The rise of companion diagnostics (CDx) has undeniably ushered in a transformative era for precision medicine. With close to 200 tests approved by the US Food and Drug Administration (FDA), these tests play a crucial role in matching patients with tailored treatments. While most approved CDx are primarily employed for oncology applications, there is growing interest and ongoing development of CDx for conditions such as cardiovascular, neurological, infectious, autoimmune, and rare or orphan diseases.

These tests are essential for ensuring that only patients with specific genetic or molecular biomarkers receive targeted therapies, maximizing both efficacy and safety, but they also introduce added complexity to the drug development process. In addition to the already demanding workflows of drug discovery and development, pharmaceutical and biotech teams must now allocate time and resources to develop and validate a bespoke diagnostic to accompany their therapeutic. As a result, many are turning to external partners for diagnostic assay development and regulatory expertise to support submissions across multiple global regions.

Taken together, these challenges highlight the growing value of partnering with an experienced diagnostic development partner. Experts in diagnostic biomarker assay development can manage every stage from discovery and design to validation and regulatory review. Through collaborative co-development, CDx and therapeutics can advance in parallel, with clinical trials strategically structured to collect data for both, guaranteeing synchronized market readiness for both products.

However, not all diagnostic developers provide the same level of expertise or end-to-end capabilities. Selecting a reliable partner requires careful consideration of several key factors.

What makes a great partner?

When evaluating potential diagnostic development partners, considering everything from cost to proven success, the following attributes are the most likely to result in a productive and durable alliance.

A long-term relationship: CDx development should never be viewed as a one-off project; there are simply too many twists and turns in the drug development process for this to be an effective strategy. Instead, assay developers should support the pharmaceutical team from early biomarker strategy and pre-IND filing through to clinical trials and eventual commercialization. Beware of any diagnostic developer that promises flat project rates or rigid timelines — this could signal a lack of experience with the complexities involved.

Deep experience: Look for a partner that has developed clinical assays for all phases of drug development. Assay developers with the right track record will do more than create a test: they will offer strategic counsel and understand the linkage of the clinical biomarker to the drug and the patient. An experienced diagnostic partner will develop the assay to the required quality standards, tailor it to the biomarker’s specific clinical utility, and ensure the development process is appropriately budgeted for the optimal assay type.

Broad expertise across diverse biomarker types: Partnering with an assay development company that specializes in nucleic acid diagnostics may suit your needs if your early-stage assays and CDx focus on nucleic acids — but what happens if a more effective biomarker emerges later in development, such as a soluble protein? Biomarkers can vary widely, encompassing nucleic acids, proteins, circulating tumor cells, exosomes, among countless other possibilities. To ensure your diagnostic partner can support your drug program from start to finish, choose a team with proven expertise across a broad spectrum of biomarker types.

Clinical testing capabilities: Unless the drug developer plans to oversee assay and diagnostic testing throughout clinical and commercial stages, it’s important to find a partner equipped to manage those processes. A partner that offers both reagent kit manufacturing and clinical testing capabilities can help establish clear commercial agreements, avoiding future licensing complications and potential market barriers. Beyond running assays in a CLIA environment, such partners can provide deep insight into the acceptability of clinical workflow, helping to mitigate post-market challenges and support broad clinical adoption for a particular CDx.

Regulatory expertise: One of the most frustrating setbacks in CDx development is creating a successful assay only to discover that your diagnostic partner lacks the knowledge to navigate approval requirements in key regions. Regulatory frameworks like the IVDR are complex and require deep expertise — something that cannot be quickly acquired when time is of the essence. Choose a partner with a proven track record of securing regulatory approvals in major markets and who can proactively identify potential market access challenges. Experienced partners make strategic decisions and build in flexibility to accommodate evolving clinical needs and expanding regional interests throughout the drug development process.

Market access and global distribution: Many approved CDx tests are integrated into large liquid biopsy NGS panels that require processing in a central laboratory. While this model is acceptable in the US, it’s far less feasible for patients based outside the country, particularly due to difficulties in transporting clinical samples across borders. This is where a partner’s commercialization expertise is important. Capabilities such as kitted liquid biopsy solutions that can be easily deployed to regional labs enable testing closer to patient enrollment sites worldwide. Additionally, a partner experienced in kit manufacturing can advise on the most suitable technologies for your assay; for example, complex NGS tests may face reimbursement hurdles in some regions, whereas assays using widely adopted platforms like plate readers or PCR could facilitate broader implementation.

Checking for all these attributes while selecting a diagnostic development partner can boost the effectiveness and productivity of the relationship and help to ensure that the right assays are used for the right drug candidate at the right time.

This article was contributed by Erica Frew, senior product manager for companion diagnostics at Bio-Techne.