PET Whole Body Imaging Using a Peripheral Benzodiazepine Receptor Ligand [C-11]PBR28
|First Received Date ICMJE||December 2, 2006|
|Last Updated Date||May 1, 2013|
|Start Date ICMJE||November 2006|
|Primary Completion Date||Not Provided|
|Current Primary Outcome Measures ICMJE
||Biodistribution of [C-11]PBR28|
|Original Primary Outcome Measures ICMJE||Same as current|
|Change History||Complete list of historical versions of study NCT00407693 on ClinicalTrials.gov Archive Site|
|Current Secondary Outcome Measures ICMJE||Not Provided|
|Original Secondary Outcome Measures ICMJE||Not Provided|
|Current Other Outcome Measures ICMJE||Not Provided|
|Original Other Outcome Measures ICMJE||Not Provided|
|Brief Title ICMJE||PET Whole Body Imaging Using a Peripheral Benzodiazepine Receptor Ligand [C-11]PBR28|
|Official Title ICMJE||PET Whole Body Imaging Using a Peripheral Benzodiazepine Receptor Ligand [C-11]PBR28|
In this study we will examine where the radioactive tracer [11C]PBR28 is distributed in the body of healthy volunteers to calculate the radiation exposure to organs of the body. We will also test if [11C]PBR28 binds to your blood cells and compare with the binding in PET images.
The peripheral benzodiazepine receptor (PBR) is distinct from central benzodiazepine receptors associated with GABA(A) receptors. Although PBR was initially identified in peripheral organs such as kidneys, endocrine glands and lungs, later studies identified PBR in the central nervous system. In normal conditions, PBR is expressed in low levels in some neurons and glial cells. PBR can be a clinically useful marker to detect neuroinflammation because activated microglial cells in inflammatory areas express much greater levels of PBR than in microglial cells in resting conditions.
PBR has been imaged with positron emission tomography (PET) using [(11)C]1-(2-chlorophenyl-N-methylpropyl)-3-isoquinoline carboxamide (PK11195). However, this classical ligand provides only low levels of specific signals and is not sensitive to detect changes that occurred in vivo. Recently we developed a new ligand, N-acetyl-N-(2-[(11)C]methoxybenzyl)-2-phenoxy-5-pyridinamine [(11)C]PBR28), which showed much greater specific signals than [(11)C]PK11195 in non-human primates. Therefore, [(11)C]PBR28 is a promising PET ligand. However, radiation absorbed doses have not been estimated from human whole body imaging.
The initial purpose of this protocol is to estimate radiation absorbed doses of [11C]PBR28 by performing whole body imaging studies on ten healthy human subjects. The radiation absorbed doses are required to apply this PET ligand in various neurological and psychiatric disorders in the future.
Under the current and other protocols using [(11)C]PBR28, we found that some healthy subjects and patients have very low to no binding of [(11)C]PBR28. We studied approximately 188 subjects in total under protocols using [11C]PBR28 and found that 8.5% (16/188) had almost no binding of [(11)C]PBR28. Several published ligands have been tested and all of the tested ligands recently developed show low affinity to a subset of humans. By using [(11)C]PBR28, we need to exclude PBR28 nonbinders from the data to study changes in PBR. By using a PET ligand that binds equally to PBR28 binders and nonbinders, we would be able to study all subjects. We also confirmed that PBR28 nonbinders determined by PET do not show binding in in vitro binding assays using blood cells.
We wish to test new ligands currently being developed in our chemistry group by obtaining blood samples from additional PBR28 nonbinders (= low affinity binders) and by performing in vitro binding assays. Because our preliminary analysis of whole body imaging has shown that the differences between PBR28 binders and nonbinders might somewhat vary among organs and the cause of the nonbinding phenomenon is not fully understood, after identifying PBR28 nonbinders by binding assays, we will perform whole body imaging using [(11)C]PBR28.
|Study Type ICMJE||Interventional|
|Study Phase||Phase 1|
|Study Design ICMJE||Allocation: Non-Randomized
Endpoint Classification: Pharmacokinetics Study
Intervention Model: Single Group Assignment
Masking: Open Label
Primary Purpose: Diagnostic
|Intervention ICMJE||Drug: [C-11]PRB28
|Study Arm (s)||Not Provided|
* Includes publications given by the data provider as well as publications identified by ClinicalTrials.gov Identifier (NCT Number) in Medline.
|Recruitment Status ICMJE||Recruiting|
|Estimated Enrollment ICMJE||100|
|Estimated Completion Date||March 2015|
|Primary Completion Date||Not Provided|
|Eligibility Criteria ICMJE||
All subjects must be healthy and aged 18-65 years.
|Ages||18 Years to 65 Years|
|Accepts Healthy Volunteers||Yes|
|Location Countries ICMJE||United States|
|NCT Number ICMJE||NCT00407693|
|Other Study ID Numbers ICMJE||070035, 07-M-0035|
|Has Data Monitoring Committee||Not Provided|
|Responsible Party||Not Provided|
|Study Sponsor ICMJE||National Institute of Mental Health (NIMH)|
|Collaborators ICMJE||Not Provided|
|Information Provided By||National Institutes of Health Clinical Center (CC)|
|Verification Date||January 2013|
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