The U.S. Food and Drug Administration (FDA) on Friday said it has received postmarketing reports of neutralizing antibodies to ADAMTS13 in patients treated with Adzynma (recombinant ADAMTS13), including one pediatric death.
Takeda Pharmaceutical Co., Ltd. (NYSE:TAK) Adzynma is approved as a prophylactic or on-demand enzyme replacement therapy for congenital thrombotic thrombocytopenic purpura (cTTP) and contains two rADAMTS13 variants—one native and one with a single amino-acid modification.
A genetic mutation causes cTTP, which is a rare disorder.
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For reference, ADAMTS13 is a key regulator of blood clotting, preventing excessive clot formation in normal circulation.
Its primary function is to cleave vWF, a large protein that helps platelets clump together to form clots.
By cutting large vWF into smaller pieces, ADAMTS13 prevents platelets from clumping together unnecessarily, which helps avoid abnormal blood clots.
The reported fatality involved a child with a history of severe allergic reactions to fresh frozen plasma.
The patient developed neurologic symptoms and was found to have neutralizing antibodies about 10 months after initiating prophylactic Adzynma.
Current assays cannot distinguish antibodies targeting the recombinant enzyme from those against endogenous ADAMTS13.
Adzynma's U.S. label already flags the potential for neutralizing antibody development under "Immunogenicity," and the Patient Package Insert advises monitoring for inhibitors.
No neutralizing antibodies were reported during clinical trials, and the label does not yet reflect the postmarketing cases tied to serious or fatal outcomes.
Price Action: TAK stock is up 1.88% at $14.33 at the last check on Friday.
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