Study of the Influence of Plasma Exchange on the Pharmacokinetics of Rituximab

Twenty patients will be enrolled: ten patients treated by rituximab and ten patients treated by rituximab and plasma exchange. The plasma concentration of rituximab and the efficacy of the treatment will be compared between the two groups of patients.

The enrollment in the study will not change the treatment of patients except for blood sampling.

Each patient will undergo fifteen blood samples between the start of infusion of rituximab and three months after the start of infusion. For the patients who will undergo plasma exchange, three additional blood samples will be performed at each plasma exchange (at the start, at the end and one day after the plasma exchange) and a sample of the plasma exchanged will be keep.

The plasma concentration of rituximab will be determined by ELISA method (Enzyme Linked ImmunoSorbent Assay) The pharmacokinetic analyse will consist in the determination of the Area Under the Concentration Curve (AUC) by a non compartmental approach.

The AUC levels will be compared (using the t Student test) between the two populations of patients (patients treated by rituximab, versus patients treated by rituximab and plasma exchange) The efficacy of the treatment will be evaluated by the CD19+ B Cell count.

Inclusion criteria

• Patient who should be treated by rituximab for various autoimmune diseases or humoral acute rejection of renal transplant
• Patient older than 18 years old
• Patient who have signed the written informed consent form

Exclusion criteria

• Patient presenting a contra indication to rituximab (hypersensitivity, active infection, severe cardiac failure (NYHA class IV))
• Blood sampling impossibility
• Pregnant or breasting women