Etanercept is a human therapeutic Monoclonal Antibody that targets tumour necrosis factor alpha (TNFα).
In Rheumatoid Arthritis (RA), the use of MAb therapy requires a personalised approach. The long term effectiveness of anti-TNFα agents such as Etanercept, is strongly influenced by its bioavailability, pharmacokinetics and immunogenicity.
Clinical trials have shown that over time a high proportion of patients lose response to treatment. In recognition of this phenomenon and in an attempt to better understand the course of disease there has been an increase in the use of therapeutic drug monitoring. Measuring serum trough drug levels to ensure an adequate drug concentration is maintained within a defined 'therapeutic window' is important for achieving clinical remission.
Failure to respond to biological treatments during the induction phase, or losing response during the maintenance phase, can be attributed to immunogenicity. Anti-TNFα Blockers (e.g. Etanercept and biosimilars) 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.
Anti-drug antibodies can also be measured in serum to help provide a more complete clinical picture as to why a patient may have lost control of their disease. A combination of therapeutic drug and anti-drug antibody monitoring provides a potential to preempt the course of disease, predict disease outcome, and to personalise a treatment strategy.
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 Etanercept in Rheumatoid Arthritis may deliver similar beneficial results.