Rituximab maintenance for relapsed refractory thrombotic thrombocytopenic purpura

BACKGROUND: Rituximab, an anti-CD20 chimeric monoclonal antibody, has been used successfully to treat patients with relapsed or refractory thrombotic thrombocytopenic purpura (TTP); however, the optimal dose and frequency and the role of rituximab maintenance remain uncertain. STUDY DESIGN AND METHODS: We describe a 45-year-old woman with chronic relapsing immune thrombocytopenia who responded to rituximab retreatment administered in four doses over the course of 12 months. Previously, she had received four doses of rituximab and sustained a remission for 19 months. During her latest TTP relapse, multiple treatments were administered including rituximab retreatment. After the first dose (375 mg/m2), she developed serum sickness requiring further doses to be deferred. Three subsequent doses were administered at 4-month intervals over the course of 12 months. ADAMTS13 activity was measured by von Willebrand factor (VWF) digestion. ADAMTS13 inhibition was measured by a modification of the VWF digestion assay and anti-ADAMTS13 antibodies were measured by enzyme-linked immunoassay (enzyme-linked immunosorbent assay, American Diagnostica). RESULTS: Clinical and laboratory remission were achieved after one dose of rituximab, with normalization of ADAMTS13 activity and disappearance of ADAMTS13 inhibitor. Three subsequent doses of rituximab were given without incident and the patient remained in remission after 3.5 years of follow-up (2.5 years since her last dose of rituximab). CONCLUSION: Maintenance dosing of rituximab should be considered in some patients with relapsing TTP.