Grail's NHS-Galleri Cancer Screening Trial Misses Primary Endpoint
Grail's NHS-Galleri trial of 142,000 participants failed to achieve statistically significant reduction in late-stage cancer diagnoses, though secondary endpoints showed four-fold improvement in overall cancer detection rate. Stock fell 48% following the announcement.
Grail announced February 19 that its landmark NHS-Galleri trial of 142,000 participants did not achieve its primary endpoint of statistically significant reduction in stage III-IV cancer diagnoses. The announcement triggered a 48% decline in Grail's stock price, marking a significant setback for the company's regulatory pathway and commercial prospects.
The randomized, controlled NHS-Galleri trial evaluated annual multi-cancer screening with the Galleri test over three years in 142,000 demographically representative participants aged 50 to 77 in England's National Health Service. Participants provided three blood samples over two years, approximately 12 months apart. The primary objective was to demonstrate a reduction in late-stage (III-IV) cancers in people who received the Galleri test compared with those who did not, measured across three clinically important groups of cancers, with initial focus on a pre-specified group of 12 cancer types that together represent approximately two-thirds of cancer deaths in England and the United States. These cancer types include anus, bladder, colorectal, esophagus, head and neck, liver/bile duct, lung, lymphoma, myeloma, ovary, pancreas, and stomach.
Despite missing the primary endpoint, the trial demonstrated substantial progress in secondary metrics. Screening with the Galleri test resulted in a four-fold improvement in the overall cancer detection rate when added to standard of care screening for breast, colorectal, cervical, and high-risk lung cancers. The trial showed a substantial increase in the absolute number of Stage I-II cancers detected in the 12 pre-specified deadly cancer types that are typically found in late stages. Additionally, screening with the Galleri test resulted in a substantial reduction in the number of cancers detected clinically through emergency presentation, which are associated with significantly higher mortality and healthcare costs.
The Galleri test's performance metrics—positive predictive value (PPV), specificity, and Cancer Signal of Origin (CSO) accuracy—remained consistent with the range previously reported from Grail's North American studies. The Galleri test demonstrated the ability to detect more than 50 types of cancer before symptoms appear through a simple blood draw. No serious safety concerns were reported in participants who received the Galleri test during the NHS-Galleri trial.
Grail noted that there was a higher than anticipated incidence of Stage III cancers in the trial, and that the time to diagnostic resolution appears to improve over time as physicians gain experience with the Galleri test and diagnostic workup. The company plans to extend the trial's follow-up period by 6-12 months, suggesting the potential for a stronger effect with longer follow-up as data matures.
Despite the trial disappointment, Grail reported strong commercial momentum, with 185,000 Galleri tests sold in 2025. The company completed its FDA premarket approval (PMA) submission in January 2026, with the FDA application including metrics focused on test performance, clinical validation, and clinical benefit of detection at Stages I through III, including reduction in Stage IV cancer diagnoses. The company was expanding its field-based sales and medical teams to support growing demand.