Rituximab is a chimeric therapeutic Monoclonal Antibody that targets B-cells (CD-20) in the treatment of Rheumatoid arthritis, non-Hodgkin's B-cell lymphomas, lymphocytic leukaemia, active granulomatosis with polyangiitis and microscopic polyangiitis.
The use of MAb therapy requires a personalised approach because the long term effectiveness is strongly influenced by bioavailability, pharmacokinetics and immunogenicity. In recent years there has been an increase in the use of therapeutic drug monitoring involving the measurement of serum trough drug levels to ensure an adequate drug concentration is maintained within a defined 'therapeutic window'. This is considered to be important for achieving and maintaining clinical remission.
Some patients will respond well with fewer symptoms and a reduction of inflammatory biomarkers (e.g. CRP) and Disease activity scores, while others may fail to respond during the induction phase of treatment, or lose response over time. Failure to respond to biological treatments during the induction phase, or losing response during the maintenance phase, can be attributed to immunogenicity. Rituximab may trigger immunogenic responses in individuals which can reduce the serum concentration of available drug thus altering its effectiveness.
Anti-Drug-Antibodies (ADA), impede drug activity and may cause severe allergic reactions too and so concomitant immunosuppressants may be used to reduce antibody formation, but it is not always indicated.
In IBD management, studies have shown that therapeutic drug monitoring strategies for infliximab and adalimumab are cost effective and significantly change the clinical decision-making when managing the disease. Similar strategies for monitoring Rituximab in its indicated diseases may deliver similar beneficial results.