Objective: To evaluate the efficacy and safety of rituximab on B-lymphocytes and anti-platelet glycoprotein-specific antibodies in patients with refractory primary immune thrombocytopenic (ITP).
Methods: Thirty-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.
Results: Complete 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.
Conclusion: Rituximab is effective and safe, and the adverse reaction is tolerable.