AstraZeneca (LSE/STO/NYSE: AZN) said its experimental drug sonesitatug vedotin (Sone-Ve) met the primary endpoint of a Phase III clinical trial, showing a statistically significant improvement in overall survival in patients with CLDN18.2-positive advanced gastric and gastroesophageal junction (GEJ) cancers.

The CLARITY-Gastric01 trial evaluated Sone-Ve as a second and later-line therapy in patients whose tumors expressed the CLDN18.2 protein in at least 25% of cells. The trial met its dual primary endpoint of overall survival in third and later-line treatment, and a key secondary endpoint of overall survival in the broader second and later-line patient population, both versus investigator's choice of therapy.

The trial's other dual primary endpoint, progression-free survival as assessed by blinded independent central review, showed a trend toward improvement but did not reach statistical significance.

AstraZeneca said Sone-Ve was well tolerated with no new safety signals identified. The company said the data will be presented at a forthcoming medical meeting and shared with global regulatory authorities.

Sone-Ve is an antibody drug conjugate (ADC) that targets CLDN18.2 with a monomethyl auristatin E payload. AstraZeneca licensed the drug from KYM Biosciences in March 2023. It has received Orphan Drug Designation from the U.S. Food and Drug Administration and the European Commission for gastric and GEJ cancers, and Breakthrough Designation in China for second-line gastric cancer treatment.

The trial was conducted across 175 centers in 19 countries. An estimated 60% of gastric and GEJ cancers express CLDN18.2 in 25% or more of tumor cells, according to the company. Roughly 183,500 patients in the U.S., EU, China, and Japan are treated annually in the second and later-line setting for advanced CLDN18.2-positive, non-HER2-positive gastric and GEJ cancers.