FAQs
Companion Diagnostics & Biomarker Strategy

Q11: What is a companion diagnostic and how is it regulated by the FDA?

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A companion diagnostic (CDx) is a medical device that provides information for the safe and effective use of a corresponding drug or biological therapy. Often the diagnostic will verify a biomarker, such as a gene or protein. 

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Depending on the therapeutic context, the CDx may identify how patients will react to specific therapy. This could include patients who would benefit or, on the other hand, be at increased risk of treatment-related adverse effects. A CDx might also support treatment monitoring for the biomarker when it is essential for safety and effectiveness. 

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CDx are defined by the ability to detect a biomarker and the relationship to the corresponding therapy. The FDA generally expects the therapy and the CDx to be co-developed, reviewed, and authorized together when the test is essential to the therapy’s safe and effective use.

Regulation is dependent on the device classification, intended use, technology, and evidence. The clinical evidence standard for CDx is high. The FDA expects prospective clinical data demonstrating that the biomarker-positive population achieves the therapeutic benefit described in the drug labeling, with pre-specified endpoints and analysis plans.

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Landrich Group supports CDx developers from regulatory strategy through FDA submission, with specific expertise in FDA pre-submission meeting preparation, designing and executing analytical and clinical studies, and preparing PMA, 510(k), or Technical Dossier regulatory submissions. The Landrich Group is assisting NIH with a multicenter 9-year CDx study with multiple tiers or treatment arms. 

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