ADCs Are Creating a New Cleaning Validation Problem

Antibody-drug conjugates put a biologic, a chemical linker and a cytotoxic payload on the same equipment train — and each of those three components, plus its degradation products, behaves differently under cleaning. A vendor webinar on 9 July 2026 frames the challenge; independent guidance explains why the traditional single-analyte cleaning strategy no longer answers the question.

What happened

On 9 July 2026, STERIS Life Sciences hosted a complimentary webinar titled "Antibody Drug Conjugate (ADC) Cleaning Validation: Managing Complexity Across the Product Lifecycle," presented by Paul Lopolito (Director, Technical Services) and Brian Bosso (Manager, Technical Services).

As a vendor event, the framing reflects STERIS's position as a supplier of cleaning agents and cleaning-process services. The stated scope is nonetheless specific: ADC products integrate small- and large-molecule components, which increases cleaning validation complexity and "directly impacts cleaning methods, analytical strategy selection and limit setting, particularly for high potency compounds and degradation pathways."

The announced content covered best practices for cleaning individual components and the final conjugate, grouping strategies, analytical method selection, establishment of degradation- and exposure-based limits, and how design-phase insights feed qualification and ongoing monitoring across the cleaning validation lifecycle.

Why it matters

The cleaning validation problem for conventional biologics is already difficult. Alkaline CIP at 0.5–1 N NaOH and 70–80 °C denatures protein, so product-specific immunoassays lose specificity and TOC becomes the primary residue indicator.

ADCs break the assumptions that made that world tractable. As one industry white paper on ADC manufacturing puts it, ADCs consist of three separate active parts — the antibody, the linker and the payload — each with its own cleaning behaviour. A shared-equipment strategy that works for the antibody may be almost irrelevant to a lipophilic auristatin or PBD payload.

Independent evidence is unambiguous about the hazard: HPAPI payloads used in ADCs sit in Category 4 of the SafeBridge-derived occupational classification — the most hazardous category — and Bioprocess International reports that for HPAPI facilities MACO must be below 10 ppm, tighter than for non-potent molecules. Containment and cleaning validation are not separable topics here.

What is particularly interesting

Three things stand out.

First, the analyte list multiplies. Independent LC-MS reviews of ADC bioanalysis show how carefully free payload must be handled: cleavable linkers (vc, disulfide) release payload, and cleavage during sample processing can artificially inflate free-payload results. That same lability makes a cleaning sample a moving target — a swab extract is not necessarily a stable system, and the analyte you quantify may not be the residue that was on the surface.

Second, degradation is a limit-setting problem, not just an analytical one. STERIS's own framing highlights "degradation and exposure based limits." This is consistent with the EMA HBEL guideline, which notes explicitly that for "a therapeutic protein conjugated to a small molecule as pharmacophore (e.g. a cytostatic agent), the toxicity of the conjugate needs to be considered." A PDE derived only for the antibody — or only for the free payload — does not describe the residue risk of the conjugate.

Third, sensitivity may not be the binding constraint. An independent ISPE presentation lists the real pitfalls: critical cleaning parameters, drug product degradation, analytical method recovery factors, air-liquid interface residues, TOC recovery and stainless-steel maintenance. Samsung Biologics, publishing its own cleaning-method development, reports LOQ/LOD values "well below typical ADC residual acceptance limits" — the method is not the hard part; agreeing the limit and proving recovery on the right surfaces is.

What could we learn

• Segment the soil. Treat antibody, linker, free payload, conjugate and degradants as separate residue classes with separate acceptance rationales, not one "product residue."
• Derive limits per component. Exposure-based (PDE) limits need to reflect the conjugate and the free payload as distinct toxicological entities, consistent with EMA HBEL logic.
• Qualify recovery on every material of construction. A single-material or single-analyte recovery study is a documented gap.
• Confirm sample stability. Linker lability means swab/rinse extracts need hold-time data of their own — degradation in the vial is a false-negative risk.
• Grouping needs a defensible worst case. Platform grouping across linker-payload families is attractive economically, but the grouping rationale must show which payload is hardest to clean and most restrictive by PDE.

Questions worth asking in our own programme

• Have we defined the target analyte set for ADC residues explicitly — antibody, linker, free payload, conjugate and known degradants — or are we relying on a non-specific method?
• Is our PDE/HBEL calculation specific to the conjugate and the free payload, or extrapolated from the antibody alone?
• What is our swab and rinse recovery factor on each material of construction, and was it qualified for each analyte class?
• Do we hold sample stability data for cleaning samples of linker-labile products, and does it cover the actual laboratory hold time?
• On shared equipment, what is the worst-case payload by both cleanability and PDE, and is that rationale data-supported rather than narrative?
• Do we rely on visual inspection or a non-specific method anywhere in a cytotoxic changeover?

Wider context

ADC capacity is concentrated in a small number of facilities handling cytotoxic materials. Regulators review ADCs with both large- and small-molecule expertise, and there is still no ADC-specific cleaning guidance — companies must build a defensible position from biologics and HPAPI expectations together. Where data cannot support a threshold value, the EMA guideline points to dedicated facilities rather than a cleaning argument.

Sources

• STERIS Life Sciences (vendor event page, verified 18 Sep 2026): https://www.sterislifesciences.com/Events/2026/July/ADC-Cleaning-Validation
• ISPE, Cleaning Considerations for Antibody Drug Conjugate (ADC) Products: https://ispe.org/webinars/videos/cleaning-considerations-antibody-drug-conjugate-adc-products
• EMA, Guideline on setting health-based exposure limits for use in risk identification in the manufacture of different medicinal products in shared facilities: https://www.ema.europa.eu/en/documents/scientific-guideline/draft-guideline-setting-health-based-exposure-limits-use-risk-identification-manufacture-different-medicinal-products-shared-facilities_en.pdf
• Bioprocess International, Process Challenges of Antibody–Drug Conjugates: https://www.bioprocessintl.com/monoclonal-antibodies/process-challenges-of-antibody-drug-conjugates
• Regulated bioanalysis of antibody-drug conjugates using LC-MS (PMC12087923): https://pmc.ncbi.nlm.nih.gov/articles/PMC12087923/
• Samsung Biologics (vendor white paper, industrial practice): https://samsungbiologics.com/media/science-technology/a-versatile-analytical-approach-to-cleaning-validation-for-multiple-linker-payload-adc-platforms

Vendor claims are labelled as such; independent and regulatory sources are cited for all substantive technical statements.