title: Rituximab pharmacokinetics during the management of acute idiopathic thrombotic thrombocytopenic purpura.
abstract: BACKGROUND
  Increasingly, patients with acute, idiopathic, antibody mediated thrombotic thrombocytopenic purpura (TTP) are being treated with rituximab to achieve a durable remission, however, there is the potential that it is removed by plasma exchange (PEX).
  
  
  OBJECTIVE
  To look at the pharmacokinetics and pharmacodynamics of rituximab in patients with acute idiopathic TTP undergoing PEX.
  
  
  METHODS
  Patients who received rituximab for acute idiopathic TTP (group 1, n = 30) and a control group (group 2, n = 3) of TTP patients in remission receiving rituximab electively as maintenance were included. Rituximab levels were measured before/after each infusion, before/after PEX and in follow-up. ADAMTS-13 activity, anti-ADAMTS-13 IgG and CD19% were measured to assess response.
  
  
  RESULTS
  The median number of PEX to remission after rituximab was 10 (range 4-25). In group 1 there was no significant incremental rise in the peak serum rituximab level until dose 4. Trough levels were lower in patients who had had PEX since their last rituximab infusion. In the control group, there was an incremental rise in the peak serum rituximab level and all patients had detectable trough levels. The median fall in rituximab per PEX was 65%. All patients achieved CD19 < 1%. In group 1, the median time to undetectable rituximab was 5 months (range 0-12 months) and to B cell return was 7 months (range 3-24 months). ADAMTS-13 increased and anti-ADAMTS-13 fell after therapy. There were three deaths and two relapses in group 1. Relapse was not temporally related to B cell return.
authors.affiliation: Haemostasis Research Unit, University College London Department of Haematology, London, UK. v.mcdonald@ucl.ac.uk
authors.forename: V
authors.initials: V
authors.lastname: McDonald
authors.forename: K
authors.initials: K
authors.lastname: Manns
authors.forename: I J
authors.initials: IJ
authors.lastname: Mackie
authors.forename: S J
authors.initials: SJ
authors.lastname: Machin
authors.forename: M A
authors.initials: MA
authors.lastname: Scully
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D058846:Antibodies, Monoclonal, Murine-Derived / Q000493:pharmacokinetics* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011697:Purpura, Thrombotic Thrombocytopenic / Q000628:therapy*; D000069283:Rituximab; D055815:Young Adult
chemical_list: D058846:Antibodies, Monoclonal, Murine-Derived; D000069283:Rituximab