AstraZeneca Sone-Ve Stomach Cancer Trial: Survival Results (2026)

OneDayMD Editorial Team | Last updated October 26, 2026

AstraZeneca's experimental stomach cancer drug, sonesitatug vedotin (Sone-Ve), has doubled median overall survival in a late-stage clinical trial involving patients with advanced, biomarker-positive gastroesophageal cancer who had already received multiple treatments.

In the Phase III CLARITY-Gastric01 trial, patients receiving Sone-Ve in the third-line or later treatment setting had a median overall survival of 10 months, compared with 5 months among patients receiving their physician's choice of treatment. The result represents a substantial survival signal in a difficult-to-treat population.

However, the findings need context. Although Sone-Ve met its overall survival primary endpoint in the third-line-and-later population, it did not meet the trial's other primary endpoint for progression-free survival in the broader second-line-and-later population. The drug is investigational, and the results do not yet establish it as a routine treatment option.

This article explains what the trial found, how Sone-Ve works, why the CLDN18.2 biomarker matters, what is known about its side effects, and what patients and clinicians should watch for next.

Key takeaways

• Median overall survival: 10.0 months with Sone-Ve versus 5.0 months with physician's-choice therapy in patients receiving third-line or later treatment.
• Relative mortality hazard: 53% lower in that treatment subgroup, based on a hazard ratio of 0.47.
• Broader trial population: Median overall survival was 10.6 versus 6.4 months in the second-line-and-later population.
• Important limitation: The primary progression-free survival endpoint was not met at the prespecified statistical threshold.
• Biomarker: Trial eligibility included tumours with CLDN18.2 expression in at least 25% of tumour cells at any staining intensity.
• Current status: Sone-Ve remains investigational; trial results alone do not constitute regulatory approval.

What Is AstraZeneca's Sone-Ve Stomach Cancer Drug?

Sonesitatug vedotin, also known as Sone-Ve or AZD0901, is an investigational antibody-drug conjugate (ADC) being developed by AstraZeneca for cancers expressing a protein called claudin 18.2, commonly abbreviated as CLDN18.2.

An antibody-drug conjugate combines a targeting antibody with a cancer-killing drug payload. The antibody is designed to bind a particular target on cancer cells, while the attached drug delivers a cytotoxic effect after the conjugate enters the cell and releases its payload.

Sone-Ve consists of an anti-CLDN18.2 monoclonal antibody, a cleavable linker and monomethyl auristatin E (MMAE), a cytotoxic compound that disrupts microtubules and interferes with cell division.

The therapeutic rationale is to direct the payload towards tumour cells expressing CLDN18.2. This approach does not guarantee that only cancer cells will be affected, and antibody-drug conjugates can still cause significant adverse effects.

CLDN18.2 is particularly relevant to gastric and gastroesophageal cancers because the protein can become accessible on cancer cells as the normal architecture of the stomach lining is disrupted. Its expression varies among tumours, making biomarker testing important when evaluating CLDN18.2-targeted treatments.

Source: AstraZeneca's CLARITY-Gastric01 results announcement.

CLARITY-Gastric01: What Did the Phase III Trial Find?

CLARITY-Gastric01 was a global Phase III clinical trial comparing Sone-Ve with investigator-selected treatment in patients with previously treated, advanced or metastatic CLDN18.2-positive gastroesophageal cancer.

The reported efficacy population included 532 patients in the overall second-line-and-later analysis, comprising 267 patients assigned to Sone-Ve and 265 assigned to investigator's-choice therapy. The subgroup receiving third-line or later treatment comprised 178 patients in the Sone-Ve arm and 177 in the comparator arm.

Patients had locally advanced or metastatic disease. The company's trial announcement described gastric cancer, gastroesophageal junction cancer and oesophageal adenocarcinoma, with CLDN18.2 expression in at least 25% of tumour cells at any staining intensity.

The trial had two primary endpoints: overall survival in the third-line-and-later subgroup and progression-free survival in the overall second-line-and-later population. Overall survival in the broader population was a key secondary endpoint.

1. Overall Survival in Third-Line or Later Treatment

Measure	Sone-Ve	Investigator's choice
Patients analysed	178	177
Median overall survival	10.0 months	5.0 months
Hazard ratio for death	0.47 (95% confidence interval 0.36–0.62)
Reported p-value	p < 0.000001
Alive at 12 months	38.1%	18.1%

The primary overall survival endpoint was met. Median overall survival was twice as long in the Sone-Ve group as in the comparator group: 10 months versus 5 months.

