Study to Assess Efficacy and Safety of Anti-von Willebrand Factor (vWF) Nanobody in Patients With Acquired Thrombotic Thrombocytopenic Purpura (aTTP)

Inclusion Criteria: * 18 years of age or older (adults) or aged 12 to \< 18 years (adolescents) * Male or female subject, willing to accept an acceptable contraceptive regimen * Subject with a clinical diagnosis of TTP * Requiring PE (one single PE session prior to randomization into the study was allowed) * Subject accessible to follow-up * Subject able to provide signed and dated informed consent and assent (if applicable, for adolescents) Exclusion Criteria: * Platelet count ≥ 100,000/µL * Severe active infection indicated by sepsis (requirement for pressors with or without positive blood cultures) * Clinical evidence of enteric infection with Escherichia coli 0157 or related organism * Anti-phospholipid syndrome * Diagnosis of disseminated intravascular coagulation (DIC) * Pregnancy or breast-feeding * Hematopoietic stem cell or bone marrow transplantation-associated thrombotic microangiopathy * Known with congenital TTP * Active bleeding or high risk of bleeding * Uncontrolled arterial hypertension * Known chronic treatment with anticoagulant treatment that cannot be stopped safely, including but not limited to: * vitamin K antagonists * heparin or low molecular weight heparin (LMWH) * non-acetyl salicylic acid non-steroidal anti-inflammatory molecules * Severe or life threatening clinical condition other than TTP that would impair participation in the study * Subjects with malignancies resulting in a life expectation of less than 3 months * Subjects with known…