Efficacy of a rituximab regimen based on B cell depletion in thrombotic thrombocytopenic purpura with suboptimal response to standard treatment: Results of a phase II, multicenter noncomparative study.

The standard four-rituximab infusions treatment in acquired thrombotic thrombocytopenic purpura (TTP) remains empirical. Peripheral B cell depletion is correlated with the decrease in serum concentrations of anti-ADAMTS13 and associated with clinical response. To assess the efficacy of a rituximab regimen based on B cell depletion, 24 TTP patients were enrolled in this prospective multicentre single arm phase II study and then compared to patients from a previous study. Patients with a suboptimal response to a plasma exchange-based regimen received two infusions of rituximab 375 mg m-2 within 4 days, and a third dose at day +15 of the first infusion if peripheral B cells were still detectable. Primary endpoint was the assessment of the time required to platelet count recovery from the first plasma exchange. Three patients died after the first rituximab administration. In the remaining patients, the B cell-driven treatment hastened remission and ADAMTS13 activity recovery as a result of rapid anti-ADAMTS13 depletion in a similar manner to the standard four-rituximab infusions schedule. The 1-year relapse-free survival was also comparable between both groups. A rituximab regimen based on B cell depletion is feasible and provides comparable results than with the four-rituximab infusions schedule. This regimen could represent a new standard in TTP. This trial was registered at www.clinicaltrials.gov (NCT00907751). Am. J. Hematol. 91:1246-1251, 2016.