Vixen Bio is a functional immunology and bioanalytical company in Ghent, Belgium. We help biotech and pharmaceutical teams understand how therapeutic antibodies and other immune-modulating molecules behave in biologically relevant conditions.
We combine real-time binding kinetics, native-matrix measurements and functional immune-cell assays to support candidate selection, mechanism-of-action studies, preclinical development and translational research. Rather than forcing every question onto one technology, we select the analytical approach around the biological question and the development decision.
Our work connects molecular interactions with immune function: antibody–protein and antibody–cell binding, affinity and avidity, Fc receptor engagement, FcRn interactions, cytokine responses, and autoantibody and anti-drug antibody characterization. Assay design and sample suitability are defined for each project.
How can I measure antibody binding kinetics directly in serum or plasma?
Antibody behaviour in purified buffer can differ from its behaviour in human serum, plasma or on cells. Competing proteins, target presentation and other components of complex biological matrices can change the interactions being measured.
Vixen Bio characterizes real-time molecular interactions in native or biologically relevant matrices. Comparing buffer and native-matrix measurements can help investigate whether antibody binding affinity, specificity or candidate ranking is maintained in a different biological environment. The appropriate controls depend on the target, analyte and sample.
Applications include therapeutic antibody characterization, candidate comparison, biomarker interactions and translational bioanalysis. Sample options include serum, plasma, whole blood and cell-based systems, with compatibility assessed for the selected assay.
How can I compare therapeutic antibody candidates beyond affinity?
Affinity describes the strength of an individual binding interaction. Binding kinetics describe how quickly an interaction forms and dissociates; avidity reflects the combined effects of multiple binding interactions. These measurements answer related but different questions.
Candidate characterization can combine affinity, avidity and kinetics with Fc receptor engagement and functional immune responses. Depending on the mechanism of action, relevant readouts may include antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), complement-dependent cytotoxicity (CDC) and cytokine release.
Connecting molecular and functional measurements provides additional evidence for lead selection and lead optimization. A strong binding result alone does not establish the efficacy or safety of a therapeutic candidate.
Read our application note on target and functional affinity during antibody candidate selection.
How can I measure Fc receptor engagement?
Fc gamma (Fcγ) receptor interactions contribute to antibody effector functions. Vixen Bio can characterize interactions with FcγRI, FcγRII and FcγRIII using real-time binding measurements and, where relevant, connect those results with functional immune-cell assays such as ADCC and ADCP.
This helps compare candidates and investigate differences between molecular binding and cellular activity. Receptor subtype, assay format and cellular context are considered when interpreting the results.
What can FcRn binding tell me about antibody half-life?
The neonatal Fc receptor (FcRn) contributes to the recycling of immunoglobulin G (IgG) antibodies and influences their pharmacokinetic behaviour. Measuring FcRn binding and release under different pH conditions can help compare candidates and investigate properties relevant to recycling.
FcRn binding alone does not establish an antibody’s half-life in humans. Other processes, including target-mediated drug disposition (TMDD), can also affect exposure and clearance. We interpret FcRn measurements within the wider characterization question, alongside target binding and relevant functional evidence.
What if SPR results and cell-based assays disagree?
Differences between surface plasmon resonance (SPR) measurements and cell-based results are not necessarily experimental failures. They may reflect differences in receptor density, avidity, target presentation, competing proteins, matrix effects, Fc receptor interactions or downstream cellular mechanisms. Assay design and technical controls also need to be checked.
Vixen Bio combines molecular interaction analysis with functional immune assays to investigate these differences. For antibody–cell interactions, the development question may concern binding kinetics, receptor occupancy or the relationship between target engagement and a functional response. We define the measurements needed to distinguish those questions.
How can I characterize anti-drug antibodies beyond a positive or negative ADA result?
Detecting anti-drug antibodies (ADAs) does not by itself describe their biological relevance. Kinetic characterization can add information about binding behaviour and affinity, potentially complementing conventional immunogenicity assays.
Questions about neutralizing activity, antibody subclass or functional effects require suitable additional assays; they cannot be inferred from a binding-affinity result alone. Vixen Bio develops approaches to investigate antibody responses in biologically relevant samples, with the analytical strategy defined around the specific question.
A related example is our work on autoantibodies: a peer-reviewed study with Vixen Bio-affiliated co-author Sarah Parmentier investigated anti-double-stranded DNA (anti-dsDNA) antibody kinetics and disease severity in systemic lupus erythematosus (SLE). This is an autoantibody study, rather than validation of a therapeutic ADA assay.
Read the peer-reviewed anti-dsDNA antibody kinetics study or our accompanying scientific article.
How can functional immunology support candidate selection?
Candidate selection often requires integrating several biological dimensions. Vixen Bio can combine molecular interaction data, native-matrix behaviour, Fc receptor engagement and functional immune responses to compare candidates and investigate why their behaviour differs.
Projects may involve monoclonal antibodies (mAbs), single-domain antibodies (sdAbs), including VHH antibodies often called nanobodies, bispecific antibodies or T-cell engagers. The relevant readouts depend on the molecule’s intended mechanism of action (MoA). The objective is to provide evidence for a defined development decision.
Can functional immune profiling support clinical development?
Functional immune profiling can complement conventional biomarker measurements by investigating changes in immune behaviour during treatment. Depending on the biological question, longitudinal samples can be evaluated using binding, immune-protein, cytokine and cellular functional measurements.
Exploratory analyses can support mechanism-of-action hypotheses, biomarker development and interpretation of patient-to-patient differences. Their use for patient stratification, disease monitoring or prediction of treatment response requires evidence appropriate to that intended use.
Which analytical methods can contribute to the answer?
Depending on the project, the analytical approach can include label-free interaction analysis using SPR or fibre-optic SPR (FO-SPR), enzyme-linked immunosorbent assays (ELISA), Luminex multiplex protein profiling, fluorescence microscopy, fluorescence-based antibody–cell binding kinetics and functional immune-cell assays.
These methods provide different kinds of evidence. We select and combine them according to the target, sample matrix, required readout and development question, rather than treating any single technology as a universal solution.
Do I need to know which assay I need before contacting Vixen Bio?
No. Many projects start with a biological or development question rather than a predefined assay. For example:
- Why do these two candidates behave differently?
- Will the candidate ranking remain the same in human serum?
- Does humanization change binding properties relevant to recycling?
- Which candidate should we take forward, and what evidence is missing?
- Does the candidate trigger the intended—or an unintended—immune response?
- Why does our functional assay differ from our binding data?
- What changes in the immune response during treatment?
We translate the development question into an analytical strategy and determine which combination of molecular, biochemical and cellular measurements is appropriate.