In vitro assays are a type of scientific test performed in a laboratory. There are two components that must be present in order for a test to qualify as an in vitro assay. First, the test must be performed in vitro, which means in a test tube or other sterile container, rather than in a living organism. Second, the test must be an assay, which means that it is a measure of the activity of a drug on a sample of organic tissue. These tests are useful when developing new drugs because those that are ineffective can be quickly ruled out, allowing scientists to focus their attention on the ones that may prove successful.
The process of bringing a new drug to market is complicated and time consuming. Using in vitro assays significantly cuts down on the time it takes to rule out an ineffective drug. Tissue samples, such as sections of organ or blood, can be infected with a disease and potential treatments can be administered to the samples. Viewing the interaction between the drug and the sample in a test tube allows scientists to quickly determine whether the drug has the desired effect. Drugs that show promise can then move on to other phases of testing, while those that do not seem to work can be abandoned.
Aside from speeding up the process of testing new drugs, in vitro assays also decrease the costs of drug development. Using tissue samples allows many tests to be performed at once. In an vitro assay, it is possible to use samples that can be replenished, such as samples of blood. Though many of these samples are collected from animals, the cost in animal life for in vitro testing is much lower than that for in vivo tests.
In vitro assays may use human tissue samples. It is often medically unethical to do testing on live humans, but tests can be performed on samples of human blood or on other tissue samples collected from cadavers. The use of human tissue samples allows scientists to acquire a better understanding of how a certain drug will affect human cells. Though testing still requires an in vivo phase, results that prove to be promising during the in vitro portion of the tests can indicate whether a new drug will be effective on human patients.