The significance of serum anti-rituximab (anti-CD20 monoclonal antibody)‎ antibodies in treatment response of patients with B-cells malignancy

Abstract EN

Background: The chimeric anti-CD20 monoclonal antibody, rituximab, is an effective therapeutic agent used for treating patients with B- cell disorders, however there is a significant variation in therapy response among patients and relapse is common.

Furthermore, it is unclear why a class of patients is initially not responding and other responding become refractory and later resistant to further treatment.

Aim: To study the significance of serum anti- rituximab antibodies in the patients initially responding to the treatment and became refractory and resistant to the treatment.

Patients and Methods: Serum samples were obtained from forty two patients with B- cells disorders after getting their consent, the serum samples were tested for the serum anti- rituximab antibodies by enzyme linked immunosorbant assay (ELISA).

They received rituximab at initial dose of 375 mg/m2 and a maintenance dose of 500 mg/m2 .

The serum samples were obtained from each patient after subsequent doses of treatment.

Results: The patients’ ages ranged between 20 -80 years.

The response rate 50 days after treatment initiation was 40(95%).

During the first year of treatment, the complete remission was found in 33(75%) of the patients and 9(21%) of the patients developed the non responsiveness to treatment.

The serum level of anti- rituximab antibodies was detected among 15(36%) of the patients, only 2(22%) of them were among the 9 patients who developed the treatment non responsiveness and the other 13(39%) were among the complete remission patients with no significant difference statistically.

Conclusion: In conclusion, these results indicate that there was no significant association between the level of the serum anti rituximab antibodies and the response to rituximab treatment.

Recommendations: We recommend to include a lager sample size of patients receiving retuximab for treating diseases other than B cells disorders rheumatoid arthritis, SLE and multiple sclerosis patients.