Adalimumab therapeutic drug monitoring in hidradenitis suppurativa

Summary: Abstract Body: Hidradenitis suppurativa (HS) is a chronic inflammatory condition. While adalimumab (ADM) is an effective treatment for moderate-to-severe cases, about 50% of patients lose response after 36 weeks. Therapeutic drug monitoring (TDM) optimizes treatment by assessing ADM levels and anti-drug antibodies (ADAs). This observational, single-center study enrolled 46 adult patients with moderate-to-severe HS on ADM therapy from January 2023 to May 2024 at a HS specialty clinic, evaluating serum ADM levels and clinical outcomes after a minimum period of 8 weeks. Most participants were female (60.9%) with a median age of 38. Clinical responses were assessed by changes in lesion count and categorized as: Low (<50%), Partial (50-75%), or High (>75%) improvement. Statistical analyses included Spearman’s rank correlation, Pearson’s correlation, and the Wilcoxon-Mann-Whitney tests. Serum ADM levels were correlated with clinical response (r = 0.43, p = 0.002). Low responders had lower ADM level (9.14 vs. 24.6 µg/mL; p = 0.007) and higher drug clearance (0.94 vs. 0.37 L/day; p < 0.001). ADAs detected in 10 patients, which were associated with lower ADM levels (10 vs. 17 µg/mL; p = 0.03) and increased drug clearance (1.048 vs. 0.406 L/day). No ADA-positive patients achieved a high responders. The HLA-DQA1*05 allele was linked to ADA development (83% vs. 19%; p = 0.001). High responders showed longer drug survival (146 vs. 45 weeks) and lower hsCRP levels (1.9 vs. 18.3 mg/L). Higher ADM levels and the absence of ADAs are associated with improved outcome in HS patients on maintenance ADM therapy. Elevated ADM levels correlated with better clinical outcomes, lower inflammation, and extended drug survival. However, the presence of ADAs was linked to increased drug clearance, lower ADM levels, and diminished therapeutic efficacy. Maneli Doroudian Tehrani^{1, 2}, Stella Chen³, Bruna Wafae^{1, 2}, Thierry Dervieux⁴, Alexa Kimball^{1, 2}, Martina Porter^{1, 2} 1. Dermatology, Beth Israel Deaconess Medical Center, Boston, MA, United States. 2. Dermatology, Harvard Medical School, Boston, MA, United States. 3. Dermatology, Mayo Foundation for Medical Education and Research, Rochester, MN, United States. 4. Prometheus Laboratories Inc, San Diego, CA, United States. Clinical Research: Epidemiology and Observational Research