P337 Proactive therapeutic drug monitoring of Adalimumab, but not HLADQ*A1 determination, predicts inflammatory bowel disease outcome and persistence of treatment

Abstract

Abstract Background Anti-TNF drugs have proven effective in managing Inflammatory Bowel Disease (IBD), but a significant percentage of patients exhibit primary or secondary non-response. Therapeutic drug monitoring (TDM) is a valuable tool for optimizing patient management. HLA-DQA1*05 gene has been investigated as a potential marker for immunogenicity and loss of response to anti-TNF therapy.This prospective, multicentric study aimed to assess the clinical impact of determining Adalimumab (ADA) levels and anti-adalimumab antibodies (Abs) in IBD patients and the influence of the HLA-DQA1*05 allele on the response and maintenance of ADA treatment over a 24-month follow-up. Methods Patients initiating ADA treatment between October 2020 and October 2022 were enrolled. Demographic data and IBD characteristics were recorded. Clinical Activity Index, C reactive protein (CRP), faecal calprotectin (FC), endoscopy or radiological activity, Global Physician Assesment (GPA) and PRO (by IBDQ-9) were prospectively collected at baseline and at the same time that ADA levels: week 4, 10, 30 and 12 months. HLA-DQA1*05 was genotyped at baseline. Pearson coefficient was utilized to assess correlations between ADA levels and disease activity. Results We included 170 (age 42±17 years, 54% female) IBD patients (74% Crohn`s Disease, 24% Ulcerative Colitis and 2% Indeterminate colitis) who started ADA (85% naïve to anti-TNF). At baseline, 80% had an active disease (GPA=1); CRP and FC were 10.72 ±17.85 mg/L and 568 ±775 µg/g; PRO at baseline was 63±8.6. HLA was determined in 167 patients, of whom 71 (42%) were HLA-DQA1*05 positives. Median follow up was 17 months. No correlation between HLA and drug levels or Abs was founded. ADA levels at the end of induction was correlated with ADA levels during follow up. ADA serum concentration >7 µg/mL at weeks 4 and 10 correlated with improved clinical response at corresponding time points (p<0.001). Patients with ADA levels >7 µg/mL at week 10 demonstrated better disease control at 12 months. 41 patients stopped ADA. It was associated with active disease, low ADA levels, and adverse clinical and laboratory markers. HLA-DQA1*05 positivity did not correlate with adverse reactions or Abs during the observational period. A significative improvement in PROs in patients who started treatment with ADAL (62.73 at baseline and 69.42 at week 30) (p<0.001) was observed. Conclusion Early Drug level monitoring of Adalimumab may improve the management of IBD patients. PCR, CF and GPA at week 10 may predict treatment failure. ADA levels >7 µg/mL is associated with a better clinical response in short and long-term, independent of HLADQA1*05.