Surface Plasmon Resonance Molecular Interactions and Ligand Binding Analysis
Melanie Verneret, PhD, Molecular Bioanalytical Scientist, SGS Vitrology, Glasgow, UK
Characterisation of therapeutic monoclonal antibodies, drugs and other biological products is a necessary step required during the regulatory approval process. The manner in which biopharmaceuticals and therapeutic antibodies interact and bind with the target molecule is one important aspect of this characterisation requiring analysis.
When ligand binding is part of the functional activity of a biosimilar or therapeutic product, FDA and EMA guidelines require this property be quantified1,2. Binding assays are essential to defining immunological properties and biological activity of monoclonal antibodies3,4,5,6,7.
Efficient selection, optimisation, and characterisation of bio-therapeutics are essential throughout the development process, as well as for understanding molecular mechanisms and structure-function relationships. An efficient development process is crucial to identifying important aspects of product performance and to provide confidence in selection.
Furthermore, determining concentration and monitoring kinetic data during drug-substance stability studies and batch production are key elements for quality control of manufacturing biotherapeutics.
The GMP compliant BiacoreTM T200 system is an established and state-of-the-art instrument for real-time and label-free biomolecular interaction analysis and binding assays. The system is used to deliver high-quality kinetic, binding affinity, concentration, specificity, selectivity, and thermodynamic interaction data, all with high sensitivity. Based on Surface Plasmon Resonance (SPR) technology, the Biacore T200 system significantly enhances performance so that the upper and lower limits of kinetic ranges can be assessed. Moreover, the system enables analysis of interactions between biomolecules ranging from low molecular weight ions to complex viruses. This powerful system has a wide variety of applications from biological research, vaccine development, bio-therapeutics and small molecule drug development, through to immunogenicity studies and quality control 8.
The Biacore T200 system can be used to address a multitude of scientific questions. For example, do two biomolecules interact and, if so, how specific is the interaction? What are the kinetic parameters for this interaction? How strong is this interaction (ie, affinity)? How fast is the duration of the interaction (ie, rate constants for association and dissociation)? What is the active concentration of a specific biomolecule?
Answers to these important questions can be achieved by determining the binding affinity constant (KD), association rate (ka), and dissociation rate (kd). Such studies are often limited by low sample concentrations, but Biacore T200 achieves accurate results where other systems cannot. The Biacore T200 yields data on association kinetics with a sample concentration ≥10 pM and with an association rate (ka) ranking from 103 to 3 x 109 M-1 s-1 for protein or 103 to 5 x 107 M-1s-1 for low molecular weight molecules and a dissociation rate (kd) from 10-5 to 1 s-1.
Typically, this data can be obtained with the antibody of interest immobilized onto the surface of the sensor chip. Using this configuration, the Biacore T200 was used to determine association, dissociation rate and affinity (Figure 1).
The Biacore T200 can also be used to obtain precise information regarding the specificity of an interaction. Using a capture strategy, antibody specificity can be assessed using a range of antigen concentrations from two species (Figure 2). In this experiment, the data demonstrates the antibody has a higher affinity for antigen from one species over another, demonstrating that, in this situation, the antibody/antigen interaction is very specific.
The Biacore T200 system can be used for custom development services and method validation in compliance with GLP or GMP, thus ensuring accurate and consistent analysis of all samples. The applications of this system are many and have been performed in our laboratories include:
- Screening applications:
- Clone and candidate selection with ranking of binding affinity constant, as well as association and dissociation rates
- Screening of putative binding partners
- Quantitative kinetic evaluation (quality control release & stability):
- Binding affinity constant, and association and dissociation rates
- Relative binding assessments and consideration of biosomilar molecules
- Antibody characterisation:
- Antibody isotype determination
- Immunogenicity assessments, such as Anti-Drug Antibody measurements (ADA)
The SGS Vitrology team is highly experienced in the capabilities of the Biocore T200. This system has been qualified and validated in our laboratories and is a routinely used tool for rapid timelines and cost-effective solutions for many types of studies and a broad range of applications.
- ICH Topic Q 6 B Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products (1999).
- FDA Draft Guidance for Industry, Quality Considerations in Demonstrating Biosimilarity to a Reference Protein Product (2012).
- FDA Point to consider in the manufacturing and testing of monoclonal antibody products for human use (1997).
- FDA Guidance for Industry Monoclonal Antibodies Used as Reagents in Drug Manufacturing (2001).
- The European Pharmacopoeia - Monoclonal antibodies for human use (current edition).
- Guideline on development, production, characterisation and specification for monoclonal antibodies and related products, EMEA/CHMP/BWP/157653/2007.
- Guideline on similar biological medicinal products containing monoclonal antibodies – non-clinical and clinical issues, EMA/CHMP/BMWP/403543/2010.
- GE Healthcare, Biacore T200 product description. Retrieved Jan 28, 2014.