# Companion Diagnostics in Clinical Therapy: Current Applications and Future Directions

## TL;DR

Companion diagnostics help tailor cancer treatments to individual patients using biomarkers, improving effectiveness and reducing costs, but face challenges like test standardization and resistance mechanisms.

## Contribution

This review provides a comprehensive overview of CDx development, challenges, and future directions, emphasizing multiomics and AI integration.

## Key findings

- CDx is critical in oncology for targeting therapies based on biomarkers like EGFR and HER2.
- Challenges include tumor heterogeneity, test standardization, and economic barriers to co-development.
- Future trends involve AI, multiomics, and next-generation diagnostic platforms like liquid biopsies.

## Abstract

Companion diagnostics (CDx) plays a pivotal role in precision medicine by enabling personalized treatment plans based on individual biomarker profiles. This approach can enhance therapeutic efficacy in selected indications and may reduce healthcare expenditures. Particularly in oncology, precision targeted therapies targeting pathways such as EGFR, HER2, and programmed death‐1/programmed death‐ligand 1 have established robust models for biomarker‐driven treatment. However, rapid advancements in diagnostic technologies, expanding application scopes, and increasingly complex mechanisms of biomarker resistance are presenting new challenges for CDx. This review comprehensively examines the evolving regulatory landscape, current clinical applications across various solid tumors and hematologic malignancies, and diverse methodological platforms ranging from next‐generation sequencing and immunohistochemistry to emerging liquid biopsies and point‐of‐care testing. It also delves into persistent barriers in CDx development, including tumor heterogeneity, test standardization, trade‐offs between tissue biopsy and liquid biopsy, and the economic complexities of codevelopment and reimbursement mechanisms. By synthesizing existing knowledge and projecting future trends, this paper serves as a valuable resource for researchers, regulators, and clinicians. It provides critical insights to guide the synergistic development of drugs and diagnostics, paving the way for their integration into a more dynamic, artificial intelligence‐enhanced, and multiomics‐driven healthcare ecosystem.

Companion diagnostics use biomarker‐based assays to stratify patients for precision therapies, improving outcomes while reducing ineffective treatment and side effects. This review summarizes the evolution, regulatory landscape, clinical applications, and technological platforms of CDx, highlighting their role in biomarker‐driven precision therapy. It outlines current challenges and emphasizes future directions, including multiomics integration, AI‐enabled interpretation, and dynamic, next‐generation CDx development. Created with BioRender.