Safety and efficacy of BAT8006, a folate receptor α (FRα) antibody drug conjugate, in patients with platinum-resistant ovarian cancer: Update on the dose optimization/expansion cohort of BAT-8006-001-CR trial.

5517 Background: This report presents an update results of the BAT-8006-001-CR trial, which evaluated the safety and clinical activity of BAT8006, an antibody drug conjugate (ADC) consisting of a humanized anti-folate receptor alpha (FRα) monoclonal antibody linked to the topoisomerase I inhibitor exatecan, in patients with platinum-resistant ovarian cancer (PROC). Methods: Patients with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer received BAT8006 monotherapy every 3 weeks. The adverse events, incidence of dose interruptions or reductions, tumor response, progression-free survival (PFS) and overall survival (OS) were determined. Results: As of January 1st, 2025, 131 PROC patients were enrolled across various cohorts: 1.8 mg/kg (n=2), 2.1 mg/kg (n=16), 2.4mg/kg(n=15), 84 mg/m 2 (n=50) or 93mg/m 2 (n=48) cohorts during the dose escalation and dose optimization/expansion study. The most common treatment-emergent adverse events (TEAEs) were anemia (82%), leukopenia (80%), neutropenia (77%), vomiting (67%), nausea (60%) and thrombocytopenia (55%). The most frequent grade ≥3 treatment related adverse events (TRAEs) were neutropenia (42%), leukopenia (33%), anemia (30%) and thrombocytopenia (26%). Notably, no cases of interstitial lung disease (ILD), ocular toxicities, or treatment-related deaths were reported. In the 84 and 93 mg/m 2 dose cohorts, selected for further exploration in the dose optimization/expansion study, the incidences of grade ≥3 neutropenia, anemia and thrombocytopenia were 35% vs 45% ,20% vs 32% and 18% vs 32%, respectively. Among 108 efficacy-evaluable patients with PROC (regardless the FRα expression and prior lines of treatments), the objective response rate (ORR) was 32.4% (35/108) and disease control rate (DCR) was 75.9% (82/108). The median PFS was 6.9 months (95% CI: 4.3-7.9), while the median OS was not reached (NR). In cohort 1 (n = 77), PROC patients with ≤3 lines of prior systemic anti-tumor therapies and FRα expression ≥1% were randomly assigned to received BAT8006 at 84 mg/m 2 (n=40) or 93mg/m 2 (n=37) every 3 weeks. Among 64 efficacy-evaluable patients in this cohort, the ORRs were 30.6% (11/36) and 32.1% (9/28) for the 84 mg/m 2 and 93mg/m 2 doses, respectively, while the DCRs were 75.0% (27/36) and 78.6% (22/28). The median PFS were 7.5 months (95% CI: 4.0-NR) and 5.5 months (95% CI: 2.9-NR), respectively. The median OS were NR. Conclusions: The safety profile is consistent with previous results, with no reports of ILD or ocular toxicity. The preliminary efficacy of BAT8006 appears promising in PROC patients with FRα expression ≥1%. On the basis of these findings, the target population, dose and schedule have been identified for a phase III trial of BAT8006 monotherapy in PROC patients. Clinical trial information: NCT05378737 .