Using Adalimumab Serum Concentration to Choose a Subsequent Biological DMARD in Rheumatoid Arthritis Patients Failing Adalimumab Treatment: a Blinded Randomized Superiority Trial

Over the last decades biopharmaceuticals such as agents against tumor necrosis factor (TNF), are frequently prescribed to optimize rheumatoid arthritis treatment. Although TNFi such as adalimumab, etanercept and infliximab, have improved the treatment of rheumatoid arthritis, a proportion of patients discontinue the treatment because of inefficacy or intolerance.

Where TNFi have failed, mainly two treatment approaches are available: switch to another TNFi or to a biological with a different mode of action (notably rituximab, abatacept or tocilizumab) or to a target synthetic DMARDs. The EULAR recommendation for the management of rheumatoid arthritis advocate that any biologic agent including a subsequent TNFi can be used with equal chance for effect in case of non-response to a previous TNFi. This recommendation is based on three randomized controlled trails, but it should be noted that systematic reviews also including non-randomized controlled studies sometimes concluded that non-TNFi are more effective after TNFi failure than a second TNFi.

Of note, currently there are no strong predictors available for response to bDMARDS in RA. This study focuses on non-response after adalimumab, as this is the most prescribed TNFi worldwide.

Although it seems that indeed on a group level response to a non-TNFi is comparable to a second TNFi after the first TNFi has failed, using therapeutic drug monitoring could identify subgroups of patient who would benefit more from either a non-TNFi or a TNF-i as next treatment. The underlying pathophysiological mechanisms for this hypothesis are explored in this study.

Nonresponse on adalimumab in RA can have different causes. Firstly, the patient might not be sensitive to TNF blockade at all, or the patient develops this trait later on (primary nonresponse or secondary nonresponse). In these patients, switching to a non-TNFi might conceptually be superior to starting a second TNFi. However, in other patients nonresponse (either primary or secondary) might be caused by inefficient drug concentration because of development of antidrug antibodies against adalimumab. In these patients a TNFi might be just as effective as a non-TNFi, as these patients have drug- but not class failure. Thus, testing of adalimumab levels might be helpful in channelling patients to their most optimal treatment.