Inhibition of von Willebrand factor–platelet glycoprotein Ib interaction prevents and reverses symptoms of acute acquired thrombotic thrombocytopenic purpura in baboons

The pathophysiology of thrombotic thrombocytopenic purpura (TTP) can be explained by the absence of active ADAMTS13, leading to ultra-large von Willebrand factor (UL-VWF) multimers spontaneously interacting with platelets. Preventing the formation of UL-VWF–platelet aggregates therefore is an attractive new treatment strategy. Here, we demonstrate that simultaneous administration of the inhibitory anti-VWF monoclonal antibody GBR600 and the inhibitory anti-ADAMTS13 antibody 3H9 to baboons (prevention group) precluded TTP onset as severe thrombocytopenia and hemolytic anemia were absent in these animals. In addition, partial VWF inhibition was not enough to prevent thrombocytopenia, demonstrating the specificity of this therapeutic strategy. GBR600 treatment of baboons during acute TTP (treatment group) resulted in a rapid recovery of severe thrombocytopenia similar to the platelet count increases observed in TTP patients treated by plasma exchange. Baboons in the control group only injected with 3H9 developed early stages of TTP as previously described. Hence, inhibiting VWF-GPIb interactions is an effective way to prevent and treat the early symptoms of acquired TTP in baboons.