Table of Contents

• Overview of the Radiotracer
• Clinical Trial Design and Objectives
• Target Population and Enrollment
• Administration and Dosing
• Primary Outcomes and Measurements
• Clinical Significance for Parkinson’s Disease

Overview of the Radiotracer

(1-(111C)METHYLPIPERIDIN-4-YL)METHYL 5-AMINO-6-CHLORO-1,4-BENZODIOXINE-8-CARBOXYLATE is a radioactive compound used in medical imaging research, particularly in studies examining brain function and receptor distribution^[1]. This substance is also known by its shorter scientific names, [11C]SB207145 and [C11]-SB207145, which refer to the same molecular compound^[1].

The compound functions as a radiotracer, meaning it contains a small amount of radioactive material that allows specialized imaging equipment to track where it goes in the body^[1]. Specifically, this radiotracer is designed to bind to serotonergic 5-HT4 receptors in the brain, which are specialized proteins on the surface of brain cells that respond to serotonin, an important chemical messenger^[1].

In clinical research, (1-(111C)METHYLPIPERIDIN-4-YL)METHYL 5-AMINO-6-CHLORO-1,4-BENZODIOXINE-8-CARBOXYLATE helps scientists visualize and measure how many of these 5-HT4 receptors are present in different brain regions^[1]. This information is particularly valuable for understanding neurological conditions like Parkinson’s disease, where changes in brain chemistry and receptor distribution may contribute to symptoms^[1].

Clinical Trial Design and Objectives

The primary clinical trial investigating (1-(111C)METHYLPIPERIDIN-4-YL)METHYL 5-AMINO-6-CHLORO-1,4-BENZODIOXINE-8-CARBOXYLATE is an exploratory study focused on understanding the expression of serotonergic 5-HT4 receptors in patients with Parkinson’s disease^[1]. The trial is registered under the identification number 2022-503089-57-00 and has received authorization to proceed^[1].

This is a Phase 4 clinical trial, which means the radiotracer has already been approved for use and researchers are now exploring additional applications and gathering more detailed information about its use in specific patient populations^[1]. Phase 4 studies typically occur after a substance has demonstrated safety and effectiveness in earlier trial phases.

The main objective of this trial is to compare the expression of 5-HT4 receptors in patients with mild to moderate Parkinson’s disease to age-matched healthy control subjects^[1]. By making this comparison, researchers hope to identify specific differences in receptor distribution and density that may be associated with Parkinson’s disease.

The study design is interventional, meaning participants actively receive the radiotracer substance and undergo imaging procedures as part of the research protocol^[1]. This differs from observational studies where researchers simply monitor participants without administering specific treatments or interventions.

Target Population and Enrollment

The clinical trial investigating (1-(111C)METHYLPIPERIDIN-4-YL)METHYL 5-AMINO-6-CHLORO-1,4-BENZODIOXINE-8-CARBOXYLATE is designed to enroll a total of 35 participants^[1]. This enrollment includes two distinct groups that will be compared throughout the study.

The first group consists of patients with Parkinson’s disease who have mild to moderate symptoms^[1]. The focus on mild to moderate disease stages is important because:

• These patients are typically stable enough to safely participate in imaging studies
• The disease has progressed enough to show measurable changes in brain receptor expression
• Results may be most applicable to the majority of diagnosed Parkinson’s patients who are in these disease stages
• Early to moderate stages allow researchers to identify changes before extensive brain damage occurs

The second group consists of age-matched healthy control subjects^[1]. These are individuals who do not have Parkinson’s disease or other neurological conditions. Age-matching is crucial because:

• Brain receptor expression naturally changes with age
• Comparing patients to similarly aged healthy individuals ensures that observed differences are due to disease rather than normal aging
• It provides a baseline for what normal 5-HT4 receptor expression looks like in the relevant age group

Administration and Dosing

In the clinical trial, (1-(111C)METHYLPIPERIDIN-4-YL)METHYL 5-AMINO-6-CHLORO-1,4-BENZODIOXINE-8-CARBOXYLATE is administered through intravenous injection^[1]. This means the radiotracer is delivered directly into a vein, typically in the arm, allowing it to quickly enter the bloodstream and circulate throughout the body, including to the brain.

