Screening in vitro

Rodgers KE, Leung N, Imamura T, et al. 1986. Rapid in vitro screening assay for immunotoxic effects of organophosphorus and carbamate insecticides on the generation of cytotoxic T lymphocyte responses. Pestic Biochem Physiol 26 292-301. 

Van de Waterbeemd, H. Which in vitro screens guide the prediction of oral absorption and volume of distribution Basic Clin. Pharmacol. Toxicol. 2005, 96, 152-165. 

The in vivo properties of compounds (464), (466) and (468)-(470) relative to (382) were investigated in two animal models a CBi agonist-induced hypotension rat model and a CBi agonist-induced hypothermia mouse model. Shown to be only moderately active in the in vitro screens, thiazole (464) and triazole (466) analogues failed to demonstrate convincing oral activity. Compound (468) was active in the hypotension model but showed... 

The lengthy permeability chapter (Chapter 7) recounts the study of many different artificial membrane formulations, comparing transport results of each to human jejunal permeabilities. A very promising in vitro screening system was described the double-sink sum-Pe PAMPA GIT model. It is most applicable to molecules that are classified as soluble in the BCS scheme. 

Sirover, MA, Loeb LA. 1976. Infidelity of DNA synthesis in vitro Screening for potential metal mutagens or carcinogens. Science 194 1434-1436. 

A massive body of evidence has already been presented clearly indicating that the medicinal plants of the Pacific Rim elaborate a broad array of cytotoxic substances. Most of these have been characterized using experimental procedures designed to examine the cytotoxicity of natural products against human tumor cell lines. These procedures involve in vitro screening where the viability of cultured cells after exposure to an extract or a purified substance is measured. 

Judson R, Houck K, Kavlock RJ, Knudsen T, Martin T, Mortensen HM, Reif D, Rotroff D, Shaha I, Richard AM, Dix DJ (2010) In vitro screening of environmental chemicals for targeted testing prioritization the ToxCast project. Environ Health Perspect 118 485-492... 

The effective permeability of ionizable molecules depends on pH, and the shapes of the permeability-pH profiles can be theoretically predicted when the pKa of the molecule is known [7]. The pH dependency of ionizable molecules is illustrated in Fig. 3.3 for a series of weak acids (A. Avdeef, not published). It is clear that if the wrong pH is used in screening the permeabilities of molecules, then highly promising molecules (e.g., probenecid Fig. 3.3) may be characterized as false negatives. The ideal pH to use for in vitro screening ought to reflect the in vivo pH conditions. 

There is also a need for cell systems that express a multiplicity of transporters. Cell line modification through cDNA-expression can be used to add missing functions to cells that are known to express only a subset of the enzymes or transporters that are needed and are known to be present in vivo. In this way, in vitro screening models can be improved. 

This model uses in vitro data to estimate the oral bioavailability ranges of chemically diverse compounds in a range of species, and represents a potentially powerful tool when combined with high-throughput in vitro screening. 

The next vague of tools will be around computational or in silico ADME approaches. These will allow to include ADME into the design of combinatorial libraries, the evaluation of virtual libraries, as well as in selecting the most promising compounds to go through a battery of in vitro screens, possibly even replacing some of these experimental screens. Several of these computational tools are currently under development as will be discussed in this volume. 

In vitro screening of the drug and its metabolites for effects on ion channels (especially lKr). 

Lindqvist, A., Hilke, S. and Skoglund, E. (2004) Generic three-column parallel LC-MS/MS system for high-throughput in vitro screens. Journal of Chromatography A, 1058 (1-2), 121-126. 

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