Background and importance Inflammatory bowel disease (IBD) is characterised by a chronic inflammation of the gut mucosa. About one-third of patients show primary non-response to biological agents, and up to 50% after an initial clinical response discontinue therapy due to secondary loss of response or a serious adverse event.

Therapeutic drug monitoring (TDM) plays an important role in optimising therapy for these patients.

Aim and objectives Assessing the outcome of optimising biologic drug therapy regimens based on serum dosing results in IBD patients.

Material and methods An observational, descriptive and retrospective study was conducted from 1 April 2018 to 31 August 2021. It included all the patients with IBD treated with biological agents (adalimumab, infliximab and vedolizumab), and this study was based on information contained in pharmaceutical records and clinical files.

A total of 71 patients were included. The study analysed the average treatment times of each drug in patients considered primary non-responders (PNR), as well as patients with secondary loss of response (SLR) to biological agents and the subsequent therapeutic optimisation (dose escalation, interval reduction or therapeutic switch).

Results 58 patients remained in the first line of treatment. 12 patients needed one switch and 1 patient underwent 2 switches. The average number of drugs administered per patient was 1.2.

The overall mean times, in weeks of treatment, were 187 for adalimumab, 94 for infliximab, and 58 for vedolizumab. Patients who remained on the same drug showed a mean treatment time of 193 weeks for adalimumab and 106 for infliximab.

Regarding PNR, it only occurred with infliximab, in 8.1% (3/37) of patients, after an average of 35 weeks of treatment.

20 patients (28%) had undergone 23 therapeutic optimisations by SLR, distributed as follows: 6 increased doses, 2 reduced time interval and 15 therapeutic switches. The time to SLR was, in weeks, 189.5 for adalimumab, 53.3 for infliximab and 18 for vedolizumab.

Conclusion and relevance TDM allowed therapeutic optimisation of biological agents, enabling the maintenance of patients on the selected regimen for more time, and an early switch in PNR.

Serum determination of drug concentrations and antidrug antibody levels may be a good strategy for maintenance and/or optimisation of therapy.

References and/or acknowledgements 1. DOI: 10.1016/j.cgh.2019.03.037

Conflict of interest No conflict of interest