The dose used in this trial is 500 megabecquerels (MBq)^[1]. A megabecquerel is a unit that measures radioactivity, indicating how much radioactive material is present in the dose. This specific dose level has been selected to:

• Provide sufficient radioactive signal for clear imaging of brain receptors
• Maintain safety by keeping radiation exposure within acceptable limits for research participants
• Allow for accurate measurement of receptor binding across different brain regions

After intravenous administration, the radiotracer travels through the bloodstream and crosses into the brain, where it binds to 5-HT4 receptors^[1]. The radioactive component of the molecule allows specialized imaging equipment to detect where the tracer has accumulated, creating detailed pictures of receptor distribution throughout the brain.

Primary Outcomes and Measurements

The primary outcome being measured in this clinical trial is the difference in binding of the radiotracer [11C]SB207145 to the 5-HT4 receptor between Parkinsonian patients and control subjects^[1]. This measurement provides crucial information about how Parkinson’s disease affects the serotonergic system in the brain.

For each participant in the study, researchers calculate the specific binding of the tracer for each voxel with respect to a reference zone^[1]. A voxel is a three-dimensional unit of measurement in brain imaging, similar to a pixel in a two-dimensional image but with depth added. By analyzing binding at the voxel level, researchers can create highly detailed maps of receptor distribution throughout the entire brain.

The reference zone used in this study is the white matter of the cerebellum^[1]. This brain region is chosen as a reference because:

• It typically has very low density of 5-HT4 receptors
• It provides a baseline measurement of non-specific binding (tracer present in the area but not attached to target receptors)
• Comparing other brain regions to this reference allows researchers to calculate true specific binding to 5-HT4 receptors
• It is a standard approach in neuroimaging studies to improve measurement accuracy

The measurement process involves sophisticated imaging techniques that capture the distribution of radioactivity throughout the brain^[1]. By comparing the amount of tracer binding in various brain regions between Parkinson’s patients and healthy controls, researchers can identify specific areas where receptor expression differs due to the disease.

Clinical Significance for Parkinson’s Disease

Understanding the expression of serotonergic 5-HT4 receptors in Parkinson’s disease has important implications for both research and potential future treatments^[1]. While Parkinson’s disease is primarily known as a disorder affecting dopamine-producing brain cells, the serotonin system also plays a significant role in the disease and its symptoms.

The serotonergic system is involved in several functions that are often affected in Parkinson’s disease, including:

• Mood regulation: Many Parkinson’s patients experience depression and anxiety, which may be related to changes in serotonin receptor expression
• Cognitive function: Memory and thinking abilities can be affected in Parkinson’s disease, and serotonin receptors play a role in these processes
• Motor control: While dopamine is the primary neurotransmitter for movement, serotonin also contributes to motor function and may influence Parkinson’s symptoms
• Sleep patterns: Sleep disturbances are common in Parkinson’s disease and are influenced by the serotonergic system

By using (1-(111C)METHYLPIPERIDIN-4-YL)METHYL 5-AMINO-6-CHLORO-1,4-BENZODIOXINE-8-CARBOXYLATE to visualize 5-HT4 receptor expression, this trial aims to provide detailed information about how the serotonergic system changes in Parkinson’s disease^[1]. This information could potentially:

• Help identify biomarkers for disease progression
• Guide development of new treatments targeting the serotonergic system
• Improve understanding of why certain non-motor symptoms occur in Parkinson’s disease
• Assist in developing more personalized treatment approaches based on individual receptor expression patterns

The exploratory nature of this study means it is designed to generate new hypotheses and insights rather than test a specific treatment^[1]. The findings from this trial may lay the groundwork for future research into serotonin-based therapies for Parkinson’s disease or help explain why existing treatments work differently in different patients.