Biopharmaceuticals with immune-mediated effector functions have become increasingly specific and potent when compared with naked monoclonal antibodies. As a result, the commercial interest in antibody drug conjugates (ADCs), bi-specifics, bioconjugates, and fc-fusion-based drugs, has grown in recent years. The latter example involves genetically engineering cells so that the antibodies they produce have an increased or decreased effector function (depending on the desired effect), or a longer serum half-life. The key is being able to understand whether you’re making changes that deliver the right properties – and that requires analytics. Indeed, generating high quality data is vital to the development of all of these emerging drugs. With ADCs, there are several challengs. ADCs are made up of an antibody, which targets the antigen or biomarker of interest, and a linker with a toxic payload attached. The antibody is internalized within the target cell, and releases the drug substance. Finding the right antibody, which tends to be more robust than classical antibodies, means screening for the right physiochemical properties, which affect glycosylation, reactive sites, stability and aggregation. Overall, the process conditions are more challenging for ADCs than for antibodies because you have to consider the antibody–drug conjugation reaction in addition to purification. You also need to control the drug antibody ratio (DAR) – a critical quality attribute for ADCs because it essentially defines the potency. It is also important to check these different properties at the beginning, middle and end of every step in the process.
The right tools in the toolbox
To address all of the above challenges, and when screening for “manufacturability” at an early stage, you need the right analytical tools. Of course, you can use classical chemical techniques, such as RP-HPLC, HIC, analytical IEX, or size exclusion chromatography, when looking at aggregates, DAR, and so on, but there are limitations. Newer techniques, such as surface plasmon resonance (SPR), can provide many benefits such as rapid analysis to address productivity needs and unique insight into binding events. One unique aspect of Biacore’s SPR-based platform is the binding information it provides. You can monitor critical binding kinetics and conduct epitope mapping to characterize antibody structure/function throughout the entire workflow, from candidate selection to comparability assessment, to check the effects of, for example, linker on the function of the antibody. You can also ensure each modification made to the molecule doesn’t affect binding, and look at ADC binding in lysosomal pH. It’s a good starting point before looking at the potency of the molecule in a bioassay. There are often multiple pathways that cause disease, and another emerging drug format, bi-specifics, allows two of those pathways to be targeted at once. In fact, blocking two target proteins with one single drug molecule instead of two may be more efficient as it can change the development timeline and, potentially, the dosing requirements. SPR-based assays allow you to assess the binding activity of bi-specific antibodies in a single setup, with either a bridging assay or dual-binding assay. The SPR-based assays are usually superior to other immunoassays in terms of precision, accuracy and specificity. These factors allow for stability studies, for example, to be carried out in real time – instead of hours or even days. They can also indicate function loss in a parallel analysis of both interactions at the same time rather than with two different ELISA-based immunoassays.The Biacore system can be used as a “platform” technology, from early drug discovery through to quality control, even for more complex drugs. In other words, there is no need to perform any technology transfer between different assay formats, making validation and characterization easier, thus accelerating the time to market. Newer forms of complex biologics have great promise, but at the expense of added complications, whether the conjugation reactions in ADC production or the need to simultaneously monitor multiple reactions in bi-specifics. There is a clear need to measure critical quality attributes from beginning to end – and how they affect binding. And that’s where the SPR-based platform is at its strongest; it can provide molecular interaction data that guides the design of therapeutics with the desired binding properties, all the way from target selection to final quality control. Fredrik Sundberg is Global Director for Strategic Customer Relations and Market Development at GE Healthcare. GE, GE monogram and Biacore are trademarks of General Electric Company.
Newsletters
Receive the latest analytical science news, personalities, education, and career development – weekly to your inbox.
