ADC conjugation process

Conjugation is the step at which antibody, linker, and payload are assembled into the final ADC construct. The drug-to-antibody ratio (DAR) is determined here and directly impacts therapeutic window, pharmacokinetics, and tolerability. Precise control of pH, redox state, and reagent concentration is required to achieve homogeneous conjugates meeting defined quality specifications.

Find reagents for the ADC conjugation workflow stage.

• Biological buffers for antibody-payload conjugation
• Detergents for payload solubilization
• Redox reagents for thiol stabilization
• Stabilizers for aggregation prevention

Find a variety of crosslinkers:

• Biotin-based crosslinkers
• DBCO-based crosslinkers
• BCN-based crosslinkers
• Cathepsin cleavable crosslinkers

Biological buffers for antibody-payload conjugation

Precise pH and ionic strength during antibody-payload conjugation directly influence reaction efficiency and conjugate homogeneity. Tris and sodium citrate buffers provide stable conditions for reproducible conjugation, minimizing DAR variability and preventing degradation of pH-sensitive linker intermediates. 

Detergents for payload solubilization

ADC payloads can sometimes have limited aqueous solubility that can impede conjugation efficiency and reproducibility. Non-ionic and mild ionic detergents facilitate payload dispersion at sub-micellar concentrations, enabling homogeneous reaction conditions without disrupting antibody structure.

Redox reagents for thiol stabilization

Partial reduction of interchain disulfide bonds generates free thiols for cysteine-maleimide conjugation. Glutathione (reduced and oxidized forms) supports controlled thiol management, enabling selective reduction and facilitating re-oxidation where needed to preserve structural disulfides while maintaining payload attachment sites.

Stabilizers for aggregation prevention

Aggregation of antibody or conjugate intermediates during reaction can compromise DAR uniformity and reduce overall yield. Excipients such as sucrose and sorbitol act as preferential exclusion stabilizers, maintaining the hydration shell around proteins and reducing the thermodynamic drive for aggregation throughout the conjugation process. 

Biotin-based crosslinkers

Biotin-PEG crosslinkers are used in ADC workflows primarily for analytical characterization, enabling site-specific labeling, antibody capture, and purification via streptavidin/avidin affinity systems. The PEG spacer improves aqueous solubility and minimizes steric interference, supporting consistent performance in detection and immobilization applications.

DBCO-based crosslinkers

DBCO crosslinkers enable copper-free strain-promoted azide-alkyne cycloaddition for site-specific ADC conjugation. By reacting selectively with azide-functionalized antibodies or payloads, they generate stable triazole linkages without the cytotoxicity of copper catalysts, making them well-suited for bioorthogonal conjugation strategies.

BCN-based crosslinkers

BCN-based crosslinkers deliver site-selective, bioorthogonal conjugation via Strain-Promoted Azide-Alkyne Cycloaddition (SPAAC) without the need for copper catalysts. Their compact, high-ring-strain scaffold reacts rapidly with azide-tagged payloads, while BCN's superior hydrophilicity over bulky DBCO minimises aggregation risk with hydrophobic ADC payloads. The maleimide variants enable either single-cysteine attachment (mono-bromo) or disulfide rebridging (di-bromo), delivering homogeneous DAR ~4 constructs with full antigen-binding retention. The pyridazinedione variants covalently rebridge reduced cysteine thiols, restoring disulfide structural integrity while introducing a stable payload attachment point.

Cathepsin cleavable crosslinkers

Val-Cit-PAB cathepsin-cleavable linkers are cleaved by lysosomal cathepsin B following ADC internalization, triggering intracellular payload release at the tumor site. This mechanism is among the most clinically validated ADC linker designs, incorporated in approved therapeutics such as brentuximab vedotin.

Discover our complete range of crosslinkers.