The hazard ratio of 0.47 indicates a 53% lower relative hazard of death during the analysed follow-up period. This is not the same as saying that every patient has a 53% lower individual probability of dying, nor does it mean that every patient will live five months longer.

Median overall survival is a group-level measure: it is the point at which half the patients in the relevant group have experienced the event being measured. Individual outcomes can differ substantially.

2. Overall Survival in the Broader Population

Measure	Sone-Ve	Investigator's choice
Patients analysed	267	265
Median overall survival	10.6 months	6.4 months
Hazard ratio for death	0.58 (95% confidence interval 0.47–0.73)
Reported p-value	p < 0.000004
Alive at 12 months	42.6%	27.8%

In the broader second-line-and-later population, median overall survival was 10.6 months with Sone-Ve and 6.4 months with investigator's-choice therapy. The hazard ratio of 0.58 corresponds to a 42% lower relative hazard of death during follow-up.

This is important because the survival signal was not limited to the later-line subgroup. Nevertheless, the trial's primary overall survival endpoint was specifically defined in the third-line-and-later population; the broader population's overall survival result was a key secondary endpoint.

3. Progression-Free Survival: The Important Qualification

Progression-free survival (PFS) measures the time patients live without their cancer progressing or death occurring, according to the trial's specified definition.

Measure	Sone-Ve	Investigator's choice
Median progression-free survival	4.2 months	3.8 months
Hazard ratio	0.77 (95% confidence interval 0.62–0.96)
Reported p-value	p = 0.053193
Primary endpoint status	Not met at the prespecified statistical threshold

The reported median difference was only 0.4 months when progression-free survival was assessed by blinded independent central review. AstraZeneca reported a p-value of 0.053193 and stated that the primary PFS endpoint was not met.

The published summary gives a hazard-ratio confidence interval that excludes 1 alongside a p-value above 0.05. These statistics do not ordinarily align under a simple, unadjusted two-sided test. The summary does not provide enough methodological detail to fully reconcile that difference, so readers should consult the complete conference presentation and statistical analysis when available.

The overall interpretation is therefore nuanced: Sone-Ve demonstrated a statistically significant overall survival benefit, but the trial did not satisfy its prespecified primary progression-free survival success criterion. The two findings should be reported together rather than treating the survival result as proof that every measure of cancer control improved significantly.

Sources: AstraZeneca and Reuters, October 25, 2026.

Why the CLDN18.2 Biomarker Matters

One of the potentially important aspects of CLARITY-Gastric01 is its approach to defining CLDN18.2 positivity.

For the trial, eligible tumours expressed CLDN18.2 on at least 25% of tumour cells at any staining intensity. The results included patients whose tumours had lower CLDN18.2 expression as well as those with higher expression.

AstraZeneca has suggested that this broader threshold could expand the population potentially eligible for a CLDN18.2-targeted treatment. That is a development hypothesis, not a guarantee that all patients meeting the trial's threshold will benefit or that regulators will approve the drug using the same criteria.

How Does This Compare With Approved CLDN18.2 Treatment?

In the United States, the FDA approved zolbetuximab-clzb (Vyloy) with fluoropyrimidine- and platinum-containing chemotherapy on October 18, 2024, for first-line treatment of adults with locally advanced unresectable or metastatic HER2-negative gastric or gastroesophageal junction adenocarcinoma whose tumours are CLDN18.2-positive according to an FDA-approved test.

Zolbetuximab and Sone-Ve are different treatments. Zolbetuximab is a CLDN18.2-directed antibody, whereas Sone-Ve is an antibody-drug conjugate that carries a cytotoxic payload.

Their clinical evidence also comes from different treatment settings. CLARITY-Gastric01 studied Sone-Ve after prior treatment, while the established US indication for zolbetuximab is in the first-line setting with chemotherapy in an appropriately selected population.

The CLARITY-Gastric01 results do not establish that Sone-Ve is superior to zolbetuximab. The two drugs have not been compared head-to-head in this trial, and the results should not be interpreted as a direct comparison between them.

For regulatory details, consult the FDA's zolbetuximab approval announcement.

Sone-Ve Side Effects: What Is Known So Far?

Antibody-drug conjugates are designed to direct a drug payload towards cells carrying a target, but their toxicity profile can still affect the gastrointestinal tract, blood counts and other tissues.

In the reported CLARITY-Gastric01 results, the most frequently reported adverse events with Sone-Ve included nausea, decreased appetite and vomiting.

