Antibody-Drug Conjugate (ADC) Characterization with MMS
What Are Antibody-Drug Conjugates (ADCs)?
The special class of biotherapeutics known as antibody-drug conjugates (ADC) is distinguishable based on the unique specificity of a monoclonal antibody (mAb) covalently linked to a highly potent drug payload (warhead) by an enzyme cleavable linker. ADCs are efficacious therapeutics in the treatment of oncological diseases as they specifically target certain antigens expressed on the cancer cells. ADCs enable low drug dosages and minimize systemic toxicity because of the specific affinity to the cancer cells and high potency of the warhead. Consequently, ADCs provide more potent chemotherapeutic drugs with a more tolerable side-effect profile for patients. Currently, four ADCs have been approved for use as drug products and many more are in the development and approval pipelines.
Why Structural Characterization Matters for ADCs
Quality production of ADCs involves understanding the structural characteristics of the mAb vehicle and the combined complex itself as they impact specificity and stability of the ADC complex. Thus, there is need for characterizing the antibody portion of the complex pre-conjugation and comparing it with the complex post-conjugation to determine if critical secondary structures within the mAb have changed as they may compromise specific binding to a designated target cancer antigen.
How MMS Technology Supports ADC Analysis
The novel Aurora TX utilizes a quantum cascade laser (QCL) and a microfluidic flow cell to provide secondary structural characterization of the native antibody pre- and post-conjugation via Microfluidic Modulation Spectroscopy (MMS). This unique approach to IR spectroscopy provides confidence in the ‘similarity’ of the conjugated and unconjugated antibodies by comparing their intrinsic IR spectra. The improved sensitivity provided by the QCL and the real time background buffer subtraction powered by the MMS technology enable the ultrasensitive detection of the smallest differences between the native, warhead-free antibody, and the loaded antibody-drug conjugate.
ADC Structural Validation with the Aurora Platform
As an example of the impact of MMS and our first-generation instrument, the AQS³pro, for characterizing ADCs and their native antibodies, we carried out a series of studies in collaboration with Immunogen to demonstrate its use as a tool for ADC development. The ADC conjugating process attaches the drug to unmodified lysine residues across the mAb and the aim of this study was to confirm that the structure of the antibody had remained intact after being conjugated. The secondary structure of both native and conjugated mAbs were measured, and Figure 1 shows that the process of conjugating the warhead to the mAb does not affect the secondary structure. Lastly, the delta software was used to determine the fractional contributions of secondary structural motifs. The results were consistent with no structural change in the mAb before and after lysine-conjugation with the potent payload.
Common Questions About Antibody-Drug Conjugates
What is an antibody-drug conjugate (ADC)?
An antibody-drug conjugate (ADC) is a targeted cancer therapeutic that links a potent cytotoxic payload to a monoclonal antibody through a chemical linker. The antibody delivers the drug selectively to cells expressing its target antigen, concentrating cytotoxicity at the tumor while limiting systemic toxicity.
How is an ADC characterized structurally?
MMS on the Aurora TX measures the secondary structure of the antibody component directly in formulation buffer, without tags or dyes. Because attaching a drug-linker can perturb antibody folding, MMS confirms whether the antibody retains its native higher-order structure after conjugation.
Why does conjugation affect ADC structure?
Attaching hydrophobic drug-linkers to an antibody can destabilize local folding, promote aggregation, and shift the alpha-helix and beta-sheet balance. Detecting these changes matters because structural perturbation can reduce binding specificity, lower efficacy, and increase aggregation or immunogenicity risk.
Can MMS compare an ADC to its parent antibody?
Yes. MMS measures the secondary structure of both the unconjugated antibody and the finished ADC under identical conditions, quantifying any conjugation-induced structural change. This direct comparison supports comparability and developability assessment during ADC process development.
How does MMS support ADC stability studies?
By quantifying changes in beta-sheet content and overall higher-order structure under thermal or formulation stress, MMS detects early aggregation and conformational shifts in ADCs. These insights inform formulation, linker, and storage decisions throughout development.
Biomolecular Structure Analysis
