The legal action, spearheaded by The Gross Law Firm, centers on allegations that GRAIL executives misled shareholders regarding the status of the NHS-Galleri trial. According to the complaint, the company issued positive statements while allegedly concealing material facts about the trial's ability to demonstrate a reduction in Stage III-IV cancers. The firm contends that GRAIL failed to provide transparent data, potentially obscuring known trends that indicated the study duration was insufficient to reach its primary endpoint.

On February 19, 2026, GRAIL confirmed that the study failed to meet its primary goal of a statistically significant reduction in advanced-stage cancers, citing a need for longer follow-up times. The market reaction was swift: the stock price plummeted from $101.53 on February 19 to $50.21 on February 20. Shareholders who purchased during the specified window are eligible to participate in the litigation at no direct cost, with the August deadline serving as the final opportunity for those wishing to be appointed as lead plaintiff.