Next, to gauge the suitability of SSAs for oral dosing, 9 was subjected to a Caco-2 permeability assay. This assay is used to both predict human intestinal permeability and investigate drug efflux, predicting in vivo compound absorption. This assay allows assessment of a compound's ability to undergo transport from the apical to the basolateral (A-B) compartments of the cell monolayer and vice versa (B-A). Similarly to previously tested SSAs, including 1, 39 9 was confirmed to poorly permeate the monolayer in the A-B direction (permeability coefficient -Papp (A-B) = 0.17 x 10 -6 cm/s), however high permeability in the B-A direction was observed (Papp (B-A) = 16.76 x 10 -6 cm/s) (Table † ). This data suggests that the compound is intrinsically permeable but is likely to be an efflux substrate, based on the poor permeability observed with drug transporters present. This is likely to result in poor absorption when dosed orally and therefore further development would be necessary for these agents to become suitable for oral administration.