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Clinicians report success in the first trial of the drug in a patient with thrombotic thrombocytopenic purpura
Last reviewed: 02.07.2025
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A team of researchers from Massachusetts General Hospital used a new drug to save the life of a patient with immune thrombotic thrombocytopenic purpura (iTTP), a rare disorder characterized by the uncontrolled formation of blood clots in small blood vessels.
The team described the first clinical case of the drug being used to treat iTTP in the New England Journal of Medicine.
"The drug is a genetically modified version of the missing enzyme in iTTP, and we showed that it was able to reverse the progression of the disease in a patient with an extremely severe form of the condition," said lead author Pavan K. Bendapudi, MD, an investigator in the Division of Hematology and Transfusion Service at Massachusetts General Hospital and an associate professor of medicine at Harvard Medical School.
ITTP results from an autoimmune attack on the enzyme ADAMTS13, which is responsible for breaking down a large protein involved in blood clotting. The mainstay of therapy for this life-threatening blood disorder is plasmapheresis, which removes harmful autoantibodies and provides additional ADAMTS13.
Plasmapheresis induces a clinical response in most patients, but can restore at most only about half of the normal ADAMTS13 activity. In contrast, the recombinant form of human ADAMTS13 (rADAMTS13) offers the possibility of greatly increased delivery of ADAMTS13.
RADAMTS13 was recently approved for patients with congenital thrombotic thrombocytopenic purpura, which occurs in patients born with a complete loss of the ADAMTS13 gene.
It remains questionable whether rADAMTS13 might be effective in iTTP given the presence of inhibitory anti-ADAMTS13 autoantibodies, but Bendapudi and colleagues have received clearance from the US Food and Drug Administration to use rADAMTS13 provided by the manufacturer under a compassionate use protocol in a dying patient with treatment-resistant iTTP.
"We found that rADAMTS13 rapidly reversed the disease process in this patient, despite the existing belief that inhibitory autoantibodies against ADAMTS13 would render the drug useless in this condition," Bendapudi said.
"We were the first doctors to use rADAMTS13 to treat iTTP in the United States, and in this case it helped save the life of a young mother."
Bendapudi noted that rADAMTS13 infusion suppressed the patient's inhibitory autoantibodies and reversed the thrombotic effects of iTTP. This effect was observed almost immediately after rADAMTS13 administration, after daily plasma exchange had failed to induce remission.
"I believe rADAMTS13 has the potential to replace the current standard of care for acute iTTP. We will need larger, well-designed trials to evaluate this possibility," Bendapudi said.
A randomized phase IIb clinical trial of rADAMTS13 in iTTP has been initiated.