Rituximab Drug Level

Immunology

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Description

Rituximab is a chimeric monoclonal antibody directed against the B cell surface antigen CD20. It is used for the therapy of lymphomas and different autoimmune diseases (e. g. rheumatoid arthritis, granulomatosis with polyangiitis, immune thrombocytopenia, myasthenia gravis) [1, 2, 3, 4].

CD20 is a surface antigen on pre-B cells and mature B cells, but it is not expressed on hematopoietic stem cells, pro-B cells, plasma cells or cells of other tissues. CD20 supports the B cell immune response, in particular against T-cell-independent antigens.

By binding to CD20, rituximab improves the effect of natural killer (NK) cells which induce cell death in the B cells marked with rituximab. In autoimmune disease therapy, the reduction of B cells results in a reduction of autoantibodies, leading to a reduction of the symptoms [5].

Monitoring rituximab drug level can determine if the serum or plasma level is within the optimal therapeutic range. The results help the treating physician to monitor and optimise the therapy. It is recommended that ideal trough level is >25 ng/mL for the drug to be effective [1, 2].

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Indications

Monitoring trough Rituximab levels.

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Sample Type

2mL Serum (Gel 5mL Yellow tube) or 2mL Plasma (EDTA). Requests from outside Sheffield: Transport at ambient temperature via Royal Mail or Courier.

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Reference Range

Ideal trough level is >25 ug/mL. Levels below this indicates that Rituximab is insufficient or has not been given.

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Turnaround Time

10 days

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Testing Frequency

As required

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References

Jager U, Fridrik M, Zeitlinger M, et al. Rituximab serum concentrations during immuno-chemotherapy of follicular lymphoma correlate with patient gender, bone marrow infiltration and clinical response. Haematologica, 2012, 97(9): 1431 – 1438. [Ref 1] Jaeger U, Kreiger O, Hopfinger G, et al. Two-monthly Rituximab infusions maintain target concentrations: Pharmacokinetic data of the AGMT-NHL9 maintenance study in patients with follicular lymphoma in complete or partial remission. Blood, 2008, 112(11). [Ref 2]. Falchi L, Ferrajoli A, Jacobs I, Nava-Parada P. An Evidence-based Review of Anti-CD20 Antibody-containing Regimens for the Treatment of Patients With Relapsed or Refractory Chronic Lymphocytic Leukemia, Diffuse Large B-cell Lymphoma, or Follicular Lymphoma. Clinical lymphoma, myeloma & leukemia. 2018 Aug;18(8):508–518.e14. [Ref 3] Cohen SB, Emery P, Greenwald MW, Dougados M, Furie RA, Genovese MC, et al. Rituximab for rheumatoid arthritis refractory to anti-tumor necrosis factor therapy: Results of a multicenter, randomized, double-blind, placebo-controlled, phase III trial evaluating primary efficacy and safety at twenty-four weeks. Arthritis and rheumatism. 2006 Sep 1;54(9):2793–806. [Ref 4] Rudnicka D, Oszmiana A, Finch DK, Strickland I, Schofield DJ, Lowe DC, et al. Rituximab causes a polarization of B cells that augments its therapeutic function in NK-cell-mediated antibody-dependent cellular cytotoxicity. Blood. 2013 Jun 6;121(23):4694–702. [Ref 5]

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