Strategies for Co-Development of Therapeutics and Companion Diagnostics

The Evolution of Co-Development in Precision Medicine

Precision medicine aims to deliver the right treatment to the right patient at the right time. This goal has fueled the rise of companion diagnostics (CDx), which are laboratory tests or in vitro diagnostics (IVDs) used to identify patients who are likely to benefit from a specific therapeutic product. To meet regulatory expectations and ensure market access, the co-development of drugs and companion diagnostics is now the gold standard.

According to the FDA’s guidance, co-development involves simultaneous clinical and regulatory development of both the drug and the diagnostic test. The European Medicines Agency (EMA) also supports this approach through its integration of the In Vitro Diagnostic Regulation (IVDR) into the centralized drug approval process. This article outlines the key steps, challenges, and best practices for successful co-development.

Why Co-Development Matters

Launching a therapeutic without an approved CDx limits its market reach, delays treatment for eligible patients, and risks non-compliance with global regulations. Co-development ensures that both products are ready for simultaneous approval, which is particularly important for targeted oncology, rare diseases, and immunotherapies.

Benefits of co-development:

• Optimized patient selection during trials
• Stronger clinical evidence for biomarker utility
• Aligned regulatory review timelines (NDA/BLA and PMA)
• Reduced time to market

Example: HER2 testing and trastuzumab (Herceptin) were co-developed, setting the regulatory precedent for modern CDx programs.

Co-Development Workflow and Milestones

Effective co-development requires strategic alignment between drug sponsors and diagnostic partners across development phases. Below is a simplified timeline:

Co-development depends on early assay design decisions, such as the sample matrix (e.g., FFPE, blood), detection method (e.g., NGS, IHC), and anticipated regulatory classification.

Collaborative Models and Legal Agreements

Drug and diagnostic co-development typically involves separate companies. As such, collaborative models must be clearly defined, often through:

• Joint Development Agreements (JDAs)
• Clinical Trial Agreements (CTAs)
• Data sharing protocols
• IP ownership and licensing terms

Successful collaborations clarify roles in assay design, validation, regulatory filing, post-marketing surveillance, and commercial distribution.

Clinical Trial Considerations in Co-Development

When co-developing a drug and CDx, the diagnostic assay must be integrated into the pivotal clinical trial. Key trial design elements include:

• Enrichment or stratified design based on biomarker status
• Assay lock prior to trial initiation
• Validated sample collection and processing SOPs
• Concordance studies if changing assay format between phases

For example, a PD-L1 assay used in an immuno-oncology trial must demonstrate consistent expression quantification and predictive performance before it can be relied upon for regulatory decisions.

Regulatory Requirements: FDA and EMA

The FDA classifies CDx as Class III devices requiring Premarket Approval (PMA), submitted concurrently with the New Drug Application (NDA) or Biologics License Application (BLA). Sponsors must coordinate closely with the Center for Devices and Radiological Health (CDRH) and Center for Drug Evaluation and Research (CDER).

• FDA Requirements:
• Investigational Device Exemption (IDE) for using CDx in trials
• PMA with analytical and clinical validation data
• Labeling alignment between drug and diagnostic

The EMA oversees CDx under the In Vitro Diagnostic Regulation (IVDR). A notified body assesses the diagnostic while EMA evaluates the drug. Coordination is facilitated through joint scientific advice.

Bridging Studies and Analytical Equivalence

If the assay used in the clinical trial differs from the final commercial version, a bridging study is required to demonstrate equivalence. Parameters assessed include:

• Sensitivity and specificity
• Cut-off concordance
• Lot-to-lot variability
• Inter-lab reproducibility

These studies ensure that patients tested with the marketed assay will receive the same clinical interpretation as those in the pivotal trial.

Coordinated Submission and Labeling Alignment

One of the most critical steps in co-development is ensuring synchronized submission of the drug and diagnostic. The therapeutic product label must reference the companion diagnostic, and the diagnostic IFU (Instructions for Use) must include the specific drug indication.

FDA and EMA both require tight integration of regulatory documentation, including:

• Shared clinical trial data (Module 5)
• Analytical validation reports
• Risk management and post-approval surveillance plans

Explore detailed submission checklist templates at PharmaSOP.in.

Commercialization and Post-Market Surveillance

Once approved, both drug and CDx must maintain post-market performance. This includes:

• Ongoing QC testing of the assay
• Real-world effectiveness monitoring
• Adverse event reporting for both drug and diagnostic
• Label updates based on emerging data

In the EU, CDx manufacturers must report performance issues to both the notified body and competent authority under IVDR Article 82.

Challenges in Co-Development

Despite its advantages, co-development presents challenges:

• Misalignment of development timelines between drug and diagnostic
• Cross-border regulatory complexity (FDA vs EMA)
• Sample scarcity for rare biomarkers
• IP and commercial agreement disputes

Early planning and risk-based prioritization are essential to mitigate these issues.

Conclusion

The co-development of drugs and companion diagnostics is central to advancing personalized medicine. Sponsors must foster early collaboration between clinical, regulatory, and diagnostic teams, align trial designs, and synchronize regulatory submissions. A proactive co-development strategy not only streamlines approval timelines but also maximizes therapeutic impact for biomarker-defined patient populations.