||||||||||GSK356278 / GSK Journal: Quantification of human brain PDE4 occupancy by GSK356278: A [(11)C](R)-rolipram PET study. (Pubmed Central) - Aug 15, 2019 We present the first report of a direct estimation of PDE4 blockade in the living human brain. In vivo affinity of GSK356278 for the PDE4, estimated in this early phase study, was combined with GSK356278 safety and tolerability data to decide on a therapeutic dose for future clinical development.