Radiolabeled PBR Biomarker for High Brain Uptake Imaging
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Solution Overview
Problem
Current PET imaging agents, such as [11C]PK11195, have low brain uptake, high non-specific binding, and poor signal-to-noise ratio, limiting their sensitivity for detecting peripheral benzodiazepine receptor (PBR) levels and occupancy studies, particularly in central nervous system (CNS) applications.
Innovation Solution
The use of a radiolabeled form of 7-chloro-N,N,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4H-pyridazino[4,5-b]indole-1-acetamide as a biomarker for PBR levels, which exhibits high affinity and specificity, allowing for improved PET or SPECT imaging of PBR in both normal and pathological conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current PET imaging agents like [11C]PK11195 are used, then PBR imaging can be performed, but brain uptake is low and non-specific binding is high
Solution Approach 1:
The patent modifies the chemical structure of PK11195 by replacing the N-methylpiperidine ring with various substituted piperazine rings (e.g., 3-methoxypiperazine, 3-phenoxy piperazine, 4-methylpiperazine). These structural parameter changes result in compounds with higher brain uptake and improved signal-to-noise ratio while maintaining PBR binding affinity. The modifications optimize the balance between lipophilicity (for brain penetration) and specific binding characteristics.
2Ease of operation
If radiolabeled compounds are used for PBR imaging, then in vivo detection is enabled, but non-specific binding reduces imaging quality
Solution Approach 1:
The patent introduces specific substituents at defined positions on the piperazine ring (positions 3 and 4) to optimize local interaction characteristics with the PBR binding site. Examples include 3-methoxypiperazine, 3-phenoxy piperazine, and 4-methylpiperazine substitutions. These localized modifications enhance specific binding to PBR while reducing non-specific binding to other brain receptors, thereby improving imaging specificity without sacrificing in vivo detectability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the sensitivity and specificity of PBR imaging, providing a more effective tool for diagnosing and monitoring neurological and inflammatory conditions by offering higher brain uptake and reduced non-specific binding compared to existing agents.
Implementation Method 1
The reference PET PBR ligand, [11C]PK11195, has been used extensively in preclinical and clinical studies for in vivo imaging of PBR levels in a number of neuropathological conditions
Implementation Method 2
PBR is a member of the benzodiazepine receptor family and is located in the outer mitochondrial membrane of glial cells in the brain and in a number of peripheral tissues
Data Source
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AI summary
Use of a radiolabelled form of 7-chloro-?/,?/,5-trimethyl-4-oxo-3-phenyl-3,5-dihydro-4/-/- pyridazino[4,5-b]indole-1-acetamide as a biomarker for the detection, in an individual, of PBR levels associated with normal and pathological conditions. Method for the detection of PBR levels associated with normal and pathological conditions. Diagnostic kit.