Objective: To investigate the efficacy and safety as well as the effects of lower dose of rituximab on B-lymphocytes, serum immunoglobulin, and platelet glycoprotein-specific antibodies in patients with chronic refractory immune thrombocytopenic purpura (ITP).
Methods: Twenty chronic refractory ITP patients, median age 47 (20 to 60) years old, received intravenous rituximab at the dose of 100mg once weekly for 4 consecutive weeks. Laboratory studies included complete blood cell count, regular monitoring of liver and kidney functions, blood coagulation and serum concentrations of IgG, IgM and IgA. CD3(+), CD4(+), CD8(+), CD19(+), CD20(+) cell numbers were assayed by flow cytometry prior to and following rituximab. Platelet glycoprotein antibodies were detected by ELISA. The detection of indicators were compared by paired T test, with P < 0.05 as statistically significant.
Results: There was significant difference of the average platelet count between prior- \[(13 ± 5) × 10(9)/L\] and post-treatment \[(124 ± 106) × 10(9)/L\] with lower dose rituximab (P < 0.01). Reaching PLT peak period was of (24 ± 7) d with median time of 18 d. The responses were of 11(55%) CR, 4 (20%) R and 5 (25%) NR, respectively, with median response duration of 8 months (5 - 23 months). There were no significant changes of peripheral blood white blood cell count, hemoglobin, serum immunoglobulin, as well as CD3(+), CD4(+), CD8(+) lymphocyte counts during prior- and post-treatment. CD19(+)/CD20(+) cells were almost depleted in all patients \[(125.65 ± 14.12) × 10(6)/L vs (50.53 ± 29.11) × 10(6)/L, P < 0.01)\]. Expectedly, three cases of positive detection of platelet antibodies were negative after 4 weeks of lower dose of rituximab; one patient experienced infusion-related reaction.
Conclusion: Treatment with lower dose rituximab may be an effective and safe approach in patient with chronic refractory ITP. However, the optimal therapeutic schedule, long-term efficacy and adverse events need further investigation.