Long-term follow-up of patients with congenital thrombotic thrombocytopenia purpura receiving a plasma-derived factor VIII (Koate) that contains ADAMTS13

Background: Hereditary thrombotic thrombocytopenia purpura (hTTP) is an ultra-rare disorder resulting from an inherited deficiency of ADAMTS13, a von Willebrand factor (VWF)-cleaving metalloprotease. The plasma-derived factor VIII/VWF Koate (FVIII/VWF^Koate ) has been shown to contain ADAMTS13, allowing for its use to treat hTTP at home by the patient/caregiver.

Aim: Based on prior demonstration of safe and effective use of FVIII/VWF^Koate in eight patients with hTTP, we conducted a retrospective study to gather additional data regarding the use of FVIII/VWF^Koate for hTTP.

Methods: This was a multicentre, retrospective, noninterventional chart review of patients who had received FVIII/VWF^Koate for the management of hTTP. Data collected included demographics, medical history, relevant family history, past use and tolerability of fresh frozen plasma, and details regarding FVIII/VWF^Koate therapy.

Results: The cohort included 11 patients (seven males, four females) with hTTP, ranging in age at study entry from 2 to 28 years. The average duration of FVIII/VWF^Koate therapy was 4.8 years (range, 0.5-6.5 years). Among nine patients using FVIII/VWF^Koate as prophylaxis, the normalized annual rate of breakthrough TTP episodes ranged from 0.2 to 1.1 episodes/year. All nine patients who received FVIII/VWF^Koate prophylaxis had thrombocytopenia recorded at baseline, while eight (88.9%) did not have thrombocytopenia after using FVIII/VWF^Koate . There was one AE (unspecified) attributed to FVIII/VWF^Koate .

Conclusion: These data suggest that FVIII/VWF^Koate is a safe and well-tolerated source of the missing ADAMTS13 enzyme in patients with hTTP, producing a marked reduction in thrombocytopenia prevalence, low frequency of TTP episodes, and with the added benefit of self- or caregiver-administration.