Scientific Leadership
Anti-Drug Antibodies: Clinical Implications and the Importance of Robust Immunogenicity Testing
By Ester Lopez, Senior Scientist
Understanding the potential of a biotherapeutic to trigger an unwanted immune response is a fundamental part of the drug development process. This response, known as immunogenicity, results in the production of anti-drug antibodies (ADAs) which can significantly impact a drug’s pharmacokinetics, pharmacodynamics, safety and efficacy. These ADAs harbour the risk of mediating unwanted biological or physiological effects, either by inhibiting the effect of the biotherapeutic itself or by provoking adverse events.
Clinical Implications of ADAs
The effect of ADAs induced by a biotherapeutic can vary from no clinical effect to severe, life-threatening responses. Some ADA responses are transient with often no significant effect on drug efficacy or safety. While others are persistent, potentially causing long-term impacts on efficacy and patient outcomes.
A variety of factors can influence the type of ADAs induced by a biotherapeutic. These include drug structure, patient-related factors such as underlying disease and immune status, and treatment-related factors such as route of administration and treatment duration.
Types of ADAs
There are two forms of ADAs: Binding ADAs and Neutralising ADAs. Binding ADAs bind to the drug often without affecting its function. They may still lead to increased drug clearance or impact drug distribution. Neutralising ADAs – a subset of binding ADAs – directly interfere with the drug’s biological activity by blocking its binding to the drug target.
Functional Effects of ADAs
There are several effects of ADAs. These include:
- Reduced efficacy of the biotherapeutic
- Adverse events such as hypersensitivity or autoimmunity
- Alteration of drug absorption, distribution, metabolism, and elimination, leading to subtherapeutic or toxic levels
- Cross-reactive ADAs may neutralise endogenous proteins structurally similar to the biotherapeutic.
Given these potential impacts, early and comprehensive assessment of ADA responses, including their prevalence, type, titre, and impact on clinical outcomes, is essential for optimising the design, safety and administration of biotherapeutics.
Developing Effective ADA Assays
As a partner in ADA testing, our role is to help ensure that therapeutics entering clinical trials are safe. To do this, we develop and validate highly sensitive, regulatory-compliant assays that can report immunogenicity early in the drug development or clinical trial pathway.
Our assays are developed in line with FDA guidelines to achieve the recommended sensitivity of at least 100 ng/ml, as previous studies suggest that ADA concentrations as low as this may lead to clinical manifestations. This sensitivity ensures we don’t miss any ADA responses. Additional assays may be conducted to characterise ADA neutralising capacity, isotyping, cross-reactivity, and other characteristics.
We use a three-tiered approach to examining ADAs in clinical samples:
- Screening: An assayis developed based on the unique therapeutic to screen the samples for any detectable ADA responses. These screening assays use a 5% false-positive rate to maximise the detection of true positives.
- Confirmatory: Samples that test positive in the initial screening are progressed to a confirmatory assay to demonstrate that the ADAs are specific to the therapeutic under investigation, and not a result of a non-specific interaction with another component of the assay. This gives us confidence that the signal in the screening assay is a true positive.
- Titration: Titration assays are then conducted to characterise the magnitude of the ADA response. The clinical effect of ADAs may be associated with their titre rather than the presence or absence of a response, so it’s important to get this qualitative assessment.
Challenges in ADA Assay Development
Developing ADA assays may present potential challenges due to the diverse nature of biotherapeutics, and the potential for biological technical limitations.
Some examples include:
Drug Interference: where there is a high level of circulating drug, with high levels of the biotherapeutic in the serum interfering with ADA detection by competing with the assay reagents for binding to ADAs. Furthermore, ADAs can form complexes with the drug and its target, complicating their detection.
Assay Sensitivity: Sensitivity is key to detecting early ADA responses or low-titre ADAs. However, detecting low levels of ADAs in the presence of excess drug or endogenous proteins is often technically challenging.
Pre-existing Antibodies: Natural antibodies or pre-existing anti-drug antibodies can confound assay results.
Because each therapeutic has a different target, mechanism of action, and potential impact on the immune system, the design of ADA assays requires a tailored approach to achieve accurate and clinically relevant results, which includes robust validation practices, and alignment with regulatory standards to ensure accurate and reliable ADA detection.
Crux Biolabs: Industry-Leading Expertise in ADA Assay Development
At Crux Biolabs, we recognise that developing immunoassays isn’t a one-size-fits-all approach. Our scientists work with clients early on to understand their assay needs, using their extensive experience in immunology to deliver bespoke solutions. This expertise is critical, especially when it comes to troubleshooting any study-specific challenges.
We use the highly sensitive electrochemiluminescence (ECL) Mesoscale Discovery (MSD) platform, to develop our ADA assays, exploring the most suitable and sensitive assay format for the assay, e.g. the bridging or direct assay.
An additional benefit of working with Crux Biolabs is our rigorous quality environment. ADA assays are developed, validated and reported in compliance with FDA and GCLP guidelines, meaning clients can trust their results meet the highest quality standards.
Featured case study: A client recently came to us to assess the ADA response to a new drug they were developing. The drug was a biosimilar to a protein that our bodies produce in high levels, creating a unique challenge—binding of the ADAs to the endogenous protein prevented us from detecting the ADAs using standard approaches. Using our team’s expertise, we developed a novel approach to remove the endogenous protein from the sample prior to ADA evaluation, and this was validated through our rigorous development pipeline. The end result was an assayable to reflect the drug’s immunogenicity accurately and allowed the client to move forward with their clinical testing. This is just one example of how we can apply our deep knowledge of immunology to tackle study-specific challenges.
Why choose Crux Biolabs for your ADA assays?
Developing assays for detecting and characterising ADAs is a complex process that involves multiple challenges. At Crux Biolabs, we use our team’s extensive expertise in immunology to create innovative solutions and overcome many of these challenges. Combined with our scientific expertise, our focus on robust validation practices, and alignment with FDA and GCLP regulatory standards, Crux Biolabs delivers accurate and reliable ADA detection to ensure patient safety and therapeutic efficacy, all fundamental aspects of a successful clinical trial.
Contact us today to learn more about how we can help accelerate your research.
