Efficacy and safety of first-line rituximab in severe, acquired thrombotic thrombocytopenic purpura with a suboptimal response to plasma exchange. Experience of the French Thrombotic Microangiopathies Reference Center.

OBJECTIVE: To assess the efficacy and safety of rituximab in adults responding poorly to standard treatment for severe autoimmune thrombotic thrombocytopenic purpura.

DESIGN: Open-label prospective study. Outcomes in the survivors were compared to those of 53 historical survivors who were given therapeutic plasma exchange alone or with vincristine.

SETTING: Hospitals belonging to the Reference Network for Thrombotic Microangiopathies in France.

PATIENTS: Twenty-two adults with either no response or a disease exacerbation when treated with intensive therapeutic plasma exchange.

INTERVENTION: Add-on rituximab therapy, four infusions over 15 days.

MEASUREMENTS AND MAIN RESULTS: One patient died despite two rituximab infusions. In the rituximab-treated patients, the time to a durable remission was significantly shortened (p = .03), although the plasma volume required to achieve a durable remission was not significantly different compared to the controls. Platelet count recovery occurred within 35 days in all 21 survivors, compared to only 78% of the historical controls (p < .02). Of the rituximab-treated patients, none had a relapse within the first year but three relapsed later on. In patients treated with rituximab, a rapid and profound peripheral B-cell depletion was produced, lasting for 9 months and correlating with higher a disintegrin and metalloproteinase with thrombospondin-13 activity and lower anti-a disintegrin and metalloproteinase with thrombospondin-13 antibody titers. These differences were no longer significant after 12 months. No severe side effects occurred.

CONCLUSIONS: Adults with severe thrombocytopenic purpura who responded poorly to therapeutic plasma exchange and who were treated with rituximab had shorter overall treatment duration and reduced 1-yr relapses than historical controls.