Solution-phase and solid-phase parallel synthesis and high throughput screening have enabled biologically active and selective compounds to be identified at an unprecedented rate. The challenge has been to convert these hits into viable development candidates. To accelerate the conversion of these hits into lead development candidates, early assessment of the physicochemical and pharmacological properties of these compounds is being made. In particular, in vitro absorption, distribution, metabolism, and elimination (ADME) assays are being conducted at earlier and earlier stages of discovery with the goal of reducing the attrition rate of these potential drug candidates as they progress through development. In this report, we present an eight-channel parallel liquid chromatography/mass spectrometry (LC/MS) system in combination with custom Visual Basic and Applescript automated data processing applications for high throughput early ADME. The parallel LC/MS system was configured with one set of gradient LC pumps and an eight-channel multiple probe autosampler. The flow was split equivalently into eight streams before the multiple probe autosampler and recombined after the eight columns and just prior to the mass spectrometer ion source. The system was tested for column-to-column variation and for reproducibility over a 17 h period (approximately 500 injections per column). The variations in retention time and peak area were determined to be less than 2 and 10%, respectively, in both tests. The parallel LC/MS system described permits time-course microsomal incubations (t o , t 5 , t 15 , t 30 ) to be measured in triplicate and enables estimations of t 1/2 microsomal stability. The parallel LC/MS system is capable of analyzing up to 240 samples per hour and permits the complete profiling up to two microtiter plates of compounds per day (i.e., 176 test substrate compounds ϩ sixteen controls). (J Am Soc Mass Spectrom 2002, 13, 155-165) © 2002 American Society for Mass Spectrometry A dvances in directed parallel synthesis and high throughput screening (HTS) have enabled large numbers of biochemically potent (active) and selective compounds to be identified at early stages of drug discovery [1][2][3]. However, the fact that a compound is active and selective does not necessarily make it an attractive drug development candidate. To convert these lead candidates into druggable molecules has proved elusive. It has been reported that a disproportionately large number of compounds entering development fail because of poor pharmacokinetics (nearly 40%) [3][4][5]. Consequently, it has been recognized that pharmacokinetic studies that assess absorption, distribution, metabolism, and elimination (ADME) should be initiated as early as possible in the discovery process in order to maximize the likelihood of development success and minimize development costs. More and more, discovery programs are taking advantage of high throughput in vitro assays and property-based design tools to assist medicinal chemists in making not only poten...

Evaluation and optimization of drug metabolism and pharmacokinetic data plays an important role in drug discovery and development and several reliable in vitro ADME models are available. Recently higher throughput in vitro ADME screening facilities have been established in order to be able to evaluate an appreciable fraction of synthesized compounds. The ADME screening process can be dissected in five distinct steps: (1) plate management of compounds in need of in vitro ADME data, (2) optimization of the MS/MS method for the compounds, (3) in vitro ADME experiments and sample clean up, (4) collection and reduction of the raw LC-MS/MS data and (5) archival of the processed ADME data. All steps will be described in detail and the value of the data on drug discovery projects will be discussed as well. Finally, in vitro ADME screening can generate large quantities of data obtained under identical conditions to allow building of reliable in silico models.

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