Rituximab and intermediate-purity plasma-derived factor VIII concentrate (Koate®) as adjuncts to therapeutic plasma exchange for thrombotic thrombocytopenic purpura in patients with an ADAMTS13 inhibitor.

Thrombotic thrombocytopenic purpura (TTP) results from a congenital or acquired deficiency of the von Willebrand factor (vWF)-cleaving protease ADAMTS13. The disease can be fatal and hence treatment should be initiated promptly. Therapeutic plasma exchange (TPE) remains the standard treatment along with adjunct therapies including steroids and immunosuppressive drugs. Addition of rituximab to TPE has been shown to be beneficial in refractory/relapsing TTP; however, TPE results in removal of rituximab from the circulation requiring more frequent dosing of rituximab to achieve a favorable outcome. The intermediate-purity plasma-derived Factor VIII concentrate (FVIII) Koate® contains the highest amount of ADAMTS13 activity yet reported and has been used successfully in treating congenital TTP. Here we report our experience with addition of this FVIII concentrate to rituximab, corticosteroids and TPE in three TTP patients with an ADAMTS13 inhibitor to permit withholding TPE for 48 h after rituximab infusion.