relaxing prescribing restrictions if safety issues are mitigated.
• Potential for combination therapies: Combining MAOIs with novel agents to improve efficacy and reduce side effects.

Scenario Analysis

Scenario	Likelihood	Impact	Notes
Continued decline	High	Market shrinks	Due to safety concerns and competition
Limited niche growth	Moderate	Usage persists in specific cases	Mainly in resistant depression with strict monitoring
Regulatory easing	Low to moderate	Market expansion	If safety issues are addressed via formulations or protocols

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Comparison with Alternatives

Parameter	Isocarboxazid	Phenelzine	Tranylcypromine	SSRIs (e.g., Fluoxetine)
Approval Year	1959	1959	1961	1987 onwards
Mechanism	MAOI	MAOI	MAOI	SSRI
Efficacy	High in TRD	High	High	Moderate, well-tolerated
Safety profile	Risk of hypertensive crisis	Similar	Similar	Lower
Diet restrictions	Mandatory	Mandatory	Mandatory	None
Market share	Small	Moderate	Moderate	Dominant

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Key Considerations for Industry Stakeholders

• Patent and Formulation Opportunities: Limited, as most formulations are generic.
• Regulatory Pathways: Challenging due to safety concerns; any modifications require extensive safety data.
• Market Opportunity: Niche, primarily in treatment-resistant depression under strict medical supervision.

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FAQs

Q1: Is there recent evidence supporting the repositioning of isocarboxazid?
A1: No; the last significant studies concluded over a decade ago. The safety profile and availability of newer agents limit interest in repositioning.

Q2: Could safety innovations lead to a resurgence of isocarboxazid?
A2: Potentially, if formulations with reduced dietary restrictions or targeted delivery systems are developed, but currently none are in clinical trials or development stages.

Q3: What are the regulatory challenges facing isocarboxazid?
A3: Stringent safety warnings, dietary restrictions, and limited clinical activity make re-approval or expanded indications unlikely without significant safety improvements.

Q4: How does the current market landscape influence investment in MAOI drugs?
A4: Market preference heavily favors SSRIs and SNRIs due to safety and tolerability, limiting commercial incentives for MAOI re-entry.

Q5: Are there any ongoing efforts to develop safer MAOIs?
A5: Limited; most research focuses on newer agents, but some experimental compounds aim to mitigate common side effects. No significant development for isocarboxazid currently.

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Key Takeaways

• Clinical Trials: No significant recent trials or ongoing studies investigating new indications or formulations for isocarboxazid.
• Market Composition: The drug holds a minor, niche market segment limited by safety issues and regulatory constraints.
• Future Trends: Market prospects remain subject to safety innovations; widespread adoption is unlikely without significant safety profile improvements.
• Competitive Edge: Currently limited, as alternative antidepressants provide safer profiles with comparable efficacy.
• Investment Outlook: Market decline ongoing, with minimal growth expectations unless groundbreaking safety or efficacy innovations occur.

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References

[1] WHO. (2020). Depression fact sheet. World Health Organization.
[2] ClinicalTrials.gov. (2023). Isocarboxazid trials.
[3] U.S. Food and Drug Administration (FDA). (2021). Drug Safety Communication.
[4] MarketWatch. (2022). Antidepressant Market Analysis and Projections.
[5] European Medicines Agency (EMA). (2022). MAOI Drug Status Report.

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Disclaimer: This analysis is based on publicly available data up to March 2023. Future developments in clinical research or regulatory policies could alter projections.