Companion Diagnostics (CDx) — Bridging Laboratory Tests and Targeted Therapies
A Companion Diagnostic is an IVD device that provides information essential for the safe and effective use of a specific drug. This "co-development" of a drug and its diagnostic test is the bedrock of 2026 oncology.
For instance, before a patient can receive Trastuzumab (Herceptin) for breast cancer, an IVD must confirm that their tumor overexpresses the HER2 protein.
This document details the regulatory pathway for CDx, where the FDA or EMA requires clinical evidence that the drug only works (or is significantly safer) in the "biomarker-positive" population. This shift reduces the "trial and error" approach in medicine, saving the healthcare system billions of dollars in ineffective treatments and protecting patients from unnecessary side effects.
