A new investigational antibody-drug conjugate that targets claudin 18.2 has been shown to double overall survival in patients with heavily pretreated gastroesophageal carcinoma, according to data presented from a recent phase III trial. The median overall survival for participants who received the experimental therapy, identified as sonesitatug vedotin, reached ten months, whereas those who continued on standard-of-care options survived for roughly half that time.
Survival at the one-year mark also favored the experimental arm, with 38.1% of those patients still alive compared with 18.1% among the control group. Although the study did not achieve its second primary goal of improving progression-free survival as assessed by an independent review, it succeeded in meeting a key secondary objective that measured progression-free survival among individuals receiving treatment in the third line or later.
Study Details
The trial, named CLARITY-Gastric01, represents the first global phase III investigation to demonstrate a statistically meaningful gain in overall survival together with a manageable safety profile for a claudin 18.2-directed ADC in a population of previously treated, advanced or metastatic, claudin-positive gastroesophageal cancer. Rui-Hua Xu, MD, PhD, from Sun Yat-sen University Cancer Center in Guangzhou, China, delivered the results at the European Society for Medical Oncology meeting held in Madrid.
Dr Xu emphasized that the drug produced a statistically significant and clinically relevant improvement in overall survival when compared with investigators’ choice of therapy, and this benefit was observed both in the third-line-or-later cohort and across the broader intention-to-treat population. Moreover, the survival advantage persisted across subgroups defined by varying levels of claudin 18.2 expression.
Expert Analysis
During the session, ESMO invited discussant Salah-Eddin Al-Batran, MD, of the Frankfurt Institute of Clinical Cancer Research, described the findings as impressive. He highlighted that the median survival more than doubled, rising from five months with standard therapy to ten months with the ADC, and that the hazard ratio fell below 0.5, indicating a substantial reduction in the risk of death.
Al-Batran also cautioned that combining patients who received the conjugate in the second line with those treated later makes interpretation more complex. When second-line participants are included, the overall-survival benefit remains positive but appears less striking, suggesting that the pronounced advantage seen in the broader second-line-and-beyond group may be driven largely by individuals treated in the third line or later.
Treatment and Safety
The study featured dual primary endpoints: progression-free survival in the intention-to-treat cohort and overall survival among patients receiving therapy in the third line or beyond. The intention-to-treat group comprised 594 randomized individuals, with a median age of 57 years.
Grade 3 or higher adverse events possibly related to therapy occurred in 36.4% of those given the experimental agent, compared with 44.8% in the comparator arm. Treatment discontinuation because of adverse events was reported in 3.1% of the experimental group versus 4.4% among controls.
The investigational ADC pairs an anti-CLDN 18.2 antibody with a microtubule-disrupting payload. Investigators enrolled patients who had received second-line therapy or later for advanced or metastatic disease and whose tumors displayed claudin 18.2 expression on at least a quarter of cells, as determined by membrane staining.
Dr Xu noted that conventional second-line therapy for gastroesophageal cancer typically yields a median overall survival of less than ten months, which further declines to under six months when patients move to third-line options. Approximately forty percent of gastroesophageal tumors express claudin 18.2, yet no therapy targeting this protein has obtained global approval for use beyond the first line.
The primary analysis revealed a fifty-three percent reduction in the hazard of death for patients receiving the ADC. In the intention-to-treat population, a secondary assessment of overall survival showed a median of ten point six months with the experimental drug, contrasted with six point four months for the standard therapies.