QLS5132, an investigational CLDN6-targeting antibody-drug conjugate, showed clinical benefit in patients with heavily pretreated platinum-resistant ovarian cancer in a Phase I study presented at AACR 2026. The trial enrolled 28 patients and tested multiple dose levels. Investigators reported treatment-related adverse events in most patients, with nausea, anorexia, anemia, and weakness among the most common. Grade 3 or higher events occurred in about a third of patients, with hematologic toxicities accounting for most of the severe events. No treatment discontinuations or deaths were reported. After a median follow-up of 2.2 months, nine patients achieved partial responses across dosing cohorts. The data positions CLDN6-directed ADCs as a potential next option for a population with limited therapies and limited durable response expectations.