Radiolabeling and in vivo evaluation of [ 11 C]AGH-44: a potential lead structure to develop a positron emission tomography radioligand for the 5-HT 7 receptor

AGH-44 is described as a selective low-basicity serotonin 7 receptor (5-HT 7 R) agonist. In this paper, we evaluate if AGH-44 can act as a lead structure to develop a 5-HT 7 R selective positron emission tomography (PET) tracer. 11 C-labeling of AGH-44 succeeded in a two-step, one-pot procedure in good yields. Subsequent PET studies showed that [ 11 C]AGH-44 displays low blood–brain-barrier passage in Long–Evans rats. Moreover, [ 11 C]AGH-44 brain accumulation showed to be independent on permeability glycoprotein (P-gp) efflux inhibition. Results from biodistribution and metabolism studies could neither explain the observed low brain uptake. As such, we believe that this scaffold is not an optimal starting point to develop a 5-HT 7 R selective PET tracer.