PAMPA
Encyclopedia
PAMPA is a method which determines the permeability of substances from a donor compartment, through a lipid
-infused artificial membrane into an acceptor compartment. A multi-well microtitre plate is used for the donor and a membrane/acceptor compartment is placed on top; the whole assembly is commonly referred to as a “sandwich”. At the beginning of the test, the drug is added to the donor compartment, and the acceptor compartment is drug-free. After an incubation period which may include stirring, the sandwich is separated and the amount of drug is measured in each compartment. Mass balance allows calculation of drug that remains in the membrane. To date, PAMPA models have been developed that exhibit a high degree of correlation with permeation across a variety of barriers, including Caco-2
cultures, the gastrointestinal tract
, blood-brain barrier
and skin.
The donor and/or acceptor compartments may contain solubilizing agents, or additives that bind the drugs as they permeate. To improve the in vitro
- in vivo
correlation and performance of the PAMPA method, the lipid, pH and chemical composition of the system is often designed with biomimetic considerations in mind.
The popularity of PAMPA in ADME
screening attests to its utility as an early stage, low-cost alternative to cellular models for research compounds. Although active transport
is not modeled by the artificial PAMPA membrane, up to 95% of known drugs are absorbed by passive transport
. Some experts support a lower figure, so the amount is open to some interpretation. Microtiter plates with 96 wells can be used for the assay which increases the speed and lowers the per sample cost.
Since the first publication by Kansy and coworkers, several companies developed their own versions of the assay. Early models incorporated iso-pH conditions in the compartments separated by a simple lipid membrane; subsequently, commercial products were introduced which incorporated more sophisticated lipid membranes. The commercial products helped ensure that medicinal chemists across different corporate labs within a worldwide organization used the same standardized methodology, reagents and obtained equivalent system performance as demonstrated with a set of test compounds. This has proved very useful as various operational activities have been outsourced to other countries.
As financial and other factors in pharmaceutical development continue to strain timelines and resources, PAMPA will most likely continue to play an ever-increasing role in laboratories wishing to increase their operating efficiencies and success rate.
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
-infused artificial membrane into an acceptor compartment. A multi-well microtitre plate is used for the donor and a membrane/acceptor compartment is placed on top; the whole assembly is commonly referred to as a “sandwich”. At the beginning of the test, the drug is added to the donor compartment, and the acceptor compartment is drug-free. After an incubation period which may include stirring, the sandwich is separated and the amount of drug is measured in each compartment. Mass balance allows calculation of drug that remains in the membrane. To date, PAMPA models have been developed that exhibit a high degree of correlation with permeation across a variety of barriers, including Caco-2
Caco-2
The Caco-2 cell line is a continuous line of heterogeneous human epithelial colorectal adenocarcinoma cells, developed by the Sloan-Kettering Institute for Cancer Research through research conducted by Dr...
cultures, the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
, blood-brain barrier
Blood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
and skin.
The donor and/or acceptor compartments may contain solubilizing agents, or additives that bind the drugs as they permeate. To improve the in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
- in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...
correlation and performance of the PAMPA method, the lipid, pH and chemical composition of the system is often designed with biomimetic considerations in mind.
The popularity of PAMPA in ADME
ADME
ADME is an acronym in pharmacokinetics and pharmacology for absorption, distribution, metabolism, and excretion, and describes the disposition of a pharmaceutical compound within an organism...
screening attests to its utility as an early stage, low-cost alternative to cellular models for research compounds. Although active transport
Active transport
Active transport is the movement of a substance against its concentration gradient . In all cells, this is usually concerned with accumulating high concentrations of molecules that the cell needs, such as ions, glucose, and amino acids. If the process uses chemical energy, such as from adenosine...
is not modeled by the artificial PAMPA membrane, up to 95% of known drugs are absorbed by passive transport
Passive transport
Passive transport means moving biochemicals and other atomic or molecular substances across membranes. Unlike active transport, this process does not involve chemical energy, because, unlike in an active transport, the transport across membrane is always coupled with the growth of entropy of the...
. Some experts support a lower figure, so the amount is open to some interpretation. Microtiter plates with 96 wells can be used for the assay which increases the speed and lowers the per sample cost.
Since the first publication by Kansy and coworkers, several companies developed their own versions of the assay. Early models incorporated iso-pH conditions in the compartments separated by a simple lipid membrane; subsequently, commercial products were introduced which incorporated more sophisticated lipid membranes. The commercial products helped ensure that medicinal chemists across different corporate labs within a worldwide organization used the same standardized methodology, reagents and obtained equivalent system performance as demonstrated with a set of test compounds. This has proved very useful as various operational activities have been outsourced to other countries.
As financial and other factors in pharmaceutical development continue to strain timelines and resources, PAMPA will most likely continue to play an ever-increasing role in laboratories wishing to increase their operating efficiencies and success rate.
See also
- Drug developmentDrug developmentDrug development is a blanket term used to define the process of bringing a new drug to the market once a lead compound has been identified through the process of drug discovery...
- Drug DiscoveryDrug discoveryIn the fields of medicine, biotechnology and pharmacology, drug discovery is the process by which drugs are discovered or designed.In the past most drugs have been discovered either by identifying the active ingredient from traditional remedies or by serendipitous discovery...
- Lipid bilayerLipid bilayerThe lipid bilayer is a thin membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around cells. The cell membrane of almost all living organisms and many viruses are made of a lipid bilayer, as are the membranes surrounding the cell nucleus...
- Caco-2Caco-2The Caco-2 cell line is a continuous line of heterogeneous human epithelial colorectal adenocarcinoma cells, developed by the Sloan-Kettering Institute for Cancer Research through research conducted by Dr...
cell-based permability
External links
- pION INC The first commercial supplier of complete PAMPA systems.
- BD Biosciences Pre-coated PAMPA Plate System.