Rituximab (Mabthera®) or its biosimilar - Therapeutic Drug Monitoring (TDM)

Binding of rituximab to CD20 causes death of B-lymphocytes. Rituximab binds specifically to the transmembrane antigen, CD20, a non-glycosylated phosphoprotein, located on pre-B and mature B lymphocytes, both on normal and malignant cells. The Fab domain of rituximab binds to the CD20 antigen on B lymphocytes and the Fc domain can recruit immune effector functions to mediate B cell lysis. Possible mechanisms of effector-mediated cell lysis include complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity.

Clinical Use

In Europe, used to treat the following blood cancers and inflammatory conditions:

  • follicular lymphoma and diffuse large B cell non-Hodgkin’s lymphoma chronic lymphocytic leukaemia
  • severe rheumatoid arthritis
  • granulomatosis with polyangiitis (GPA)
  • microscopic polyangiitis (MPA)

Depending on the condition it is used to treat, rituximab may be given on its own, or with chemotherapy, methotrexate or a corticosteroid.

Testing rituximab concentration:

The assay is performed using Enzyme Linked Immunosorbent Assay (ELISA). The limit of quantification (LOQ) for rituximab in serum is 0.005 µg/mL.

Testing rituximab anti-drug antibodies (ADA):

The assay is performed using radioimmunoassay (RIA). The limit of quantification (LOQ) for ADA is 12 AU/mL

Clinical Relevance

No response or loss of response of treatment with rituximab.

During treatment, some patients may develop antibodies to rituximab; anti-drug antibodies (ADA).

With level testing of biologics, efficacy of therapy can be improved, as treatment decisions may need to be adapted depending on the test results in conjunction with clinical responses to treatment.

Data and interpretation of rituximab ADA and its serum levels are still very limited.

Personalized Medicine

Monitoring biologic levels in individual patients allows optimization of treatment efficacy by adjusting therapy depending on the specific response of the patient. When drug levels are decreased in a non-responder, this may reflect formation of inactivating antibodies directed to the biologic treatment. Immunogenicity testing identifies presence or absence of inactivating antibodies, which guides the next treatment decision – switch to other biological treatment, lowering of dose or intensify dosing. Reducing drug dosage in well-responding patients with relatively high drug levels cuts down cost. A personalized approach can improve therapy efficacy and quality of life.

Read more on the following pages:

Order of test: Print and complete the request form and send it together with the sample.

For further questions please contact us.

To receive more information about drug monitoring please visit www.svarlifescience.com

20 years experience