18F CB2 Radioligand for Selective PET Imaging
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Solution Overview
Problem
Current PET tracers for Cannabinoid Receptor 2 (CB2) lack selectivity and specificity, leading to unfavorable signal-to-noise ratios due to high lipophilicity and the use of short-lived isotopes like 11C, and there is a need for a tracer with high selectivity and specificity for CB2 containing the longer-lived 18F isotope to facilitate distribution and use.
Innovation Solution
A radiolabeled compound of formula (I) is developed, which selectively binds to CB2 receptors, incorporating a fluorine atom for improved physicochemical and biological properties, allowing for high specificity and reduced non-specific binding, suitable for PET imaging and tissue autoradiography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current PET tracers for CB2 are used, then CB2 receptor binding is achieved, but selectivity and specificity are low due to high lipophilicity and use of short-lived isotopes
Solution Approach 1:
The patent changes the radioactive isotope parameter from short-lived 11C to longer-lived 18F, and modifies the chemical structure by incorporating a fluorine atom at position 3 of the pyridine ring. These parameter changes improve the tracer's selectivity and specificity for CB2 receptors while enhancing the signal-to-noise ratio through reduced non-specific binding.
2Adaptability or versatility
If short-lived isotopes like 11C are used, then rapid decay reduces radiation exposure, but distribution and use are limited due to short half-life
Solution Approach 1:
The patent changes the isotope parameter from 11C (half-life ~20 minutes) to 18F (half-life ~110 minutes). This parameter change extends the duration of action, enabling broader distribution and more flexible use of the PET tracer throughout the imaging process and patient monitoring.
3Speed
If high lipophilicity is present in CB2 tracers, then membrane permeability is improved, but non-specific binding increases reducing selectivity
Solution Approach 1:
The patent introduces a fluorine atom at the specific local position (position 3) of the pyridine ring structure. This local modification improves membrane permeability while the fluorine's specific electronic and steric properties reduce non-specific binding, thereby maintaining selectivity for CB2 receptors.
Solution Approach 2:
The patent changes the chemical parameter by substituting a hydrogen atom with a fluorine atom at position 3 of the pyridine ring. This parameter change optimizes the balance between lipophilicity (for membrane permeability) and specificity (for reducing non-specific binding).
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
The compound of formula (I) demonstrates high selectivity and specificity for CB2 receptors, enabling effective PET imaging and diagnostic applications, including assessing receptor expression and occupancy, and predicting patient response to CB2 ligand treatments.
Implementation Method 1
The compound of formula (I) selectively binds to CB2 receptors, enabling effective PET imaging and diagnostic applications
Implementation Method 2
incorporating a fluorine atom for improved physicochemical and biological properties, allowing for high specificity and reduced non-specific binding, suitable for PET imaging and tissue autoradiography
Data Source
Figure 1
AI summary
The present invention relates to a compound of formula (I) wherein R1, R2, and R3 are defined as in the description and in the claims. The compound of formula (I) can be used as a radiolabeled ligand.