The U.S. Food and Drug Administration opened an investigation into Takeda’s engineered enzyme therapy Adzynma following reports that patients developed neutralizing antibodies and after a pediatric patient death that appears related to treatment. Adzynma, approved in 2023 for congenital thrombotic thrombocytopenic purpura, replaces a deficient clot‑clearing enzyme; the FDA said current assays can’t distinguish antibodies to the therapeutic enzyme from those against the native protein. Takeda said it has seen no confirmed causal link and that the product’s overall benefit–risk profile remains intact, while regulators evaluate adverse event reports and lab testing limitations. The probe could lead to label changes, risk‑management measures, or new post‑market study requirements depending on findings; clinicians who prescribe Adzynma will need clear guidance on antibody monitoring and patient selection.