Data from a novel Nectin-4 ADC trial showed zero responses in patients with prior topoisomerase therapy. This strongly suggests that payload resistance, not just the ADC target, is a critical mechanism that will dictate future treatment sequencing.

The current ADC landscape is saturated with similar drugs using topo-isomerase-1 inhibitors. This creates a market opportunity and an ethical imperative to develop new payloads with different mechanisms of action to treat patients who will inevitably develop resistance to the current generation of therapies.

When sequencing antibody-drug conjugates, clinical experience suggests that resistance to the chemotherapy payload is a primary driver of failure. Therefore, oncologists tend to avoid using another ADC with the same payload consecutively, preferring to switch both target and payload if possible.

As numerous antibody-drug conjugates (ADCs) move to frontline cancer therapy, a key concern emerges: most use a small number of payloads (like topo-1 inhibitors). There is pessimism about whether sequencing different ADCs that share the same payload will be effective.

Retrospective data shows that using one Antibody-Drug Conjugate (ADC) after another, particularly those with the same class of payload like TOP1 inhibitors, results in a low response rate of 10-20%. This creates a significant unmet need and a major clinical challenge for patients who progress on a first-line ADC.

When sequencing antibody-drug conjugates (ADCs) for SCLC, resistance may be driven more by the cytotoxic payload (e.g., a topoisomerase 1 inhibitor) than the antibody's target antigen. This suggests prior exposure to a similar payload class could predict non-response, even when using an ADC with a different target.

Emerging data shows that a second ADC, particularly one with the same payload, often has limited efficacy. This suggests clinicians must be highly strategic in selecting the first ADC, as it may be their most impactful opportunity for this class of drugs.

Most new antibody-drug conjugates (ADCs) for ovarian cancer use the same topoisomerase-1 (Topo1) inhibitor payload. This similarity will likely prevent their sequential use due to cross-resistance, forcing clinicians into a "one-shot" scenario where they must choose the single best Topo1-based ADC upfront for a patient.

As more antibody-drug conjugates (ADCs) become available, a key concern is resistance to the cytotoxic payload. If a tumor develops resistance to a topoisomerase-1 inhibitor from one ADC, it may not respond to other ADCs using the same payload, regardless of their different antibody targets, complicating future treatment sequencing.