Caplacizumab approved for acquired Thrombotic Thrombocytopenic Purpura

A novel nanobody therapy caplacizumab (Cablivi) has been approved by the TGA as a treatment for acquired Thrombotic Thrombocytopenic Purpura (aTTP).

The humanised nanobody therapy is approved in Australia to treat adults experiencing an episode of aTTP in conjunction with plasma exchange and immunosuppression.

According to manufacturer Sanofi, caplacizumab binds to the protein von Willebrand Factor (vWF) suppressing its ability to adhere to platelets within 24 hours of a patient’s first treatment. This allows it to have an immediate effect on platelet adhesion, which inhibits the formation and accumulation of micro-clots that cause severe thrombocytopenia, microangiopathic haemolytic anaemia, ischaemia and widespread organ damage especially in the brain and heart.

The TGA approval of caplacizumab was welcomed by Professor Chris Ward, haematologist at Royal North Shore Hospital, Sydney, who said it would be the first targeted treatment for the approximately 100 reported cases of aTTP each year in Australia.

“Caplacizumab represents a significant advance in the treatment of aTTP as it can block the formation of platelet rich microthrombi that underlie the acute illness,” he said.

“Adding caplacizumab to standard therapy will lower the risk of further thrombotic events or TTP recurrence.”

Professor Chris Ward said clinicians and laboratory staff need to be alert for the combination of falling platelet counts, red cell breakdown (microvascular haemolysis) and sudden organ failure that characterise aTTP.

“In such cases, urgent measurement of ADAMTS13 levels can confirm the diagnosis and guide treatment. Initial treatment of aTTP involves plasmapheresis but patients may develop new vascular events or recur early despite ongoing plasma exchanges.”

A randomised controlled Phase III clinical trial of 145 patients showed that caplacizumab, in conjunction with Plasma Exchange (PEX), and immunosuppression, was associated with faster normalisation of the platelet count; a lower incidence of a composite of TTP-related death, recurrence of TTP, or a thromboembolic event during the treatment period; and a lower rate of recurrence of TTP during the trial than placebo.

According to the product information, treatment should be initiated and supervised by physicians experienced in the management of patients with thrombotic microangiopathies. Caplacizumab is not listed on the PBS.

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