We are soon going to release a report describing trends in the development and use of companion diagnostic biomarkers, and a key part of preparing this report was breaking down companion diagnostic biomarkers into relevant groups. A very clear initial division is between metabolic and non-metabolic biomarkers, as metabolic biomarkers are highly represented in companion diagnostics.
The most well-represented metabolic biomarkers are cytochrome p450 enzymes that metabolize drugs and for which there are relatively common mutations that affect how the drugs are metabolized (e.g. CYP2C19, CYP2D6). These and other such xenobiotic metabolic enzyme biomarkers are always used to guide dosing and safety.
Urea Cycle enzymes are also well-represented, and these are also used to guide dosing and safety for some drugs, but they are also used for patient selection, by identifying people with metabolic disorders for which certain drugs are indicated.
There are over twice as many drugs with metabolic biomarkers in the label than with non-metabolic, and the vast majority of these drugs use the metabolic biomarkers for dosing and safety. By contrast, non-metabolic biomarkers are more commonly used for patient selection.
For a more detailed breakdown of this topic, and a lot of other information about companion diagnostic biomarkers, these tests that use them, the drugs that they enable, and the companies that are developing those drugs, please look for our forthcoming report.