OBJECTIVETo evaluate the efficacy and safety of rituximab on B-lymphocytes and anti-platelet glycoprotein-specific antibodies in patients with refractory primary immune thrombocytopenic (ITP).

METHODSThirty-one ITP patients with a median age of 36 years (range 16 - 56 years) received solely intravenous rituximab at the dose of 375 mg/m(2) once weekly for consecutive 4 weeks. Lab studies included complete blood count, serum concentrations of IgG, IgM and IgA. CD3(+), CD4(+), CD8(+), CD19(+) and CD20(+) cell numbers were assayed by flow cytometry and anti-platelet glycoprotein-specific antibodies (GPIIb/IIIa, GPIb/IX) were assayed by monoclonal antibody-specific immobilisation of platelet antigens (MAIPA) prior to and following rituximab therapy. The response was evaluated according to the response criteria of international working group of ITP.

RESULTSComplete responses were achieved in 12 cases, response in 7 cases, and no response in 12 cases. Responses were sustained 2 to 28 months (median 6 months) with 4 cases relapsed. After 4 weeks of rituximab therapy, GPIIb/IIIa and GPIb/IX disappeared in responded patients, and CD 19(+)/CD20(+) cells were almost depleted in all patients. As expected, the serum concentrations of IgG, IgM, IgA, and the T cell counts were not changed after therapy. Four patients developed infusion-related reaction, 1 impaired renal function, and 3 secondary infections.

CONCLUSIONRituximab is effective and safe, and the adverse reaction is tolerable.