title: The apparent permeabilities of Caco-2 cells to marketed drugs: magnitude, and independence from both biophysical properties and endogenite similarities.
abstract: We bring together fifteen, nonredundant, tabulated collections (amounting to 696 separate measurements) of the apparent permeability (P app) of Caco-2 cells to marketed drugs. While in some cases there are some significant interlaboratory disparities, most are quite minor. Most drugs are not especially permeable through Caco-2 cells, with the median P app value being some 16 ⋅ 10(-6) cm s(-1). This value is considerably lower than those (1,310 and 230 ⋅ 10(-6) cm s(-1)) recently used in some simulations that purported to show that P app values were too great to be transporter-mediated only. While these values are outliers, all values, and especially the comparatively low values normally observed, are entirely consistent with transporter-only mediated uptake, with no need to invoke phospholipid bilayer diffusion. The apparent permeability of Caco-2 cells to marketed drugs is poorly correlated with either simple biophysical properties, the extent of molecular similarity to endogenous metabolites (endogenites), or any specific substructural properties. In particular, the octanol:water partition coefficient, logP, shows negligible correlation with Caco-2 permeability. The data are best explained on the basis that most drugs enter (and exit) Caco-2 cells via a multiplicity of transporters of comparatively weak specificity.
authors.affiliation: School of Chemistry & The Manchester Institute of Biotechnology and Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), The University of Manchester , Manchester, Lancs , United Kingdom.
authors.forename: Steve
authors.initials: S
authors.lastname: O'Hagan
authors.affiliation: School of Chemistry & The Manchester Institute of Biotechnology and Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), The University of Manchester , Manchester, Lancs , United Kingdom.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Kell
keywords: Caco-2 cells; Cheminformatics; Facilitated diffusion/transport; Mathematical models; Oral absorption; Permeability; Transcellular transport; Transporter-mediated uptake; Transporters