Grail disclosed that its large NHS-Galleri multicancer early detection (MCED) trial failed to meet the study’s primary endpoint, triggering a sharp sell-off in the company’s shares. The trial, run in England’s National Health Service and enrolling roughly 142,000 participants, did not show a statistically significant reduction in late-stage (III–IV) cancer diagnoses versus standard care. Grail highlighted favorable trends in a pre-specified subset of 12 deadly cancers and plans to extend follow-up to assess whether effects strengthen as data mature. The topline miss immediately pressured Grail’s market value, with investors reacting to implications for regulatory review and reimbursement momentum. Grail executives have told regulators they expect the U.S. FDA and payers to review the totality of evidence; the company also reiterated ongoing commercialization efforts. Independent experts cautioned that screening trials are complex and that trial design and population selection influence outcomes; commentary from biostatisticians and clinicians was cited in media coverage.