Biomarkers are critical to drug development. Disease-related biomarkers can indicate the potential risk of developing a disease, such as using cholesterol as a biomarker for heart disease.

Whereas, diagnostic biomarkers can inform whether a patient has a particular disease, such as using bilirubin as a biomarker to identify a genetic disorder. And, finally, prognostic biomarkers can determine the feasibility of a therapy and its ability to alter or mitigate disease progression, such as a patient with HER2-positive breast cancer as a candidate for chemotherapy Herceptin.

With this utility, it should come as no surprise that 45 percent of drug approvals are based on surrogate endpoints — biomarkers intended as substitutes for clinical endpoints to determine whether a treatment works1. These endpoints are typically used when clinical outcomes might take too long to study. For example, a trial testing a statin to prevent heart disease in patients with high cholesterol could use cholesterol (the biomarker) as the surrogate endpoint — rather than waiting 20 years or more to observe whether a patient had a cardiovascular event. While they are not true indicators of how well a therapy will work, the use of biomarkers as surrogate endpoints in clinical trials is critical to gaining early approval of new drugs to treat serious or life-threatening diseases.

Another application for biomarkers is in precision medicine. An example of this would be where a biotech or pharma company co-develops an in vitro diagnostic (IVD) assay — in this case, a companion diagnostic (CDx) — for a biomarker that can help determine the best patient population for a therapeutic drug, which will be marketed along with the CDx.

That said, there are some considerations that need to be taken into account before assay development can proceed: For one thing, biomarker assays used in bioanalytical settings have different standards and requirements than those used in Clinical Laboratory Improvement Amendments (CLIA)-certified clinical labs. Further complicating this is the fact that certain biomarker methods may require full biomarker analytical validation, while others, such as a CDx, follow a different standard.

Here we discuss current perspectives on the use of biomarkers, differences between the needs of biomarker assays developed for use in bioanalytical labs or clinical labs, and what may be needed in the case that a biomarker assay needs to migrate into a CLIA lab.

Perspectives on the use of biomarkers

Biomarkers can support a variety of endpoints, including exploratory, primary and secondary. Exploratory endpoints often measure biomarkers as a standard panel, looking for a safety signal or, in other instances, looking for an early efficacy signal. These biomarkers could include cytokine panels, oxidative stress biomarkers or proinflammatory biomarkers.

Primary endpoints are often related to safety and sometimes efficacy, such as in a Phase I trial. Secondary endpoints are typically the pharmacokinetics of the therapeutic (e.g., the clearance of the investigational drug from the patient’s body). Another example is target engagement by the therapeutic. From a precision medicine perspective, the presence or amount of a particular biomarker may be used to stratify a patient population for enrollment into a clinical trial.

Regulatory perspectives and considerations

Regulators have issued expectations on the degree of method validation for biomarker assays for subsequent application of the assay in clinical trials. In 2018, the FDA issued a Guidance for Bioanalytical Method Validation (BMV) and introduced the concept of fit-for-purpose approaches for biomarker methods. The Guidance provides information on the level of validation that may be required depending on the intended use of that data. For example, a pivotal study being submitted for regulatory decision needs the biomarker assay to be fully validated. Whereas biomarker assays being used for exploratory endpoints for internal decision-making only — rather than for a regulatory decision — do not require rigorous method validation.

A process that one might follow for determining the level of assay validation rigor required for a particular biomarker method starts with understanding how the clinical trial assay (CTA) is going to be used. For example, is the CTA being used to:

  • Support a PK/PD correlation
  • Enroll or stratify a patient population into a trial
  • Determine drug safety

If a CTA is being used to measure secondary or exploratory endpoints only, then the method need only be validated as a fit-for-purpose bioanalytical method. If the CTA is being used to support patient response to therapy, but not for direct treatment decisions then the method should be validated in accordance with the FDA Guidance for BMV. However, if the CTA is being used to support a primary endpoint, patient selection, treatment decisions, a safety endpoint, or become an eventual CDx then the method should be validated and applied in a CLIA lab and potentially follow Clinical and Laboratory Standards Institute (CLSI) standards.

Application of biomarker methods in a bioanalytical context, or research use only

Biomarkers are sometimes used for research only or internal decision-making, such as a standard panel of safety biomarkers that is important for a particular therapeutic area. For example, studying arthritis or chronic obstructive pulmonary disease, a researcher may be interested in the presence or absence of certain pro-inflammatory cytokines.

In early phase studies, where the primary focus is on the safety and tolerability of a therapeutic, sponsors might want an early readout of clinical efficacy. And so, in those cases, one might measure a particular biomarker, and then correlate that to therapeutic drug levels. While Phase I studies are often not run to make decisions on efficacy, biomarker data could show target engagement and indicate therapeutic activity, suggesting that the biomarker may become a secondary or even a primary endpoint in subsequent clinical trials.

