Background The loss of response in patients treated with anti-TNFα monoclonal antibodies is relatively frequent. One of the reasons is the development of immunogenicity, causing treatment failure.

Purpose To determine the prevalence of immunogenicity in patients with anti-TNF monoclonal antibodies.

Material and methods We conducted a retrospective observational study, in a reference hospital area. We included all patients with serum levels of adalimumab, infliximab or etanercept determined between May 2015 and September 2017. Serum samples were routinely collected every six months before the drug injection, or when the responsible doctor requests it. Samples were analysed by enzyme-linked immunosorbent assays (ELISA). The variables studied were: sex, age, number of serum samples collected, diagnosis, previous biologic therapy, serum drug concentrations and antibody level. Antibodies were performed in patients who had undetectable concentrations of the drug. We used χ² test to compare the association between categorical variables, using SPSS version 23.0.

Results We included 310 patients (50.3% females, mean age: 46.2 (SD:15.1) years). Five hundred and eighty-two serum levels were collected (36.9% adalimumab, 46.6% infliximab, 16.5% etanercept). The most frequent diagnoses were Crohn’s disease (26.5%), rheumatoid arthritis(19.4%) and ankylosing spondylitis (16.8%).

The 53.4% of patients studied had not received prior treatment with biological drugs, 29.1% were treated with one biological and 17.5% with two or more. The mean serum trough concentrations determined were: infliximab 6 (SD:4.8) mcg/mL, adalimumab 6.4 (SD:4.3) mcg/mL and etanercept 2.2 (SD:2.1) mcg/mL.

The 36.1% of serum trough levels were below the therapeutic range, 44.5% were in range and 19.4% were higher. Antibodies were analysed in 60 patients. Twenty-seven patients presented antibodies, 44.4% against infliximab and 55.6% to adalimumab (p=0.229). No patient with etanercept presented antibodies.

The 85.2% of patients with antibodies had received a previous biologic therapy, compared to 14.8% who had not received previous treatment (p<0.001).

8.7% presented antibodies, and in all cases it was changed to another biological drug.

Conclusion 8.7% of our population has presented antibodies against these drugs, which prevents us gaining a therapeutic objective in these patients: this percentage is lower than the published studies show.¹

The monitoring of biological drug levels and the analysis of antibodies provide an improvement in the management of the patient.

Reference and/or Acknowledgements 1. Hindryckx P, etal. Prevention and management of anti-drug antibodies against therapeutic antibodies in inflammatory bowel disease: a practical overview. Drugs2017;77:363–377.

No conflict of interest