Grail Cancer Blood Test Fails Key NHS Trial, Shares Plummet

Grail, Inc. Shares plummeted 47% in after-hours trading Thursday following the announcement that a large-scale study of its cancer detection test, Galleri, failed to meet its primary goal in a trial conducted with the National Health Service (NHS) in England, the company said.

The Galleri test analyzes blood samples for DNA fragments shed by cancerous tumors, aiming to identify cancer before symptoms appear. Grail has marketed the test as capable of detecting over 50 different types of cancer, positioning it as a potential breakthrough in early cancer screening. Despite not yet receiving approval from the U.S. Food and Drug Administration, the company sold 185,000 tests in 2025, generating $136.8 million in revenue, according to a company statement.

The NHS study’s specific findings have not been publicly released, as detailed reporting is behind a paywall, but the failure to achieve its primary objective casts doubt on the test’s effectiveness as a widespread cancer screening tool. The initial promise of Galleri included the ability to pinpoint the potential location of the tumor, guiding further diagnostic investigations.

Grail, founded in 2015 and based in Menlo Park, California, was acquired by Illumina in 2021. However, regulatory concerns led to an order from the European Union requiring Grail to be spun out from Illumina, a process completed on June 24, 2024.

Angus Chen, a journalist at STAT News focusing on cancer, has reported extensively on the development of cancer detection technologies. He has received multiple national journalism awards, including two Edward R. Murrow awards and the Biedler Prize for Cancer Journalism.