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  1. In Vitro Diagnostics

Companion Diagnostics

A companion diagnostic is a medical device, often an in vitro diagnostic (IVD), which provides information that is essential for the safe and effective use of a corresponding drug or biological product. 

Companion diagnostics can:

  • identify patients who are most likely to benefit from a particular therapeutic product,
  • identify patients likely to be at increased risk for serious side effects as a result of treatment with a particular therapeutic product; or
  • monitor response to treatment with a particular therapeutic product for the purpose of adjusting treatment to achieve improved safety or effectiveness.

If the diagnostic test is inaccurate, then the treatment decision based on that test may not be optimal.

Related FDA Guidance Documents

On August 6, 2014, the FDA issued the final guidance, In Vitro Companion Diagnostic Devices, to help companies identify the need for companion diagnostics at an earlier stage in the drug development process and to plan for co-development of the drug and companion diagnostic test. The ultimate goal of the guidance is to stimulate early collaborations that will result in faster access to promising new treatments for patients living with serious and life-threatening diseases.

On July 15, 2016, the FDA released the draft guidance, Principles for Codevelopment of an In Vitro Companion Diagnostic Device with a Therapeutic Product. This guidance document, when finalized, is intended to be a practical guide to assist therapeutic product sponsors and IVD sponsors in developing a therapeutic product and an accompanying IVD companion diagnostic.

On April 13, 2020, the FDA published the final guidance, “Developing and Labeling In Vitro Companion Diagnostic Devices for a Specific Group or Class of Oncology Therapeutic Products," which is intended to facilitate class labeling on diagnostic tests for oncology therapeutic products, where scientifically appropriate. This final guidance discusses considerations for the development and labeling of companion diagnostics to support a broader labeling claim such as use with a specific group of oncology therapeutic products, rather than listing an individual therapeutic product(s).

In a related action, on June 21, 2023, the FDA issued a final guidance, “Oncology Drug Products Used with Certain In Vitro Diagnostic Tests: Pilot Program,” to announce and describe the FDA’s voluntary pilot program for certain CDER-regulated oncology drug products1 used with certain in vitro diagnostic tests. FDA intends to pilot a new approach to provide greater transparency regarding performance characteristics that certain tests for oncology biomarkers used to select certain oncology drug treatments should meet. For additional information on this pilot program, visit Oncology Drug Products Used with Certain In Vitro Diagnostics Pilot Program.

Additional Information

1For the purposes of this guidance, references to oncology drug products include both human drug products and biological drugs products regulated by CDER, unless otherwise specified. This pilot is currently only available for certain oncology drug products within CDER.


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