Thrombotic Thrombocytopenic Purpura (TTP) is a rare disorder caused by an enzyme deficiency. It can be hereditary or can be an acquired autoimmune condition. Due to the associated hyperactivity of a certain protein, blood clots form, enriched with blood platelets, and block the tiny blood vessels. The disorder is life-threatening and very difficult to treat, particularly in the acute phase. Researchers at MedUni Vienna's Division of Hematology and Hemastasology and Department of Clinical Pharmacology have developed a treatment strategy to prevent this clotting in the blood vessels.
In its acute phase, TTP is life-threatening. Blocking of blood vessels by blood clots, which aggregate on the overactive von Willebrand protein results in dangerous secondary diseases such as kidney failure, strokes or heart attacks, which can prove fatal.
"If patients survive this acute phase, which has to be treated by plasma exchange, then the autoimmune disease can easily be treated by immunosuppression. Even to the point that it can completely disappear," explains Paul Knöbl of MedUni Vienna's Division of Hematology and Hemastasology. However, approximately 10 – 20% of patients do not survive the acute phase of this disease. Every year, up to ten patients with TTP are treated at MedUni Vienna or in Vienna General Hospital. Viennese doctors and scientists are regarded as world leaders in the clinical testing of new treatments for this disease and, since 2009, they have published several clinical studies on the therapeutic inhibition of von Willebrand factor in patients with TTP.
In a study recently published in the prestigious "New England Journal of Medicine" – as the one in 2016 – the MedUni Vienna researchers have now demonstrated that the antibody caplazicumab prevents overactivity of the von Willebrand protein and is therefore able to halt the life-threatening clotting of blood platelets more quickly. This would make even the acute phase of the disease easier to treat. The biotech product caplacizumab is like an antibody and specifically inhibits the interaction of platelets with the von Willebrand factor. The drug is administered as a subcutaneous injection – a bit like an injection for preventing or treating thrombosis – and, as a result of the study conducted at MedUni Vienna, it has now been licensed and is available under the name Cablivi(R).
"In future this drug might also be used to treat similar diseases partially caused by overactivity of the von Willebrand factor and is therefore a new treatment option," says Bernd Jilma of MedUni Vienna's Department of Clinical Pharmacology. Another drug for treating hereditary TTP is currently being tested.
Service: New England Journal of Medicine
„Caplacizumab Treatment for Acquired Thrombotic Thrombocytopenic Purpura.“
Marie Scully, Spero R. Cataland, Flora Peyvandi, Paul Coppo, Paul Knöbl, Johanna A. Kremer Hovinga, Ara Metjian, Javier de la Rubia, Katerina Pavenski, Filip Callewaert, Debjit Biswas, Hilde De Winter, and Robert K. Zeldin, for the HERCULES Investigators. NEJM.org, Jan 9th 2019. DOI: 10.1056/NEJMoa1806311.