Compound mixtures in Caco-2 cell permeability screens as a means to increase screening capacity

The purpose of this investigation was a study of simultaneous permeability measurement using compound mixtures (cassette dosing) as an alternative to single compound evaluation in order to increase the capacity of screens for intestinal drug permeability. Drug transport across Caco-2 monolayers was studied, both in the apical to basolateral and the basolateral to apical direction. The apparent permeability coefficients for ten compounds displaying different intestinal transport mechanisms were determined, first as single compounds and then as components of a mixture. Seven beta-adrenoceptor antagonists and baclofen were analysed simultaneously using reversed phase HPLC with UV detection, D-glucose and mannitol were measured by scintillation counting. The results indicated that the Papp from the mixture as donor phase correlated well with that of the single compounds and merely small changes in the Papp of each compound were observed between the single compound and mixture experiments. This minor variation resulted in a change in rank-order of the poorly permeable compounds in the mixture, however, without affecting their association with the permeability class according to the biopharmaceutics classification system (BCS). It can be concluded that the use of compound mixtures is a suitable method for improving the capacity in permeability screens. Further improvement of the throughput may be expected upon automatisation of permeability measurements using robotics combined with increased selectivity using LC-MS analysis.