New Stomach Cancer Drug Doubles Survival Time in Clinical Trial

An experimental drug developed by AstraZeneca has shown promising results in patients with advanced stomach cancer who had already undergone at least two previous treatments. According to findings from a late-stage clinical trial presented on Sunday and reported by Reuters, patients receiving the treatment lived significantly longer than those given conventional chemotherapy.

The drug, known as sone-ve, is an antibody-drug conjugate, a treatment that combines an antibody designed to target cancer cells with a chemotherapy drug. In the study, patients who received sone-ve had a median overall survival of approximately 10 months, compared with five months for patients who received chemotherapy selected by their doctors. The results represented a 53% reduction in the risk of death during the study period.

"A five-month improvement in overall survival is very clinically meaningful in a patient population that is difficult to treat," said Susan Galbraith, AstraZeneca's executive vice president of oncology and hematology research and development.

The detailed findings, based on a study involving 532 patients, were presented at the European Society for Medical Oncology conference in Madrid. The presentation came a month after AstraZeneca agreed to invest $2 billion in biopharmaceutical company Summit Therapeutics and explore combining sone-ve with Summit's bispecific antibody drug, ivonescimab.

The AstraZeneca trial focused on patients with gastroesophageal cancer whose tumors expressed a protein called claudin 18.2, or CLDN18.2. This protein is found on the surface of certain cancer cells and can serve as a target for specialized treatments.

To qualify for the trial, at least 25% of a patient's tumor cells needed to express CLDN18.2. By comparison, an existing approved treatment targeting the same protein requires expression in at least 75% of tumor cells.

According to Galbraith, the lower threshold could potentially double the number of patients eligible for treatment. She also expressed optimism about the possibility of using the drug earlier in the course of cancer treatment, rather than reserving it for patients who have already received multiple therapies.

A separate study involving more than 2,000 patients is already investigating whether sone-ve could be effective when given earlier in the course of treatment.

Although the trial demonstrated a meaningful improvement in overall survival, not all of its findings were statistically significant. Progression-free survival, which measures how long patients live without their cancer worsening, was one of the study's main endpoints. Patients receiving sone-ve had a median progression-free survival of 4.2 months, compared with 3.8 months among those receiving conventional chemotherapy. However, this difference did not reach statistical significance.

Galbraith explained that measuring disease progression can be particularly challenging in stomach cancer because tumors often spread in a diffuse pattern, making changes more difficult to assess accurately.

Despite this limitation, the improvement in overall survival represents an encouraging development for patients with advanced gastroesophageal cancer who have limited treatment options remaining. Further research will help determine whether sone-ve can offer similar benefits to a broader group of patients and whether introducing the drug earlier in treatment could improve outcomes. For now, the findings offer hope for a difficult-to-treat form of cancer, although the treatment remains experimental.