FAQ Antibody Screening, Microfluidics What is a droplet-based microfluidic system? The general idea is to distribute a sample into several thousand individual “reaction chambers”. By using microfluidic technology the sample can be encapsulated into so-called water-in-oil droplets in an automated way. What are the general advantages of droplet-based microfluidics? There are several advantages of droplet-based microfluidics compared to other high-throughput screening systems. Most of all, the miniaturized volumes enable to obtain detectable concentrations of antibodies from individual cells, paving the way for large scale screens using primary, non-immortalized cells. Furthermore, due to the low sample consumption, reagents costs are massively reduced, too. What is unique about VERAXA’s antibody screening compared to other microfluidics approaches? VERAXA has unique and proprietary droplet assays enabling to measure very transient cell-signaling events upon receptor binding of an antibody. Despite signals lasting only seconds, we can screen millions of antibody secreting clones for such properties. What benefit does your technology for therapeutic antibody development offer to pharma companies? Our droplet-based microfluidic screening enables the rapid identification of antibody candidates with functional modulatory capabilities, thus supporting a true ‘function first’ approach. By exclusion of target-binding, but non-functional antibodies early on, the number of candidates for characterization and further engineering can be focused on high-potentials, thus reducing time and effort of lead candidate identification. What kinds of antibody sources can be used? A microfluidic screening can be performed with all kinds of antibody secreting cells. Usually, these are plasma cells isolated from organs of immunized animals. In addition, blood of a patient or disease survivor can be implemented. In principle, cells secreting antibodies of a synthetic library may also be applied. What is the size of the droplets? The size if the droplets and thus the reaction volume can be adjusted to individual needs. Typically, the diameter is in a range between 10 µm and 150 µm, resulting in a volume of 0.5 pL to around 2 nL. Are immune cells that secret the antibodies immortalised or modified in any way? No. To preserve the whole immune repertoire and assure that as wide pool of mAbs as possible is being analysed the cells used for screening are primary cells and are being analysed directly after harvesting from donors/animals. What types of readouts can be translated into VERAXA microfluidic system? Almost all cellular readouts based on the change of fluorescent signal can be adapted into our microfluidic platform. Is this system used only for Eukaryotic cells? No. This system can be used also for screening of any process in/with bacteria cells or viral infections. What is viability of cells in droplets? Mammalian cells survive with viability around 90% for up to 48 h in the droplets. Prokaryotic cells be cultivated much longer with no adverse effect. What is the main difference between your system and FACS? FACS only allows for sorting of single cells based on the presence of surface or intracellular molecules. VERAXA droplet based microfluidic system is based on sorting of separate assays. Every single droplet can be compared to a multiwell plate well where all the components interact with each other and can be assessed as a single co,partment. This allows to analyse secreted molecules such as antibodies as well as as interactions between different cell types, cell infection by viruses etc. How many parameters can be analysed simultaneously? The detection and sorting units of our workstations are equipped with multicolor laser systems. Up to 4 different wavelength parameters can be analysed simultaniously in a single step. What is the minimally required signal to noise ratio for your system to efficiently sort “true” positive events? Our system requires at least two fold change of fluorescence (as established with conventional techniques e.g. plate reader) to sort with low rate of false positive hits. Antibody Engineering, ADCs, ARCs What is unique about VERAXA’s antibody engineering compared to other approaches? VERAXA proprietary platform for antibody engineering and modification allows for ultrafast, quantitative labeling of antibodies at any specific position, hence producing single species site-specific antibody drug conjugates (ADCs). We introduce unnatural amino acids into the protein chain harboring the chemistry of the fastest biorthogonal click reaction to date. Our labeling technology is applicable in optimal adjusted conditions and can even be applied in vivo. What is the advantage of site-specific ADCs? On top of the batch-to-batch reproducibility, the site-specific attachment of payloads allows for modulation and improvement of the pharmacokinetics of the ADC and contributes to a wider therapeutic window. How many labeling positions can be implemented? We do routinely 2-4 per antibody, but more are possible. Which antibodies can you modify? Our platform relies on implementation of our proprietary unnatural amino acids into the protein via genetic code expansion. Therefore, only proteins that can be recombinantly expressed can be considered. Can you modify other proteins or peptides as well? Of course. Similar to as stated above, any protein that can be recombinantly expressed can be modified through our platform. Are you really completely free in your choice of position? Theoretically yes. We modify the antibody sequence and therefore can implement this in any given position. However, there might be unprecedented factors impairing expression of proteins with some modifications. Nonetheless we have experience in choosing optimal positions which will work fine. Which expression systems do you use? We work with insect cell as well as mammalian cell-based expression systems to cover non-glycosylated as well as glycosylated antibodies. Can I choose a specific drug-to-antibody ratio (DAR)? Sure. We have solutions available to cover DARs of approaching 2, 4 and 8 molecules per antibody. Which payloads are available? We try to provide the majority of common ADC payloads, i.e. Auristatins and Maytansinoids, with a variety of cleavable or non-cleavable linkers, as well as chelators for therapeutic and imaging radioisotopes. But feel free to contact us about specific payloads, which we probably can implement into our platform for you.