Treatment trajectories and patterns following non-medical switching to biosimilar adalimumab in patients with hidradenitis suppurativa: a retrospective observational multicenter study from Saudi Arabia

Background Adalimumab is the first biologic approved for moderate-to-severe hidradenitis suppurativa (HS). Considering potential cost savings, real-world data evaluating the prescribing patterns following a switch from the originator in HS remain limited.Methods We conducted a retrospective multicenter observational study (2019–2025) at two hospitals in Saudi Arabia. Adult HS patients who received originator adalimumab for ≥3 months, and then switched to its biosimilar for non-medical reasons for ≥3 months were included. Descriptive statistics summarized baseline characteristics. A Wilcoxon paired test compared treatment durations, and a Sankey diagram illustrated treatment pathways.Results A total of 40 patients were included (median age: 26 years; 62.5% male; median BMI: 31.6). Most presented with nodules (55.0%), abscesses (47.5%), and sinus tracts (37.5%). Among all treatment actions/pathways, 22.6% represented treatment escalation to an alternative biologic, specifically secukinumab or ustekinumab. Patients who were switched from biosimilar therapy demonstrated more severe disease involvement. Median duration of originator therapy was 6.0 months versus 21.0 months for biosimilar (p = 0.477), with no significant difference in treatment persistence.Conclusion In this small real-world cohort, treatment escalation after switching to biosimilar adalimumab was observed in a subset of patients with more complex HS features. Larger studies using standardized severity measures are needed to confirm these observations.