Companion diagnostic test associated with a targeted therapy: definitions and assessment method

Stratified medicine is a therapeutic approach based on drug/diagnostic test associations. The objective of the diagnostic test is to use a marker predictive for the effect of the treatment in order to select the patients to whom it is administered so as to treat only the subpopulation that will benefit from it. In this context, demonstrating the efficacy of the treatment in a limited subpopulation identified by its status for the marker logically leads to the prescription of the treatment being restricted to this subpopulation in its marketing authorisation, making this test a regulatory requirement.

In this guide, HAS defines the precise semantics of the concepts of targeted therapy and companion diagnostic test which thus have to meet strict requirements in terms of evidence. The fundamental principle for the assessment by HAS of a diagnostic test associated with a stratified therapy lies in the fact that recognition of the designations "companion” test and "targeted” therapy depends on whether or not the clinical utility of the diagnostic test is demonstrated. Demonstrating the clinical utility of the test is necessary because it shows the test’s ability to improve patient clinical outcomes and provide added value in terms of optimising patient management. As a consequence, it proves the added value provided by the test compared with a diagnostic test in that it allows a subpopulation to be selected only if a marker is identified.

Since the treatment/test association is an inseparable unit, the assessment of the diagnostic test must be included in that of the treatment. This has direct consequences for study methodologies that may or may not have the ability to provide the evidence needed to meet the level of requirements conferring the added value of a “companion” to a “standard” diagnostic test. In this guide, HAS therefore aimed to present the principles it will use to assess diagnostic tests associated with treatments, with two objectives: firstly to ensure the transparency of its assessments, and secondly to provide the healthcare industry with the specifications needed to conduct clinical studies that are of a quality consistent with the expected requirements.

This guide presents a practical summary of the methodological principles that will guide HAS assessments, the concepts implemented being described in a methodological annex entitled “Companion diagnostic test associated with a targeted therapy: Scientific annex”.