Overview

Companion diagnostics are assays or tests that are intended to assist physicians in making treatment decisions for their patients based on response to therapy. They do so by elucidating the efficacy and/or safety of a specific therapy for a targeted patient population.
There are two types companion diagnostics:
• Tests that have been developed after a drug has come to market. For examples the presence of acquired KRAS mutations in
tumor tissue as a measurement of response to targeted therapies such as Cetuximab.
• Tests that are being developed as a companion to the drug that is still in development.

Companion diagnostic co-development can potentially change the drug development process and commercialization of drug candidates significantly  by yielding safer drugs with better therapeutic efficacy in a faster, more cost-effective way.  To achieve this drug developers and diagnostic companies need to work closely together  Because biomarkers need to be qualified in the context of their intended use and test population, the development starts as part of the drug clinical trial process that will provide evidence of the marker’s clinical utility and the value of the test to accurately stratify patients based on their responder profile.

One specific field of impact is the development of companion diagnostics for targeted therapies in cancer. Many companies developing targeted therapies for cancer have also begun to consider the potential benefits of developing a diagnostic to pair with that treatment. To date, many of the pharmaceutical companies have started their in house efforts and established biomarker groups or even diagnostic groups. The trend is to establish drug-companion diagnostic co-Development rather than have both developments happen in isolation.