Permeability of lipophilic compounds in drug discovery using in-vitro human absorption model, Caco-2

• Published in: International journal of pharmaceutics Vol. 222; no. 1; pp. 77 - 89
• Main Authors: Krishna, Gopal, Chen, Kwang-jong, Lin, Chin-chung, Nomeir, Amin A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 03.07.2001; Elsevier
• Subjects: Biological and medical sciences; Bovine serum albumin; Caco-2; Caco-2 Cells - metabolism; Chemistry, Pharmaceutical; General pharmacology; Humans; Lipophilic compounds; Mannitol - pharmacokinetics; Medical sciences; Molecular Weight; Non-specific binding; Oral absorption; Permeability; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Progesterone - pharmacokinetics; Propranolol - pharmacokinetics; Structure-Activity Relationship; Bovine serum albumin; HTS, high-throughput screening; PEG, polyethylene glycol; TEER, trans-epithelial electrical resistance; AP, apical or donor side; Non-specific binding; BA, basolateral or receiver side; Permeability; Papp, apparent permeability; p-gp, P-glycoprotein; TM, transport media; Oral absorption; Lipophilic compounds; mol. wt., molecular weight; dpm, disintegration per minute; Caco-2; NME's, new molecular entities; SD, sample standard deviations; Human; Pharmaceutical technology; Digestive system; Biological transport; Albumin; Partition coefficient; In vitro; Modeling; Protein; Lipophilic compound; Dimethyl sulfoxide; Established cell line; Mannitol; Mathematical model; Propranolol; Physicochemical properties
• ISSN: 0378-5173; 1873-3476
• DOI: 10.1016/S0378-5173(01)00698-6

Highly lipophilic compounds are often encountered in the early stages of drug discovery. The apparent permeability (Papp) of these compounds in Caco-2 cell could be underestimated because of considerable retention by the Caco-2 monolayer and non-specific binding to transwell surface. We have utilized a general approach for the determination of permeability of these compounds, which includes the addition of 1–5% DMSO in the apical (AP) and 4% bovine serum albumin (BSA) in the basolateral (BA) side. Two highly lipophilic and highly protein bound Schering compounds, SCH-A and SCH-B, exhibited poor recovery and low Papp in the conventional Caco-2 system that included 1% DMSO in the AP and BA sides. In contrast, both compounds were well absorbed in cynomolgus monkeys. Inclusion of BSA (up to 4%) in the BA side provided necessary absorptive driving force similar to in vivo sink conditions improving both recovery and Papp of these compounds as well as progesterone, a model highly lipophilic and highly protein bound compound. Whereas, the recovery and Papp of mannitol (high recovery, low permeability) and propranolol (high recovery, high permeability) remained unaffected. The presence of 4% BSA increased Papp of SCH-A, SCH-B, and progesterone by five-, four-, and three-fold, respectively. We also compared this approach with a second, based on the disappearance of the compound from the AP side, which resulted in a reasonable estimate of the permeability (23.3×10 −6 cm/s) for SCH-A. The results demonstrated that the reliable estimates of permeability of highly lipophilic compounds that are subjected to considerable retention by the cell monolayer and exhibit non-specific binding are obtained by the addition of BSA to the BA side.