Prophylactic efficacy of rhADAMTS13. Before the challenge with 2000 VWF:RCoU/kg BW of rhVWF, one group of animals received 200 FRETS-U/kg BW rhADAMTS13 (rhA13 + rhVWF), whereas the control group received rhVWF only (rhVWF). Platelet counts were determined after 1 day. Whereas all animals of the control group developed a severe thrombocytopenia (●), animals prophylactically treated with rhADAMTS13 (▴) were protected.