AstraZeneca's sonesitatug vedotin (CMG901, AZD0901) has demonstrated a statistically significant and clinically meaningful overall survival (OS) benefit in second- and later-line CLDN18.2-positive advanced gastric cancer, according to top-line Phase III results disclosed by China-based partner Lepu Biopharma Co. (HKEX: 02157). The readout from the CLARITY-Gastric01 global Phase III trial marks the first randomized Phase III evidence of an OS benefit for a CLDN18.2-directed ADC in this setting, where no biomarker-selected therapy currently holds approval.
The trial enrolled 594 patients with locally advanced or metastatic gastric cancer, gastroesophageal junction cancer, or esophageal adenocarcinoma expressing CLDN18.2 on at least 25% of tumor cells at any staining intensity, conducted across 175 centers in 19 countries. The design carried dual primary endpoints: OS in the third- and later-line population and PFS by blinded independent central review in the overall 2L+ population. The OS endpoint in the 3L+ population was met, and a key secondary endpoint of OS in the broader 2L+ population also reached statistical significance. The PFS primary endpoint did not achieve statistical significance, though a trend toward improvement was observed. The safety profile was described as consistent with the known profile of sonesitatug vedotin, with no new signals identified. No quantitative data — median OS, hazard ratios, or p-values — were disclosed in the top-line announcement.
Sonesitatug vedotin is an ADC comprising an anti-CLDN18.2 antibody linked via a cleavable linker to MMAE, a microtubule-disrupting payload. Upon binding CLDN18.2 on tumor cell surfaces, the conjugate is internalized and MMAE is released intracellularly, inducing mitotic arrest and apoptosis. CLDN18.2 is selectively overexpressed in approximately 60% of gastric and GEJ adenocarcinomas, making it an actionable tumor-restricted target.
The only approved CLDN18.2-directed therapy is Astellas's Vyloy (zolbetuximab-clzb), which gained FDA and EU approval in 2024 for first-line HER2-negative disease in combination with chemotherapy. Zolbetuximab is a naked antibody that works through ADCC and CDC rather than cytotoxic payload delivery, and it holds no approval in the 2L+ setting. The CLARITY-Gastric01 data therefore position sonesitatug vedotin in a line of therapy entirely uncontested by any approved CLDN18.2-targeted agent. In the 2L+ non-CLDN18.2-selected setting, Eli Lilly's Cyramza (ramucirumab) plus paclitaxel remains the standard backbone, offering modest survival benefit without biomarker selection.
The drug was co-developed by KYM Biosciences — a joint venture 70% owned by Keymed Biosciences (HKEX: 02162) and 30% by Lepu Biopharma — and licensed to AstraZeneca in February 2023 under a global exclusive agreement. AstraZeneca has previously projected peak sales for sonesitatug vedotin of between USD 3.0 billion and USD 5.0 billion. The molecule holds Breakthrough Therapy Designation from China's Center for Drug Evaluation, as well as Orphan Drug and Fast Track Designations from the US FDA.