Preliminary biological evaluations of first brain‐penetrant GPR119‐based radiotracer in rodents and non‐human primates

Abstract

AbstractBackgroundG‐protein‐coupled receptors (GPCRs) plays a key role in regulating glucose metabolism. While GPR119 (an important GPCR) agonists have shown potential for improving neurologic and cognitive function in patients with AD and type2 diabetes mellitus (T2DM), clinical interventions targeting GPR119 will require accurate in vivo measures such as PET imaging. We recently synthesized a series of novel piperdine analogs, identifying two analogs (T1 and T2) with high GPR119 binding potency (2‐5 nM) for PET radiochemistry. Here we report their radiochemistry and initial biological evaluations in neuronal cells, normal rodents, and monkeys (vervets).Method[18F]T1/T2 radiochemistry was performed in TRASIS‐AIO automated module following [18F]¯‐based nucleophilic substitution of corresponding precursors. [18F]T1 and T2 in vitro assays were performed in three patient‐derived cell lines with different GPR119 expression (MDM‐MD‐231<NCI‐H1716<HepG2), with and without GPR119 agonists and non‐radioactive T1/T2. Dynamic 0‐60 min brain microPET/CT imaging and biodistribution were performed in normal balb/c mice (n=4). Healthy adult female vervets (n=6, 4.5‐6.7 kg) underwent 0‐90 min brain PET imaging. Standard uptake value (SUVmax) and time‐activity curves (TACs) were calculated for whole brain PET/MR images.ResultBoth [18F]T1 and T2 were produced in high radiochemical purities (>98%) and specific activities (∼3800‐4500 mCi/µmol), decay corrected to end of synthesis. Radioactive cell uptake was lower in MDM‐MD‐231 cells (lowest GPR119 expression) and higher in HepG2 cells (higher GPR119 expression); uptake also significantly increased with GPR119 agonists and T1/T2 treatments compared to baseline. [18F]T2 showed slightly better brain uptake in mice compared to [18F]T1 (SUVmax= 0.35±0.07 Vs. 0.55±0.09 g/mL). Biodistribution of [18F]T2 (%ID/mg = 1.01±0.09) also showed high brain uptake. SUVmax (avg=2.6±0.1 g/mL) and TACs of both [18F]T1 and [18F]T2 in monkey brains demonstrated rapid distribution across BBB within 10 min and favorable clearance within 90 min of tracer injection (Fig 1).ConclusionRadiochemistry was successfully automated and optimized. Cell uptake showed direct relationships between radiotracer uptake and GPR119 expression. MicroPET imaging, biodistribution in rodents and monkey PET imaging demonstrated excellent brain uptake and favorable pharmacokinetics, indicating BBB penetration. These data suggest for the first time that [18F]T1 and T2 have potential for imaging GPR119 in brains of humans with AD or T2DM.