ADMET stands for Absorption, Distribution, Metabolism, Excretion and Toxicity. The prediction of the ADMET properties plays an important role in the drug designing process because these properties account for the failure of about 60% of all drugs in the clinical phases.
The development of new drug candidates is really a very expensive process that consumes time and effort. Hence, there is an urgent need to develop new methods that are capable of predicting the important pharmacokinetic properties of drugs in a rapid and more accurate manner before being synthesized. Many computational models have emerged for the purpose of predicting ADMET parameters of drugs and drug-like compounds.
Current pharmaceutical research and development (R&D) is a high-risk investment which is usually faced with some unexpected even disastrous failures in different stages of drug discovery. One main reason for R&D failures is the efficacy and safety deficiencies which are related largely to absorption, distribution, metabolism and excretion (ADME) properties and various toxicities (T). Therefore, rapid ADMET evaluation is urgently needed to minimize failures in the drug discovery process. A web-based platform called ADMETlab for systematic ADMET evaluation of chemicals has been developed, based on a comprehensively collected ADMET database consisting of 288,967 entries.
Four function modules in the platform enable users to easily perform six types of drug-likeness analysis (five rules and one prediction model), 31 ADMET endpoints prediction (basic property: 3, absorption: 6, distribution: 3, metabolism: 10, elimination: 2, toxicity: 7), systematic evaluation and database/similarity searching.
The ADMET properties of our molecules are of vital importance. The ability to quickly and accurately predict these properties simply from the 2D structure of the molecule is extremely helpful in making decisions that can determine the success of your project. ADMET Predictor is state of the art ADMET property prediction software.
Absorption
For a compound to reach a tissue, it usually must be taken into the bloodstream, often via mucous surfaces like the digestive tract (intestinal absorption) before being taken up by the target cells. Factors such as poor compound solubility, gastric emptying time, intestinal transit time, chemical instability in the stomach, and inability to permeate the intestinal wall can all reduce the extent to which a drug is absorbed after oral administration.
Distribution
The compound needs to be carried to its effector site, most often via the bloodstream. From there, the compound may distribute into muscle and organs, usually to differing extents. After entry into the systemic circulation, either by intravascular injection or by absorption from any of the various extracellular sites, the drug is subjected to certain distribution processes that tend to lower its plasma concentration.
Metabolism
Compounds begin to break down as soon as they enter the body. The majority of small-molecule drug metabolism is carried out in the liver by redox enzymes, termed cytochrome P450 enzymes. As metabolism occurs, the initial (parent) compound is converted to new compounds called metabolites. Metabolites may also be pharmacologically active, sometimes more so than the parent drug.
Excretion
Compounds and their metabolites need to be removed from the body via excretion, usually through the kidneys (urine) or in the feces. Unless excretion is complete, accumulation of foreign substances can adversely affect normal metabolism.
There are three main sites where drug excretion occurs. The kidney is the most important site and it is where products are excreted through urine. Biliary excretion or fecal excretion is the process that initiates in the liver and passes through to the gut until the products are finally excreted along with waste products or feces. The last main method of excretion is through the lungs.
Toxicity
Sometimes, the potential or real toxicity of the compound is taken into account (ADME-Tox or ADMET). Parameters used to characterize toxicity include the median lethal dose (LD50) and therapeutic index.
