Subcutaneous infliximab in the treatment of patients with perianal fistulizing Crohn's disease: current evidence and emerging roles.

Perianal fistulizing Crohn's disease (pfCD), a frequent and serious manifestation of Crohn's disease (CD), is characterized by perianal inflammation and fistula formation and severely impacts patient quality of life. Due to its complex and progressive nature, pfCD requires effective, multidisciplinary management combining both medical and surgical approaches. Infliximab (IFX), a tumor necrosis factor inhibitor, remains the preferred treatment of pfCD. It is recommended in several international clinical guidelines and supported by extensive clinical evidence demonstrating its efficacy and safety in this patient population. Higher IFX serum concentrations have been associated with improved clinical outcomes in CD, reinforcing the need for optimized therapeutic strategies. Subcutaneous (SC) IFX is a more recently available alternative to intravenous (IV) IFX, offering comparable efficacy and safety in patients with CD and greater convenience through self-administration. Although SC IFX has not been evaluated in randomized controlled trials specifically in patients with pfCD, its use has been explored in real-world prospective and retrospective studies. SC IFX treatment in patients with pfCD has achieved sustained clinical and radiological remission with low recurrence rates, and high treatment persistence was observed without new safety issues, supporting its potential as a therapeutic option for pfCD. SC IFX may provide additional advantages over IV IFX, including reduced treatment burden for patients. However, evidence from prospective studies specifically investigating SC IFX in pfCD remains limited. Further research, particularly studies evaluating pfCD-specific clinical and radiological outcomes, are needed to better define the role of SC IFX in pfCD treatment. In summary, this review underscores the well-established role of IV IFX in pfCD, highlights the emerging evidence supporting SC IFX, and identifies key knowledge gaps that require further investigation to inform future treatment strategies in pfCD.