IMMUNOGENICITY
CASE STUDY
Background
Antibody-drug conjugates are among the most structurally complex therapeutics in development today. By linking a monoclonal antibody to a potent cytotoxic payload via a chemical linker, ADCs combine targeted delivery with high-potency cell killing. That structural complexity, however, creates a specific challenge for immunogenicity assessment that standard anti-drug antibody approaches are not designed to address.
The FDA and EMA have both stated that immune responses to multi-domain proteins, including ADCs, must be characterised with respect to each functional domain. A patient may develop antibodies against the antibody backbone, the linker-payload component, or both, and each response carries different implications for drug safety, efficacy, and pharmacokinetics. Understanding which domain is driving an immune response requires a testing strategy built around the molecule’s architecture, not just its overall structure.
The Challenge
A single bridging ADA assay cannot distinguish between an immune response directed at the antibody backbone and one directed at the drug-linker component. For sponsors advancing ADCs into clinical development, this means a standard immunogenicity package is insufficient to meet regulatory expectations.
Developing and validating the multiple assay formats needed to characterise domain-specific responses requires significant scientific expertise, appropriate critical reagents, and experience across a range of ADC architectures. Not all CROs have built this capability. For sponsors, choosing a partner without it creates real regulatory risk at a stage in development where delays are costly.
Ready to Characterise Your ADC’s Immune Response?
Resolian partners with leading pharma and biotech companies to deliver validated immunogenicity assays
for ADCs and complex multi-domain biologics.
Our Approach
Resolian’s UK Bioanalytics team has developed a tiered ADA testing framework specifically designed for ADCs and other multi-domain proteins, including bispecifics, fusion proteins, and PEGylated molecules. The approach characterises immune responses at each functional level of the molecule:
- Screening: whole ADC assay.
A bridging immunoassay uses labelled ADC as both capture and detection reagent, identifying samples with anti-drug or anti-linker antibodies against the intact conjugate. - Confirmatory: whole-molecule assay.
Unlabelled ADC is used as the competitor. Samples containing anti-backbone or anti-drug/linker antibodies show signal reduction, confirming the presence of ADAs against any domain of the intact molecule. - Confirmatory: backbone-only assay.
Unlabelled antibody backbone (without payload) is used as the competitor. Only samples with antibodies directed specifically at the antibody backbone show signal reduction, allowing domain-specific characterisation. - Positive control strategy.
Positive controls can be a polyclonal antibody raised against the whole molecule, or a mixture of monoclonal antibodies targeting different epitopes across the ADC domains, depending on what is available and scientifically appropriate for the programme.
All assays are developed and validated in line with GCP and GLP standards, with method development, project management, and biostatistics teams working in coordination across the full lifecycle.
What We Devliery
Resolian’s ADC immunogenicity programme delivers:
- A validated screening assay for the intact ADC, with appropriate sensitivity, drug tolerance, and cut point established
- A validated confirmatory assay at the whole-molecule level
- A validated backbone-specific confirmatory assay, enabling domain-level characterisation of immune responses
- A positive control strategy appropriate to the molecule and programme stage
- Full GCP/GLP-compliant documentation, supporting regulatory submission throughout the method lifecycle
- Ongoing sample analysis support from method development through to clinical study completion
What This Means
For sponsors developing ADCs, having a validated immunogenicity package that meets FDA and EMA expectations for multi-domain characterisation removes one of the more complex regulatory uncertainties in clinical development. It means submissions can be made with confidence that immune responses have been properly characterised at the domain level, and that the data will withstand regulatory scrutiny.
It also means that if an immune response is detected, the programme has the tools to understand what is driving it, which domain is implicated, and what the implications are for continued development. That kind of clarity is what allows teams to make informed decisions rather than reactive ones.
Resolian partners with leading pharma and biotech companies to deliver validated immunogenicity assays for ADCs and complex multi-domain biologics. Learn more about our immunogenicity capabilities.
Ready to Characterise Your ADC’s Immune Response?
Resolian partners with leading pharma and biotech companies to deliver validated immunogenicity assays for ADCs and complex multi-domain biologics.
