Congenital thrombotic thrombocytopenic purpura (cTTP) is an ultra-rare disorder characterized by thrombocytopenia, microangiopathic hemolytic anemia, and ischemic organ damage caused by pathogenic ADAMTS13 variants. ADAMTS13 containing product including fresh frozen plasma (FFP) and plasma-derived Factor VIII concentrates are commonly used to supply ADAMTS13
however, frequent hospital visits and allergic reactions are major drawbacks. A recombinant ADAMTS13 (rADAMTS13) was recently developed to address these issues. However, real-world evidence has not been reported owing to the rarity of this condition. This study compared the efficacy and safety of FFP and rADAMTS13 in 14 Japanese patients, including five patients with end-stage renal disease who were excluded from the phase III trial. The median peak level of ADAMTS13 activity 15 min after rADAMTS13 administration was significantly higher than that after FFP (68.4% vs. 15.9%, p<
0.001). ADAMTS13 activity 1 week after rADAMTS13 administration was well maintained compared with FFP infusion (11.6% vs. 5.1%, p<
0.001). Patients reported no allergic reactions after rADAMTS13 administration and appreciated the convenience of a single infusion of rADAMTS13, suggesting that rADAMTS13 is a safe and effective alternative to FFP in patients with cTTP. This is the first publication of patients with cTTP who switched FFP to novel rADAMTS13 from Japanese real-world-data.