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Antibody-Drug Conjugates: Building Clinical Confidence from Design to Patient
How integrated design, translational science, safety, and strategy turn early ADC decisions into reliable clinical outcomes
Antibody-drug conjugates (ADCs) are a compelling prospect in drug development. They combine biological specificity with molecular potency, yet clinical success has not relied on a single breakthrough. Instead, it depends on how well early scientific decisions withstand the transition from design through preclinical testing and into clinical trials.
Our experts explain how ADC development is an interconnected process. They demonstrate how alignment across design, preclinical models, safety assessment, and chemistry, manufacturing, and controls (CMC) enables meaningful comparisons of early data with clinical outcomes and helps teams identify potential challenges before they affect patients.
From Design to First Patients: Where ADC Stories Begin
Every ADC program begins with a biological hypothesis – a target believed to be disease-specific and actionable.
However, the review clarifies that simply binding to a target does not guarantee clinical success. What truly matters is whether binding results in effective internalization, suitable payload release, and controlled exposure.
Very strong binding can hinder tissue penetration, while targets that do not internalize well often lead to poor clinical efficacy, even if they show promising in vitro results. This is why modern ADC design focuses more on a molecule's behavior in a biological system than on its binding affinity alone.
Innovations such as bispecific and biparatopic antibodies, improved linker chemistries, and controlled drug-to-antibody ratios (DAR) are not minor upgrades, but responses to clinical insights from previous ADC generations. Importantly, these design choices influence whether preclinical results can be meaningfully compared to clinical outcomes.
Preclinical Models: The First Translation Test
Preclinical development is a critical phase where ADC hypotheses are either validated or reveal potential risks. The publication stresses that ADCs should not be assessed solely with generic cytotoxicity assays; instead, mechanism-specific in vitro systems are necessary to simultaneously evaluate binding, internalization, cytotoxicity, and bystander effects within a unified biological context.
In oncology, the preference for CDX and PDX models results from practical trade-offs. Although these models vary in biological complexity, the review highlights that efficacy patterns are surprisingly consistent across both, indicating that understanding mechanisms is often more important than the specific model used.
When clinical setbacks occur, they are frequently linked to preclinical issues, including insufficient characterization of internalization, over- or underestimation of bystander effects, or incomplete integration of PK/PD relationships.
Successful ADC programs leverage preclinical data not only to demonstrate activity but also to set expectations that can be tested and improved in clinical trials.
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Safety: When Payload Biology Meets Patient Reality
As ADCs advance towards clinical use, safety testing becomes the primary challenge for validating design assumptions. The review reveals a consistent trend across programs – toxicity mainly depends on the payload, while the antibody influences the occurrence and frequency of adverse effects.
Early failures in ADC clinical trials often result from premature payload release or unexpected exposure profiles not fully predicted preclinically. This issue becomes particularly critical as ADCs extend into areas outside oncology. In life-threatening cancers, regulators tolerate higher toxicity levels and shorter treatment courses. However, for chronic or non-oncology conditions, the safety margin is much narrower.
Therefore, the capacity to compare preclinical toxicology, pharmacokinetics, and initial clinical safety data is crucial. Designing ADCs with clinical tolerability as a priority from the beginning, rather than trying to fix issues after toxicity arises, significantly improves the chances of successful progression into later-stage trials.
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CMC: The Quiet Enabler of Clinical Continuity
Although less visible, CMC underpins the credibility of every clinical outcome.
The review highlights that ADCs challenge traditional manufacturing principles. The antibody, linker, and payload must each be carefully controlled, both individually and as a whole, throughout development.
Without strict oversight of DAR distribution, conjugation consistency, and payload stability, comparisons between preclinical batches and clinical material can be unreliable. This gap may lead to unpredictable variations in exposure, safety, or effectiveness during clinical use.
Conversely, programs that incorporate CMC considerations early on can ensure real comparability among preclinical, toxicology, and clinical studies, minimizing the risk that results are influenced more by manufacturing differences than by biological factors.
The Underlying Message: Continuity Over Silos
This publication ultimately shows that ADC success is not achieved through step‑by‑step optimization, but through step‑by‑step preservation.
- Design choices influence preclinical relevance.
- Preclinical models shape clinical expectations.
- Safety findings confirm (or challenge) early hypotheses.
- CMC determines whether data can be meaningfully compared across phases.
When these elements are aligned, ADC programs move into the clinic with fewer surprises and clearer signals. When they are not, challenges often arise when they are the hardest to address.
Read the Full Open‑Access Review
Koehler C., Herbrand U., Piche M‑S., Schueler J.
Antibody–drug conjugates: from efficacy testing to bioassay evaluation in modern drug development. Drug Discovery Today (2026)