Pharmacogenomics can be defined as the study of how a person’s genetic makeup determines response to a drug. Although any number of labs and techniques can detect mutant genes, this area of pharmacogenomics was ripe for proprietary tests, invented alongside the drug and owned by the drug developer and/or a partner in the diagnostics field.

This business opportunity evolved as more drugs were approved with companion diagnostics. Unfortunately, the introduction of these new drugs has not been accompanied by specific predictive tests allowing for a rational and economical use of the drugs.

Companion diagnostics and their companion therapies are what's being pushed as "personalized medicine" as they enable the identification of likely responders to therapies that work in patients with a specific molecular profile. However, companion diagnostics tend to only answer a targeted drug-specific question and may not address other important clinical decision needs.

These companion diagnostics are being used to predict responsiveness and determine candidacy for a particular therapy often included in drug labels as either required or recommended testing prior to therapy initiation. I certainly would not want to be "denied" treatment because of gene testing. Gene testing is not a clear predictor of a lack of benefit from particular targeted therapies.

Anyone familiar with cellular biology knows that having the genetic sequence of a known gene (genotype) does not equate to having the disease state (phenotype) represented by that gene. It requires specific cellular triggers and specialized cellular mechanisms to literally translate the code into the work horse of the cellular world - proteins.