FDA

FDA investigating death linked to neutralizing antibodies after Adzynma treatment

November 24, 2025

Since the drug's approval, FDA has received postmarketing reports of neutralizing antibodies to ADAMTS13, including one death, in congenital thrombotic thrombocytopenic purpura (cTTP) patients treated with Adzynma (ADAMTS13, recombinant-krhn). Adzynma is indicated for prophylactic or on-demand enzyme replacement therapy in adult and pediatric patients with cTTP and contains two versions of recombinant ADAMTS13: native sequence and a variant (rADAMTS13.R97) that differs by a single amino acid.

The reported death occurred in a pediatric cTTP patient who developed neutralizing antibodies about 10 months after starting prophylactic Adzynma. The patient had prior severe allergic reactions to fresh frozen plasma and presented with neurologic symptoms that progressed. It's important to note that current assays are unable to distinguish neutralizing antibodies to recombinant ADAMTS13 from neutralizing antibodies to endogenous ADAMTS13. FDA is investigating the risk of neutralizing antibodies with serious, including fatal, outcomes and evaluating the need for further regulatory action.

Source:

(2025, November 24). FDA. FDA Investigating Death Due to Neutralizing Antibodies to ADAMTS13 following Adzynma Treatment of Congenital Thrombotic Thrombocytopenic Purpura. https://www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/fda-investigating-death-due-neutralizing-antibodies-adamts13-following-adzynma-treatment-congenital