Reported adverse event	Sone-Ve	Investigator's choice
Nausea, any reported grade	54.4%	26.6%
Decreased appetite, any reported grade	43.3%	24.2%
Vomiting, any reported grade	41.0%	24.6%
Grade 3 or higher treatment-related adverse events	36.4%	44.8%
Grade 3 or higher neutropenia	10.3%	25.4%

Grade 3 or higher adverse events are generally severe or medically significant, although the clinical meaning depends on the specific event. Fewer grade 3 or higher treatment-related adverse events were reported in the Sone-Ve arm, but gastrointestinal adverse effects occurred more often than with the comparator treatment.

These figures do not establish that Sone-Ve is universally safer than chemotherapy. Different treatments produce different types of toxicity, and an individual patient's medical history, blood counts, nutritional status and other medicines can influence the balance of benefit and risk.

Supportive care, symptom monitoring and timely communication with the oncology team remain essential during cancer treatment. The full safety profile also requires continued assessment as more patients receive the drug in clinical studies.

Source: OncLive's CLARITY-Gastric01 trial coverage.

Could Sone-Ve Become a New Stomach Cancer Blockbuster?

AstraZeneca has projected potential peak annual sales of $3 billion to $5 billion for Sone-Ve, while Reuters reported that analysts' estimates were closer to $1 billion.

The commercial opportunity depends on several factors beyond the headline survival result:

• Regulatory approval: The drug must obtain approval for a defined indication before routine commercial use in that jurisdiction.
• Eligible patient population: Biomarker prevalence, the approved CLDN18.2 testing threshold and treatment-line restrictions will affect the number of patients who qualify.
• Comparative clinical evidence: Clinicians will consider overall survival, progression-free survival, response rates, quality of life, tolerability and available alternatives.
• Competition: Other CLDN18.2-targeted treatments and established chemotherapy-based regimens may compete for different or overlapping patient populations.
• Access and reimbursement: Pricing, diagnostic availability, insurance coverage and local regulatory decisions will influence uptake.

A blockbuster forecast is a commercial projection, not proof of clinical value or future sales. Similarly, a strong Phase III survival result does not guarantee approval, widespread adoption or success in earlier treatment settings.

Source: Reuters' October 25, 2026 report.

What Happens Next for Sone-Ve?

The next major question is whether Sone-Ve can demonstrate an acceptable benefit-risk profile earlier in the treatment pathway.

AstraZeneca has reported that another Phase III programme, CLARITY-Gastric02, is investigating Sone-Ve with capecitabine, with or without the investigational immunotherapy rilvegostomig, as first-line treatment for advanced or metastatic gastric cancer, gastroesophageal junction cancer and oesophageal adenocarcinoma.

Further development will need to clarify whether the drug improves outcomes in earlier treatment settings, how its benefit compares with contemporary standard-of-care regimens, and which biomarker-defined groups derive the greatest benefit.

Important evidence questions include:

• Can the overall survival benefit be confirmed with mature follow-up and additional analyses?
• How should the reported PFS endpoint result be interpreted alongside the overall survival findings?
• Will subsequent studies confirm benefit in patients with lower CLDN18.2 expression?
• How will quality of life, treatment discontinuation and longer-term safety compare with available alternatives?
• Which patients benefit most, based on tumour biology, previous treatment and other clinical characteristics?

As of October 26, 2026, Sone-Ve remains an investigational medicine. The CLARITY-Gastric01 results are important clinical trial findings, but they should not be confused with regulatory approval or a recommendation to replace established treatment.

Trial record: ClinicalTrials.gov — CLARITY-Gastric01 (NCT06346392).

What the Results Mean for Patients and Families

For people living with advanced stomach or gastroesophageal cancer, a treatment that improves overall survival after earlier treatments have failed can be meaningful. The CLARITY-Gastric01 results provide evidence that targeting CLDN18.2 with an antibody-drug conjugate may offer a further treatment strategy for selected patients.

However, the study does not show that every patient with stomach cancer will benefit. The results apply to a defined population with advanced disease, prior treatment and the required biomarker expression. They should not be extrapolated automatically to early-stage stomach cancer, CLDN18.2-negative tumours, other cancer types or people who have not received prior treatment.

Patients can ask their oncology team whether CLDN18.2 testing is relevant to their diagnosis, whether the results would affect treatment selection, and whether a clinical trial is appropriate. They should also discuss other established biomarkers and treatment options relevant to their tumour, including HER2, mismatch-repair or microsatellite instability status, and PD-L1 where clinically indicated.

