AstraZeneca’s experimental cancer drug sonesitatug vedotin, also known as Sone-Ve, has shown an advantage in a late-stage clinical trial involving patients with advanced stomach and related gastrointestinal cancers.
The Phase III study found that patients treated with the drug in the third-line or later treatment setting had a median survival of 10 months. This compared with five months for patients who received the doctor’s choice of treatment.
The results were presented at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid, Spain, on 25 October.
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The findings suggest new hope for patients whose cancer continues to develop despite previous treatments.
AstraZeneca Cancer Drug Doubles Median Survival in Later Treatment
The Phase III CLARITY-Gastric01 trial tested Sone-Ve in patients with advanced or metastatic gastric cancer, gastroesophageal junction cancer and certain other cancers that express Claudin 18.2, or CLDN18.2.
Among patients who had received at least two previous treatments, median overall survival was 10 months with Sone-Ve. This compared with five months for those who received the physician’s choice of treatment.
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This represents a 53% reduction in the relative risk of death in this group.
In the wider group of patients receiving treatment in the second-line or later setting, median overall survival among those who had received at least two previous drug treatments was 10.6 months. This compared with 6.4 months in the control group.
AstraZeneca reported a 42% decrease in the relative risk of death in this population.
Overall survival measures how long patients remain alive after a specified starting point in a study.
Median survival is the point at which half of the patients in a group are alive and half have died. These figures represent outcomes for the study groups and do not predict how long an individual patient will live.
How Does Sone-Ve Work?
Sonesitatug vedotin belongs to a class of cancer medicines called antibody-drug conjugates (ADCs). These medicines combine an antibody that recognises a specific target with a potent drug payload designed to act against cancer cells.
Sone-Ve targets CLDN18.2, a protein found on the surface of some stomach and gastrointestinal cancer cells. By binding to this target, the medicine helps deliver its drug payload to cells that express the protein.
The trial involved patients whose tumours expressed CLDN18.2, with at least 25% of tumour cells showing the protein.
This is a broader threshold than the 75% expression required for an approved treatment targeting the same protein in a relevant setting.
If the findings support future regulatory approval and clinical use, the lower threshold could make targeted treatment available to a broader group of patients.
However, eligibility would depend on the eventual approved indication, required testing and medical assessment.
Trial Misses Key Progression-Free Survival Goal
The trial’s main outcome, progression-free survival, was not statistically significant compared with the assessment conducted through an independent review.
Progression-free survival measures how long patients live without their disease worsening or progressing.
Across the overall trial population, median progression-free survival was 4.2 months for patients receiving Sone-Ve. It was 3.8 months for patients receiving the comparison treatment.
The difference was not statistically significant in the trial’s initial analysis.
The results did not show an improvement in this measure, even though overall survival improved.
Investigators and regulators will need to consider the complete set of outcomes. These include the strength of the survival benefit, progression-free survival results, safety and trial design. This will help them assess the drug’s clinical relevance.
What Did the Trial Show About Safety?
The results showed that serious side effects were less common among patients in the Sone-Ve group than among those receiving the chemotherapy comparison treatment.
Serious adverse events occurred in 36.4% of patients treated with Sone-Ve, compared with 44.8% of patients in the comparison group.
However, stomach-related side effects were more common with Sone-Ve. These occurred in 11.1% of patients receiving the experimental drug, compared with 6.3% in the comparison group.
These findings do not mean that the experimental drug is free of serious risks.
Safety depends on the type and severity of side effects, the patient’s overall health and how the medicine is administered. A more detailed assessment will be needed to understand the treatment’s overall benefit-risk profile.
What Will Happen Next for AstraZeneca’s Experimental Drug?
The trial results are encouraging for AstraZeneca’s experimental drug. They provide further support for the clinical development of Sone-Ve for patients with advanced stomach and related gastrointestinal cancers.
However, the company will need to complete the regulatory review and approval process before the drug can be approved for a specific condition.
The trial results alone do not mean the drug has been approved or is routinely available to patients.
For people with advanced stomach cancer, the findings are encouraging because treatment options can become limited when the disease progresses after initial therapies.
However, Sone-Ve is not a proven cure, and the results do not guarantee that every patient will experience the same survival benefit.
The next steps will include further review of the clinical data, regulatory assessment and additional research to identify which patients are most likely to benefit from the treatment.
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