AstraZeneca's stomach cancer drug extends overall survival, late-stage trial data finds

By Bhanvi Satija

MADRID, Oct 25 (Reuters) - AstraZeneca's AZN.L experimental drug sone-ve helped patients with advanced stomach cancer who had received at least two prior treatments to live longer than analysts had expected, according to late-stage trial data presented on Sunday.

Patients on the drug lived a median of 10 months, compared with 5 months on their doctor's choice of chemotherapy, a 53% reduction in the risk of death.

"A 5-month improvement in overall survival is very clinically significant in a difficult to treat patient population," said Susan Galbraith, executive vice president of oncology haematology research and development at AstraZeneca.

A win on overall survival could boost confidence in the drug's commercial potential, as it did not reach statistical significance on its other goal of progression-free survival in the study. AstraZeneca has said it expects the drug could bring in between $3 billion and $5 billion in peak sales, but analysts' estimates are closer to $1 billion.

The drug, sonesitatug vedotin, or sone-ve, belongs to a class of treatments called antibody drug conjugates, or ADCs, often described as guided missiles as they deliver therapy to cancer cells while sparing healthy cells.

"It's another data set that reinforces our vision that we've had for a long time, that ADCs can replace and improve on backbone chemotherapy in many different tumour types," Galbraith said.

Analysts were expecting an overall survival hazard ratio, or risk of death, of about 0.7 or lower, with a gain of at least 2 months.

ASTRAZENECA INVESTS IN AND WORKS WITH SUMMIT THERAPEUTICS

The detailed data from the 532-patient study was presented at the conference of the European Society for Medical Oncology in Madrid on Sunday, a month after AstraZeneca agreed to invest $2 billion in the biopharmaceutical company Summit Therapeutics and to test sone-ve alongside Summit's bispecific antibody ivonescimab.

Patients with gastroesophageal cancer in AstraZeneca's study were enrolled if at least 25% of their tumour cells showed claudin 18.2, a protein found on many cancer cells. The approved treatment for this target requires a 75% cutoff.

Galbraith said the lower threshold could double the number of patients who would be able to receive treatment.

"I think that bodes well for the opportunity to move it into the earlier line setting," she said. Another study of more than 2,000 patients is already testing the drug earlier in a patient's course of therapy.

HSBC analysts said the miss makes it harder to compare the drug with IBI343, a rival claudin 18.2 therapy being developed by Takeda 4502.T and Innovent 1801.HK, which succeeded on its progression-free survival goal in a late-stage study.

Serious side effects were less common with AstraZeneca's drug, 36.4% versus 44.8% on chemotherapy, though stomach-related side effects were more frequent, at 11.1% versus 6.3%.