PET imaging studies to investigate functional expression of mGluR2 using [¹¹C]mG2P001

Area of Science:

• Neuroscience
• Pharmacology
• Radiochemistry

Background:

• Metabotropic glutamate receptor 2 (mGluR2) is a key target for neurological and psychiatric disorders.
• Understanding mGluR2 function is crucial for developing targeted therapeutics.
• Positive allosteric modulators (PAMs) offer a promising therapeutic strategy for mGluR2.

Purpose of the Study:

• To investigate the positive allosteric modulation of mGluR2 using in vivo positron emission tomography (PET) imaging.
• To characterize a novel PET tracer, [11C]mG2P001, for visualizing mGluR2.
• To elucidate the binding mechanism and pharmacological effects of mGluR2 PAMs.

Main Methods:

• In vivo PET imaging in rats and non-human primates (NHPs) using the novel tracer [11C]mG2P001.
• In vitro binding studies using [3H]mG2P001 in CHO cells expressing mGluR2.
• Administration of unlabeled mG2P001 (mGluR2 PAM) and glutamate to assess tracer accumulation and binding cooperativity.

Main Results:

• Pretreatment with unlabeled mG2P001 significantly increased [11C]mG2P001 brain accumulation in rats, unlike orthosteric compounds.
• [11C]mG2P001 demonstrated suitability as an imaging ligand for mGluR2 in NHPs.
• In vitro studies confirmed the cooperative binding of mG2P001 with glutamate, enhancing tracer binding to mGluR2.
• Self-blocking studies in primates showed enhanced accumulation of [11C]mG2P001.

Conclusions:

• [11C]mG2P001 is a sensitive PET imaging biomarker for mGluR2 expression.
• The binding of [11C]mG2P001 is influenced by tissue glutamate concentration.
• This study validates [11C]mG2P001 for in vivo assessment of mGluR2 and its modulation, aiding drug discovery for neurological conditions.