First Evaluation of [C]R116301 as an In Vivo Tracer of NK1 Receptors in Man

Purpose: NK1 receptors have been implicated in various neuropsychiatric and other disorders. R116301 is a selective NK1 receptor antagonist. In this pilot study, [C]R116301 was evaluated as a potential positron emission tomography (PET) ligand for the NK1 receptor. Procedures: Two dynamic PET studies were performed in three normal volunteers before and after a blocking dose of aprepitant. Data were analyzed using striatum to cerebellum standardized uptake value (SUV) ratios. Results: Baseline SUV ratios at 60–90 min after injection ranged from 1.22 to 1.70. Following aprepitant administration, this specific signal was completely blocked. Aprepitant administration did not significantly affect uptake in cerebellum, confirming the absence of NK1 receptors in cerebellum. Conclusion: These preliminary results indicate that [C]R116301 has potential as a radioligand for in vivo assessment of NK1 receptors in the human brain.