India Pharma Outlook Team | Monday, 26 October 2026
AstraZeneca’s latest trial result for its experimental stomach cancer drug sonesitatug vedotin (Son-ve) is putting CLDN18.2 testing in the spotlight as a key part of precision oncology.
Data from the Phase III CLARITY-Gastric01 trial showed that the treatment reduced the risk of death by 53 percent among patients receiving third-line or later treatment, doubling median overall survival to 10 months from five months with physician-selected chemotherapy.
Presented at the European Society for Medical Oncology Congress, the findings also highlighted a 25 percent tumour-expression threshold, raising questions about how biomarker criteria could influence treatment eligibility in advanced gastric cancer.
The CLDN18.2 biomarker is a protein found on the surface of certain cancer cells and has become a target for therapies designed to identify and attack tumours expressing it.
In the CLARITY-Gastric01 trial, patients were eligible if at least 25 percent of their tumour cells showed CLDN18.2 expression at any staining intensity.
This differs from the 75 percent expression threshold used to define eligibility for an existing CLDN18.2-targeted treatment, zolbetuximab, in its approved gastric cancer indication.
CLDN18.2 testing could help identify patients whose tumours express the target at lower levels, potentially expanding the population eligible for emerging targeted therapies.
AstraZeneca reported that the survival benefit was consistent across the trial’s predefined biomarker-expression subgroups, including patients with expression between 25 percent and 75 percent.
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The AstraZeneca Sone-Ve clinical trial results also draw attention to the potential role of antibody-drug conjugates in advanced cancer care.
The therapy combines an antibody that recognizes a target on cancer cells with a drug payload designed to kill them.
In the broader trial population receiving second-line or later treatment, Sone-Ve reduced the risk of death by 42 percent, with median overall survival reaching 10.6 months compared with 6.4 months for the comparator group.
However, the independently assessed progression-free survival endpoint did not reach statistical significance, an important limitation when interpreting the findings.
Grade 3 or higher treatment-related adverse events occurred in 36.4 percent of patients receiving Sone-Ve, compared with 44.8 percent in the comparator group.
The CLDN18.2 expression threshold for targeted treatment could become increasingly relevant as pharmaceutical companies investigate therapies for wider patient populations.
AstraZeneca is also evaluating Sone-Ve in a Phase III first-line treatment program, including combinations with other medicines.
The findings could increase interest in CLDN18.2 testing as a tool for guiding gastric cancer treatment, although further clinical evidence will be needed to establish how broadly the approach can be applied.
Until further evidence and regulatory decisions emerge, the 25 percent threshold represents a trial eligibility criterion rather than an established change in treatment guidelines.
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