Bioanalytical methods are also used for exploratory endpoints to answer scientific questions. Some biomarkers might be measured with a commercial kit, for instance, a cytokine panel in a multiplex format.

At the other end of the spectrum are pharmacodynamic endpoints that will be submitted for regulatory decisions, which require full validation. Sponsors will need an analytical method that is shown to be appropriately selective and sensitive while also understanding the stability of the biomarker through the process of collection to analysis. To do this typically requires well-characterised reference standards and as such, this may be a case where commercial kits may not be appropriate for full method validation.

Requirements for a biomarker method transitioning from bioanalytical to clinical

Sometimes biomarker assays initially developed in the bioanalytical lab, later see application in routine clinical use and therefore will need to be transitioned into a CLIA lab.

There are many important factors to consider when reporting results to clinical sites. First, sponsors should ensure that selected laboratories can comply with the minimum federal and state requirements, including CLIA certification. Second, they should determine if industry standard certification is also required, e.g., College of American Pathologists (CAP) accreditation. Further, a laboratory utilising key processes that are consistent with the recommendations of the Clinical Laboratory Standards Institute (CLSI), which provides best practice standards for medical laboratories, may also be warranted.

Next, consider whether to verify or validate. According to definitions by CAP, analytical verification is the process by which a laboratory determines that an unmodified FDA-cleared approved test performs according to the specifications set forth by the manufacturer when used as directed, including accuracy, precision, sensitivity, reportable range and reference range.

Analytical validation is the process used to confirm with objective evidence that a laboratory-developed or modified FDA-cleared/approved test method or instrument system delivers reliable results for the intended application. This is a more extensive process with a focus on establishment over verification. When validating a laboratory-developed test — whether it’s de novo, based on analyte-specific reagents, research-only reagents or investigational use only reagents — the extent of validation should be sufficient to ensure that one has confidence in the results that are released by that laboratory-developed test to a clinical site.

Other factors include risk considerations and clinical validity. For example, will the test provide a direct standalone result that guides a specific therapeutic intervention? Or is this a screening device for serious diseases or conditions intended for use in asymptomatic patients with no other available confirmatory diagnostic product or procedure? In those scenarios, the result provided to the clinical site must be highly accurate, as a failure to do that may result in detrimental events for trial participants.

Maintaining assay quality

Once the validation process of an assay is complete, the quality of the assay must be continually monitored and maintained. This will typically include daily, weekly and monthly monitoring such that labs can ensure ability to control and track the precision and accuracy of the assay.

Quality inputs drive quality outputs. For example, selecting the highest performing assay for a specific analyte may mean choosing an automated assay that typically performs better than a manual benchtop assay. It is also important to establish quality control rules from the start, and that staff are adequately trained on the use and maintenance of the assay.

In addition, it’s important to have acceptance criteria for critical reagents. By ensuring high-quality inputs and monitoring them before introducing to an analytical system, the chances of high-quality analytical data are maximised.

Special considerations for CDx

A CDx can be an IVD or an imaging tool that provides information essential for the safe and effective use of a corresponding therapeutic product. One of the key factors in the co-development of CDx and therapeutic products is to consider the level of validation to be performed on your IVD and the stages at which the validation should be performed. For example, at the preclinical stage, having a highly developed assay may not be necessary. But, when the product has reached the end of its development pipeline, the CDx should be ready for marketing approval and developed to the FDA requirements.

Conclusion: ICON Lab Services approach

Evolving a bioanalytical assay into a CLIA-validated assay begins with strategic planning. Assays can be developed and validated in bioanalytical labs, following FDA Guidance and industry best practices. For routine clinical use, the assay will need to be transferred to a CLIA lab, wherein a laboratory-developed assay is established and then validated to CLIA standards prior to being submitted for health authority approval. If the biomarker is being used as a primary indicator of efficacy and is thought to be crucial for indicating successful therapeutic intervention, then the next logical step would be to collaborate with a commercial vendor to develop custom IVD and CDx assays.

At ICON, we strive to ensure that the biomarker method is capable of creating high-quality analytical data that is complete, precise and accurate because a high quality analytical dataset facilitates an efficient and accurate clinical assessment of the efficacy and safety of the investigational product within the population of interest.

While it is not always a clear decision whether to use an analytical or CLIA lab for biomarker method development and validation, using a strategic, fit-for-purpose approach and partnering with an expert in specialty lab services can provide a path forward.

To learn more about ICON labs visit:

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*CLIA (Clinical Laboratory Improvement Amendments) is a federal requirement for clinical laboratories that establishes quality standards to ensure the accuracy, reliability, and timeliness of patient test results regardless of where the test is performed.

** The Clinical and Laboratory Standards Institute provides standards and guidelines for medical professionals through its unique consensus process.


1. Guidance for Industry: In Vitro Companion Diagnostic Devices and Principles for Codevelopment of an In Vitro Companion Diagnostic Device with a Therapeutic Product