Biomarker testing should be interpreted in the context of the complete pathology report and clinical situation. A positive result alone does not determine which medicine is best or whether a particular treatment is approved for that patient.

Do not delay or discontinue prescribed cancer treatment because of an investigational drug announcement. Treatment decisions should be made with the treating oncology team after considering the patient's diagnosis, previous treatment, goals of care, risks and available options.

Frequently Asked Questions

1. What is AstraZeneca's new stomach cancer drug?

Sonesitatug vedotin, also called Sone-Ve or AZD0901, is an investigational antibody-drug conjugate targeting CLDN18.2, a protein expressed on certain gastric and gastroesophageal cancer cells. It combines a targeting antibody with a cytotoxic payload designed to damage cancer cells.

2. Did Sone-Ve really double survival in a Phase III trial?

Yes, median overall survival doubled from 5.0 to 10.0 months in the third-line-and-later subgroup of CLARITY-Gastric01. In the broader second-line-and-later population, median overall survival was 10.6 months versus 6.4 months. These are group-level trial results, not predictions of the survival time of an individual patient.

3. What does a 53% reduction in the risk of death mean?

The reported hazard ratio of 0.47 corresponds to a 53% lower relative hazard of death during the study follow-up compared with the investigator's-choice treatment group. It does not mean that every patient gains five months of life or that the individual probability of death falls by exactly 53%.

4. Did Sone-Ve meet all the primary endpoints?

No. Sone-Ve met the overall survival primary endpoint in the third-line-and-later population, but the trial did not meet its primary progression-free survival endpoint in the broader second-line-and-later population at the prespecified statistical threshold. Both findings are important when evaluating the study.

5. Is Sone-Ve approved for stomach cancer?

As of October 26, 2026, Sone-Ve is investigational. The Phase III findings do not themselves constitute regulatory approval, and the drug should not be regarded as a routinely available approved treatment on the basis of these results alone.

6. What is CLDN18.2, and why is testing important?

CLDN18.2 is a protein that can be accessible on certain gastric and gastroesophageal cancer cells. Sone-Ve is designed to target this protein. CLARITY-Gastric01 included tumours expressing CLDN18.2 on at least 25% of tumour cells at any staining intensity. Testing methods, thresholds and approved indications differ among treatments, so results should be interpreted by the oncology team.

7. Is Sone-Ve better than zolbetuximab (Vyloy)?

The CLARITY-Gastric01 trial did not compare Sone-Ve directly with zolbetuximab. Zolbetuximab is an approved first-line option for a defined group of CLDN18.2-positive, HER2-negative gastric or gastroesophageal junction adenocarcinomas in the United States, used with specified chemotherapy. The treatments have different mechanisms and evidence bases, and the results cannot establish which is superior.

8. What side effects were reported with Sone-Ve?

Nausea, decreased appetite and vomiting were among the most frequently reported adverse events. Grade 3 or higher treatment-related adverse events occurred in 36.4% of patients receiving Sone-Ve versus 44.8% receiving investigator's-choice therapy. The gastrointestinal side-effect profile and the drug's longer-term safety require continued evaluation.

Sources and Further Reading

1. AstraZeneca: CLARITY-Gastric01 Phase III results for sonesitatug vedotin, October 25, 2026. Primary source for the reported efficacy data and trial endpoints.
2. Reuters: AstraZeneca's stomach cancer drug extends overall survival, late-stage trial data finds, October 25, 2026. Independent reporting on clinical interpretation and commercial expectations.
3. ClinicalTrials.gov: CLARITY-Gastric01 (NCT06346392). Trial registration and study information.
4. US Food and Drug Administration: Approval of zolbetuximab with chemotherapy for gastric or gastroesophageal junction adenocarcinoma. Regulatory context for an existing CLDN18.2-targeted treatment.
5. OncLive: CLARITY-Gastric01 shows overall survival benefit in pretreated CLDN18.2-positive gastroesophageal carcinoma. Conference coverage and additional adverse-event details.

Editorial Disclaimer

This article is for educational and informational purposes only. It is not medical advice, a diagnosis or a recommendation to start, stop or change treatment. Investigational treatments may not be available outside clinical trials and are not necessarily approved in every country. Patients should discuss treatment decisions with a qualified oncology professional who understands their diagnosis and medical history.

OneDayMD aims to explain emerging medical research in context, distinguishing promising clinical findings from established treatment options. We report both clinically meaningful benefits and important evidence limitations.