Antibody Drug Conjugates
Antibody Drug Conjugates continue to play a central role in cancer treatment and immune-based therapeutics.
Our Antibody Drug Conjugates Services help sponsors characterize biological activity and therapeutic potential through:
These studies provide the evidence needed to advance the most promising antibody candidates.
Pre and Post Conjugation Characterization
Antibody–drug conjugation transforms a well-characterized antibody into a far more complex molecule — and that transformation is not always neutral. Conjugation can introduce steric hindrance around the Fab, impact epitope accessibility, and alter Fc conformation, affecting interactions with Fc receptors and complement. The result is often a shift in binding affinity, potency, and effector function that cannot be predicted from the naked antibody alone.
We address this by performing comprehensive pre- and post-conjugation characterization, ensuring you understand exactly how your antibody behaves before and after payload attachment.
Pre-conjugation, we establish a clear baseline for the unconjugated antibody — including target binding affinity, specificity, potency, and Fc-mediated functions. This creates a reference framework against which all post-conjugation changes are measured.
Post-conjugation, we systematically re-evaluate the ADC to detect even subtle functional shifts. Using platforms such as the Sapidyne KinExA 4000 for high-resolution affinity measurement and ELISA for screening and comparability, we assess whether conjugation has altered true binding characteristics. In parallel, we perform cell-based potency assays and effector function studies (ADCC, ADCP, CDC) to understand how structural changes translate into biological activity.
Critically, we compare all key parameters side-by-side:
Fc Functions
Effector functions are often the difference between a molecule that binds and a molecule that works. In immuno-oncology, Fc-driven mechanisms like ADCC, ADCP and CDC directly translate target engagement into tumor cell killing or clearance — and poor understanding here is a common reason why otherwise strong binders fail to deliver in vivo.
We evaluate these mechanisms using both flow cytometer-based assays and the IncuCyte S3, allowing you to capture not just endpoint activity but the kinetics of immune-mediated killing in real time. This dual approach helps distinguish fast-acting vs sustained responses, subtle potency differences, and donor-dependent variability — all critical for selecting the right candidate.
Our ADCC and ADCP assays are built around physiologically relevant systems, combining target cells with effector populations such as PBMCs/NK cells or macrophages, with flexible assay design depending on your program stage. We support both stable fluorescent labeling (GFP/mCherry) and industry-standard cytotoxicity/cell labeling dyes, enabling precise tracking of target cell fate, phagocytosis events, and immune cell engagement.
For CDC, we design assays tailored to your biology — including both cell-based complement-mediated cytotoxicity models and biochemical formats where appropriate, depending on whether you are assessing functional lysis or complement activation potential.
The goal is simple: move beyond “does it bind?” to “does it recruit the immune system effectively?” — and generate data that actually predicts in vivo performance.
Antibody Internalization
For ADCs, binding alone is not enough — efficacy depends on whether the antibody is internalized and whether the payload is released inside the cell. This is where many otherwise strong molecules fail.
We assess antibody internalization and payload release using the IncuCyte S3, enabling real-time tracking in live cells without disturbing the system. Using Sartorius IncuCyte® reagents specifically designed for these assays, such as pH-sensitive dyes (pHrodo®-based), we directly monitor internalization as the antibody–antigen complex traffics into acidic compartments like endosomes and lysosomes — a key step for ADC processing.
In parallel, payload activity is captured using IncuCyte apoptosis and cytotoxicity reagents, allowing us to link internalization kinetics with functional outcome in the same experiment. We also support stable GFP/mCherry-tagged target cells or antibody labeling strategies to ensure precise and continuous tracking.
This approach provides a clear, time-resolved understanding of whether your molecule simply binds, or actually enters the cell, reaches the right compartment, and releases payload effectively — which is ultimately what drives ADC success
DAR Impact
Drug–antibody ratio (DAR) is a critical determinant of ADC performance, influencing both binding and cytotoxicity. While increasing DAR can enhance payload delivery, it can also introduce steric hindrance around the Fab region, alter antibody conformation, and reduce epitope accessibility — ultimately impacting binding affinity and consistent target engagement.
These structural and functional changes translate directly into biological outcomes. Lower DAR may limit payload delivery and reduce cytotoxic effect, whereas higher DAR can compromise binding, internalization, stability, and Fc interactions — leading to suboptimal efficacy despite higher drug loading.
We systematically evaluate DAR impact by comparing target binding, internalization, and cell-based potency across ADC variants, ensuring selection of a construct that maintains the optimal balance between affinity, payload delivery, and overall therapeutic efficacy.
Bystander Killing Assay
Bystander killing is where ADCs reveal their true potential — or their risk. In heterogeneous tumors, not every cell expresses the target, so the ability of a payload to diffuse and eliminate neighboring antigen-negative cells can significantly enhance efficacy. At the same time, uncontrolled bystander effect can raise safety concerns. Understanding this balance early is critical.
We evaluate bystander killing using mixed co-culture systems of antigen-positive and antigen-negative cells, tracked in parallel using the IncuCyte S3 and flow cytometer. Target and non-target populations are distinctly labeled — either through stable GFP/mCherry tagging or with cell-specific fluorescent dyes — enabling clear, simultaneous monitoring of both populations within the same well.
With IncuCyte, we continuously visualize how killing propagates over time — starting from antigen-positive cells and extending (or not) to neighboring antigen-negative cells. This real-time view reveals the onset, spread, and extent of bystander effect, which static endpoint assays often miss. Flow cytometry complements this with high-resolution quantification, confirming population-specific killing and validating assay outcomes.
This combined approach allows you to clearly answer:
Does your ADC kill only target-expressing cells, or does it extend its effect to surrounding cells?
