Introduction Therapeutic failures with biologic drugs in inflammatory bowel disease (IBD) pose a significant challenge for clinicians who manage patients with IBD. There is a paucity of data demonstrating clinically relevant threshold levels of IFN and ADA. Small studies have shown that high IFN trough levels and low antibody levels were associated with successful maintenance of remission. For ADA the role of monitoring drug levels is less clear with considerable overlap trough serum levels between those in remission and in those not achieving remission.
Method A retrospective review of all therapeutic drug level (INF and ADA) monitoring for 12 months in the 2014. Clinical characteristics included demographics. We also collected data on IBD type, duration, distribution and activity. We monitored INF and ADA trough levels, antibody trough levels, presence of concomitant immunosuppression and outcome of drug monitoring.
Results In total thirty-eight IBD (95% Crohn’s disease; n = 36) patients had drug level monitoring (74% receiving IFN n = 28; 26% receiving ADA n = 10) for the following indications: (i) 13% primary nonresponse (n = 5); (ii) 58% secondary loss of response (n = 22) and; (iii) 29% other indication (n = 11).
Antibodies were detectable in 21% (n = 8) of patients. Drug monitoring led to 34% (n = 13) patients continuing drug without any modification; 45% (n = 17) escalated dose or interval; 8% (n = 3) switched biologic therapy; 10% (n = 4) underwent surgery. None of the ADA patients were receiving concomitant immune suppression, however the use of Azathioprine (AZA) and IFN was associated with a lower incidence of antibody formation (10% vs. 24%; p < 0.05).
Conclusion The burden of biologic drug and antibody monitoring in a UK DGH IBD unit is small, but is advantageous to enable prompt optimisation of therapy. The results are optimisation of therapy and recapture of response in over half of patients on long-term biologic agents for maintenance of remission of IBD.
Disclosure of interest None Declared.