The FDA announced an investigation into Takeda’s Adzynma (approved 2023 for congenital thrombotic thrombocytopenic purpura) after reports that patients developed neutralizing antibodies and a pediatric death that appears related to treatment. The agency said available assays cannot yet distinguish antibodies against the lab‑manufactured enzyme from those targeting the native protein. Takeda reported no confirmed causal link but acknowledged the company is conducting an internal assessment; the FDA issued a safety communication and is evaluating further regulatory action. Adzynma generated modest sales—about 4.8 billion yen in the first half of the fiscal year—but safety concerns could prompt label or usage changes. Regulators and clinicians will watch assay development and post‑market surveillance closely to determine whether neutralizing antibodies represent a broader safety signal requiring changes in prescribing or monitoring.