Sonesitatug vedotin, a claudin 18.2 (CLDN18.2)-targeting antibody drug conjugate (ADC), improved overall survival in phase 3 CLARITY-Gastric01 for advanced or metastatic CLDN18.2-positive gastroesophageal cancer. Results presented at ESMO Congress 2026 showed median OS doubled to 10.0 months from 5.0 months in the third-line-or-later setting. Progression-free survival did not significantly improve in the overall population, leaving the benefit concentrated in later-line efficacy. Trial results were based on 532 patients, with investigators reporting OS gains without a corresponding PFS signal in the primary endpoint structure. The readout supports further positioning of CLDN18.2 ADCs in specific treatment sequences and reinforces the importance of endpoint selection and line-of-therapy stratification in ADC development.