en Clinical Medicine Clinical Medicine مقاله پژوهشی Original Research Article <p style="text-align: justify;"><span style="font-size:16px;"><span style="font-family:Times New Roman;"><b><span style="background:#2d7f8f"><span style="color:white">Background & Objective:</span></span><b> </b></b><span style="color:black">Infliximab (IFX) is a chimeric monoclonal antibody that targets tumor necrosis factor-alpha (TNF-&alpha;) and is widely used in the treatment of autoimmune diseases, including rheumatoid arthritis (RA). However, therapeutic responses to infliximab vary among patients. The formation of anti-infliximab antibodies (AIA) may contribute to reduced efficacy and treatment failure. This study aimed to investigate the relationship between AIA formation, infliximab trough levels, and treatment response in patients with RA.</span><br> <b><span style="background:#2d7f8f"><span style="color:white"><span style="letter-spacing:-.1pt">&nbsp;Materials & Methods:</span></span></span></b> <span style="color:black"><span style="letter-spacing:-.1pt">This cross-sectional study included 83 RA patients receiving infliximab (Remicade or Remsima) infusions at &le;&nbsp;6 months. Blood samples were<b> </b>collected prior to IFX infusion. Enzyme-linked immunosorbent assay (ELISA) kits were used to measure AIA, and infliximab trough concentration.</span></span><br> <b><span lang="EN-IN"><span style="background:#2d7f8f"><span style="color:white">Results: </span></span></span>&nbsp;</b><span style="color:black"><span style="letter-spacing:-.1pt">Despite concurrent methotrexate therapy, many patients developed AIA (43.3 %). Infliximab trough concentration was higher in responders than non-responders but statistically not significant (<i>P-value</i>=0.114). Patients aged &le;40 years demonstrated a treatment response rate of 84.6%, compared with only 28.6% among those >60 years (<i>P-value</i> = 0.36). Additionally, male patients showed a higher response rate than females (<i>P-value</i> = 0.12).</span></span><br> <b><span style="background:#2d7f8f"><span style="color:white">Conclusion: </span></span>&nbsp;</b><span style="color:black">The presence of AIA was associated with reduced treatment response in RA patients receiving infliximab. Higher infliximab trough levels correlated with better clinical outcomes. Age and sex may influence treatment efficacy, with younger patients and males showing better responses. Monitoring AIA and drug levels could help optimize therapeutic strategies in RA.</span></span></span></p> Anti-infliximab Antibodies, Infliximab, Remicade, Remsima, Rheumatoid Arthritis, Serum Trough 229 236 http://journal.zums.ac.ir/browse.php?a_code=A-10-7378-1&slc_lang=en&sid=1 Sura Mohammed Lateef sura.sura417@gmail.com 5200319475328460087415 0009-0009-6779-8719 Yes Department of Microbiology, College of Medicine, Al-Nahrain University, Kadhimiya, Baghdad, Iraq Ahmed Abdul-Hassan Abbas ahmed26770@yahoo.com 5200319475328460087416 5200319475328460087416 No Department of Microbiology, College of Medicine, Al-Nahrain University, Kadhimiya, Baghdad, Iraq Mohammed Hadi Alosami mohammad_alosami@yahoo.com 5200319475328460087417 5200319475328460087417 No College of Medicine, Baghdad University, Baghdad, Iraq