Rezolute announced its Phase III Sunrize trial of ersodetug failed to meet primary and key secondary endpoints in congenital hyperinsulinism, triggering an immediate market reaction and an 80–90% collapse in share price. The data showed non‑significant differences versus placebo on weekly hypoglycemia event reductions and time‑in‑hypoglycemia, and the study included two serious hypersensitivity events leading to discontinuations. Company management said it will meet the FDA to determine next steps and will analyze potential subgroup signals and ongoing tumor HI studies. Investors and partners reacted swiftly, repricing the company and prompting questions about the robustness of earlier signals and trial design choices. The result highlights the risk of late‑stage failures in rare‑disease monoclonal antibody programs and the importance of placebo dynamics in small cohorts. Rezolute’s path forward depends on regulator discussions and whether any mechanistic insights or alternative indications can salvage value from the platform.