Metabolism Studies using Caco-2 Cells

The inherent enzymatic activity seems low also in other cell lines used for screening, such as MDCK and LLC-PK1 cells [158], Both MDCK and LLC-PK1 cells have been transfected with CYP3A4 and MDR1 for studying the concert action between dmg metabolism and secretion via efflux transporters [158]. 

This work was supported by grants from the Swedish Research Council, the Swedish Governmental Agency for Innovation Systems, and AstraZeneca. 

1 U rijH ll, A.-L. (1997) In vitro absorption studies and their relevance to absorption from the GI tract. Drug Development and Industrial Pharmacy, 23, 879-892. 

2 Ungell, A.-L. and Abrahamsson, B. (2001) Biopharmaceutical support in candidate drug selection, in Pharmaceutical Preformulation and Formulation. A Practical Guide from Candidate Drug Selection to Commercial Dosage Formulation (ed. M. Gibson), Interpharm Press. 

3 Lipinski, C.A. (2000) Drug-like properties and the causes of poor solubility and poor permeability. Journal of Pharmacological and Toxicological Methods, 44, 235-249. 

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In-vitro models can provide preliminary insights into some pharmacodynamic aspects. For example, cultured Caco 2 cell lines (derived from a human colorectal carcinoma) may be used to simulate intestinal absorption behaviour, while cultured hepatic cell lines are available for metabolic studies. However, a comprehensive understanding of the pharmacokinetic effects vfill require the use of in-vivo animal studies, where the drug levels in various tissues can be measured after different dosages and time intervals. Radioactively labelled drugs (carbon-14) may be used to facilitate detection. Animal model studies of human biopharmaceutical products may be compromised by immune responses that would not be expected when actually treating human subjects. 

In vitro assays are increasingly being used. Some of the reasons are cost, availability of more rapid results, and avoidance of negative publicity. Assays such as cytochrome P-450 enzymes, the Ames test, and the mouse lymphoma tk test are in vitro methods. For absorption studies, Caco-2 (Exhibit 5.9) and Madin-Darby canine kidney cell assays are now routinely used. Hepatocyte cell lines with metabolism capacity are being developed to test drug metabolism and toxicity. All these examples show that, where possible, pharmaceutical firms are gradually dispensing with animal studies. 

Caco-2 cells have also been used to study the metabolism of phenolic acids. Contrary to the transport studies, which usually use the cells grown on semipermeable filters (two compartments), the cultures used to study metabolism are prepared with cells grown and partially differentiated on dishes (one... 

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