The introduction of ADCs into frontline ovarian cancer treatment creates a new challenge: conflicting biomarkers. A patient's tumor might be positive for both HER2 (an ADC target) and a BRCA mutation (a PARP inhibitor target), forcing clinicians to choose between two effective targeted therapies without clear guidance.

The traditional six-month timeframe for defining platinum sensitivity is being challenged. A growing theory suggests that tumors progressing while on a PARP inhibitor have a distinct biology that responds poorly to subsequent platinum, indicating a potential need to move directly to therapies like ADCs.

Real-world data shows that in platinum-sensitive ovarian cancer patients who have progressed on PARP inhibitors, subsequent platinum-based chemotherapy has a surprisingly low response rate of only 20%. This quantifies a significant opportunity for highly active ADCs to potentially replace platinum in this growing patient population.

The widespread use of PARP inhibitors has altered tumor biology in platinum-sensitive ovarian cancer. A recent meta-analysis of heavily pretreated patients, 97% of whom had prior PARP inhibitor exposure, revealed an objective response rate to subsequent therapy of only 17%—far lower than historical expectations, highlighting a critical unmet clinical need.

Unlike early ADCs requiring high biomarker expression (e.g., mirvetuximab), next-generation agents show efficacy even in low-expressing tumors. This allows for broader, "all-comer" clinical trial inclusion criteria instead of biomarker-gated entry, potentially expanding patient access to these novel therapies.

Patients whose ovarian cancer progresses on the folate-targeted ADC mirvetuximab may still respond to a subsequent folate-targeted ADC with a different cytotoxic payload. This suggests that the folate receptor alpha target remains viable and that resistance may be payload-specific, opening new sequencing strategies.

A new wave of antibody-drug conjugates (ADCs) is transforming ovarian cancer treatment. These 'heat-seeking missiles' deliver potent chemotherapy payloads directly to tumor cells, achieving response rates from 23% to over 60% in biomarker-selected populations. This far surpasses the efficacy of conventional chemotherapy in resistant settings.

The REJOICE trial for an ADC in ovarian cancer exemplifies a critical trend: embedding multi-arm dose optimization studies. This approach identified a dose that maintained high response rates (57%) while significantly lowering rates of serious adverse events like ILD (from 6% to 3%), prioritizing patient safety.

Historically, therapies for platinum-resistant ovarian cancer were so ineffective that the order of administration was irrelevant. With the advent of multiple active ADCs, the concept of treatment sequencing and potential cross-resistance based on payloads or targets has become a critical, and entirely new, clinical consideration for this disease.