Sonesitatug vedotin, a claudin 18.2 (CLDN18.2)-targeting antibody-drug conjugate, posted a clinically meaningful overall survival improvement in the phase 3 CLARITY-Gastric01 trial, presented at the ESMO Congress 2026. In the third-line-or-later cohort, median OS doubled to 10.0 months versus 5.0 months with investigator’s-choice therapy. Progression-free survival (PFS), however, did not significantly improve in the overall intention-to-treat population, leaving the benefit profile concentrated in later-line survival outcomes. Trial results were reported for 532 patients with unresectable, locally advanced or metastatic CLDN18.2-positive gastroesophageal carcinoma. The study enrolled patients based on membranous CLDN18.2 staining (at least 25% tumor cells with any intensity). After initial randomization across two sone­sitatug vedotin doses and investigator’s-choice, the study settled into a comparison between sone­sitatug vedotin 2.2 mg/kg and investigator’s choice for newly enrolled patients. For drug developers, the readout strengthens CLDN18.2 as a late-line target while underscoring that endpoint selection may determine where ADC value is most evident for regulatory and commercial strategy.