Utility of Measuring Adalimumab Drug Levels and Anti-Drug Antibodies in Clinical Practice: A Large IBD Referral Centre Experience
Introduction: The development of adalimumab (Ada) drug and antibody testing has allowed a personalised approach to complex inflammatory bowel disease (IBD) treatment. We present our 2-year experience at a tertiary IBD referral centre.
Method: All Ada drug and antibody levels carried out at Guy’s and St. Thomas’ Hospital were analysed. The indications for carrying out levels, the subsequent changes in management and the long-term patient outcomes were evaluated.
Results: 143 levels were carried out on 105 patients from October 2012 to October 2014. The median value was 5 μg/ml (range 0- >8 μg/ml). 74 levels (52%) were done on patients who had symptoms indicative of loss of response (LOR). 13 patients, all with no detectable antibodies had their dose increased, 10 of these patients had low levels (<5.0 μg/ml), 6 of whom responded. 1 patient had high levels of antibodies and therefore Ada was stopped. A further 8 patients had their Ada stopped and were referred for surgery or switched to infliximab. 5 levels (4%) were measured after induction (week 12–14) resulting in 1 patient with a low level (3.5 μg/ml) and clinically active disease escalating to 40 mg weekly with good response. 38 levels (27%) were done as part of annual reassessment resulting in only 2 changes in management: 1 patient had dose de-escalation from weekly to every other week due to levels >8 μg/ml and the other had their dose increased to weekly due to low levels (1.4 μg/ml). The remaining levels were done to aid decisions regarding discontinuation of concomitant immunosuppressant (1%), dose de-escalation (11%) and discontinuation of Ada (2%), or to assess response to dose escalation (3%). 39 (27%) of the levels were sub therapeutic in 32 patients. In the 30 patients that did not have antibodies to Ada, 13 patients underwent dose escalation. Ada antibodies were detected in only 2 patients (1%). 1 patient, who had previously had a reaction to infliximab continued on Ada with minimal improvement in her symptoms. The other patient was lost to follow-up shortly after the levels were tested.
Conclusion: Measuring Ada levels in our cohort resulted in a change of management for 25% of patients, a percentage similar to that seen for infliximab. The majority of patients with LOR who had sub therapeutic levels responded well to Ada dose escalation. Antidrug antibody development is infrequent in our
cohort of patients.
