By Dr. Kurt Sales, CSO
Biomarkers are playing an increasingly important role in clinical studies where they can provide essential efficacy, safety, and pathology data around the drug and indication being investigated. While early-phase first-in-human studies are typically focused on safety in healthy subjects, with pharmacokinetics as the main secondary endpoint, biomarker-based studies can offer crucial insights from the outset. However, the world of Biomarkers can be a minefield to traverse – especially in the context of drug discovery and development and regulated bioanalysis.
What is a biomarker?
A Biomarker can roughly be described as an indicator of biological function or activity or a defined characteristic that is measured as an indicator of normal biological responses, pathogenic processes or a biological response to an exposure. Biomarkers might be therefore be soluble proteins, DNA or RNA, cell populations, or a biological process (e.g., blood pressure).
Mechanism-based biomarkers can provide information on whether the drug is binding its target and can be useful during dose-escalation to help guide effective drug concentrations; provide additional information relating to patient populations to guide stratification of patients in later trials; or identify certain characteristics within responders. Most mechanism-based biomarkers directly relate to the mode of action of the drug.
Clinical biomarkers, such as those routinely analyzed through diagnostic pathology laboratories, can provide useful pharmacodynamic information relating to off-target effects (what the drug has done to the cells, tissues and organs of the subject), potential cytokine storm syndrome, or elevation in liver enzymes and inflammatory markers or blood pressure.
The choice of biomarkers included in clinical studies can thus vary quite widely and this poses a challenge for a bioanalytical laboratory to understand the purpose of the biomarker when setting an assay up and how it fits into the sponsors trial.
How are biomarker assays setup at Agilex Biomarkers for use in clinical studies?
At Agilex, we use a context-of-use (COU) framework for Biomarker assays. The topic of COU has been widely regarded in the industry since as far back as 2011, where bioanalytical bodies like the European Bioanalysis Forum spearheaded the discussions around defining the purpose of the assay for each analyte. Critical to this is understanding the intended use of the assay and the expected biological variability of the analyte and thus understanding the expected outcome of the data, to fully ensure that the chosen assay can provide measurable data and is fit for its intended purpose. The COU is thus a concise description of the biomarkers specified use in drug development and each qualification or validation effort for a biomarker should identify a single COU. More information on COU and its definition can be found on the USA FDA website ( https://www.fda.gov/drugs/biomarker-qualification-program/context-use).
Why is this important? It is important to understand the purpose of the biomarker to guide assay selection at the outset. If for example the purpose of the biomarker, and therefore the COU, was to evaluate treatment response to guide clinical dose escalation, and chosen assay variability is 50% but the expected increase or decrease in nominal concentration of the biomarker is 30-50%, then any changes associated with the drug and therefore evaluation of efficacy would be lost within the assay noise. Under these circumstances a less variable assay would be required in order to provide data of sufficient quality to determine efficacy and fulfil the COU. COU and understanding the assay requirements and how this fits in with the clinical study is thus an import part of the Agilex scoping process for biomarker assays to ensure we craft an appropriate COU statement to support the phase of the assay, select the appropriate assay and define the types of tests that need to be conducted to prove assay robustness. It is also important to ensure the validation strategy is appropriate.
Exploratory setup, Qualification or Validation?
At Agilex, we use a life cycle management process for biomarker assays and the assay is thus tailored to the required context of use. For example, where the expression and variability of the biomarker is unknown, the COU statement might be hard to define over and above the setup of the assay to determine effect upon dosing. This COU might define a basic exploratory setup of a commercial kit – to be used as per the manufacturers’ instruction only to provide information relating to concentration over time.
What is exploratory setup of the assay? Commercially available assay kits typically use recombinant proteins for the standard curve and quality controls (QCs) and these act as a surrogate for the biomarker to be detected. At Agilex, we tend to take the assay a step further by creating endogenous QCs from the matrix of the clinical population and several subjects might be screened in order to find responders that could provide a low, medium and high level to cover sufficient range of the standard curve. This is not always possible as certain biomarkers might be low or undetectable in clinical samples and as such the best we can do is use the kit assay as is. Exploratory assay setups thus comprise tests to measure assay performance in the Agilex lab against the manufacturer’s data. Qualification or validation (often limited really to accuracy and precision and performance of the recombinant proteins) could be performed on these assays as repeated measures of performance and robustness and additional tests such as parallelism and stability can be added in using endogenous QCs, if available. In general most sponsors opt for a basic exploratory setup until they have sufficient data to determine whether the biomarker could be used for efficacy or evaluation of the drugs’ mechanism during the clinical trial before validation. At this point, with sufficient understanding of the biomarker and how it behaves in relation to the drug, the COU of the assay and the intended outcome can be well defined. The COU statement thus changes over the lifecycle of the biomarker in line with the data that it generates. Whether it is exploratory setup, qualification of validation, assays are setup at Agilex to ensure the best possible data for your trial.
With almost 3 decades across regulated bioanalysis including exploratory, qualification and validation of biomarker assays, the Agilex team have considerable experience in setting up assays fit-for-purpose, ensuring the appropriate robustness tests are conducted according to the assays COU to ensure success in the clinic. Contact us today for a confidential discussion on how Agilex can support your biomarker studies.
