PERFUSE: a French non-interventional study of patients with inflammatory bowel disease receiving infliximab biosimilar SB2: a 12-month analysis

**Background:** Flixabi (SB2) is a biosimilar of reference infliximab (Remicade). While its approval was based on comparable efficacy and safety in rheumatoid arthritis, real-world evidence on long-term use in inflammatory bowel disease (IBD) – both in treatment-naive patients and those transitioning from prior infliximab – is limited. The PERFUSE study was designed to address this gap by evaluating persistence, effectiveness, immunogenicity, and safety of SB2 over 12 months in adults with Crohn's disease (CD) and ulcerative colitis (UC).

**Methods:** PERFUSE is a long-term, non-interventional, multicenter study conducted at 12 gastroenterology and 9 rheumatology sites across France. Patients aged ≥6 years with CD or UC who initiated SB2 from September 2017 were enrolled between June 2018 and July 2019. The analysis included 569 CD and 168 UC adult patients. Patients were categorized into four sub-cohorts based on prior infliximab exposure: IFX naive (no prior infliximab), prior IFX ref (reference infliximab), prior IFX bs (another infliximab biosimilar), and prior IFX multiswitch (both reference and biosimilar). The primary outcome was persistence on SB2 at Month 12, analyzed using Kaplan–Meier methods. Secondary outcomes included SB2 dose, disease activity (Harvey–Bradshaw Index for CD, Simple Clinical Colitis Activity Index for UC), immunogenicity (anti-drug antibodies via Lisa-Tracker ELISA), and safety (treatment-emergent adverse events). Data were collected from routine clinical visits at baseline, Month 6 (±2), and Month 12 (±2).

**Key Results:** Persistence on SB2 at Month 12 was high across all groups. For CD patients, persistence was 89.0% (95% CI: 77.2–94.9) in IFX naive, 94.0% (91.0–96.1) in prior IFX ref, 91.6% (86.0–95.0) in prior IFX bs, and 100% in prior IFX multiswitch. For UC patients, persistence was 78.5% (58.2–89.8) in IFX naive, 92.8% (84.8–96.7) in prior IFX ref, 94.2% (83.1–98.1) in prior IFX bs, and 100% in prior IFX multiswitch. Discontinuation rates were highest among IFX-naive UC patients (27%), with physician decision due to loss of response being the most common reason. SB2 doses remained stable over 12 months. Disease activity improved in IFX-naive patients: mean HBI change from baseline to Month 12 was −4.9 (95% CI: −7.7 to −2.1) in CD, and mean SCCAI change was −7.1 (95% CI: −9.6 to −4.7) in UC. Among patients with prior IFX, disease scores remained stable with minimal change (e.g., mean HBI change −0.3 [−0.7 to 0.0] for prior IFX ref CD). The proportion of IFX-naive CD patients in remission increased from 33% at baseline to 88% at Month 12; in UC, from 73% to 100%. Immunogenicity was low: among those with post-baseline testing, 6/30 CD and 5/16 UC IFX-naive patients had at least one positive anti-drug antibody test; in prior IFX groups, 32/330 CD and 9/92 UC patients had a positive result. No new safety signals were detected. Non-serious related TEAEs occurred in 7.3–16.5% of CD and 9.5–14.3% of UC patients across sub-cohorts. Serious related TEAEs were rare (7 patients, 9 events), including hypersensitivity, infections, and gastrointestinal disorders.

**Clinical Implications:** This real-world study demonstrates that SB2 is an effective and safe treatment option for IBD patients, whether used as a first-line infliximab or after switching from reference or other biosimilar infliximab. The high persistence rates (>90% in transitioned patients) suggest minimal nocebo effect, likely supported by patient education. The findings support the use of SB2 in routine practice, offering potential cost savings without compromising disease control or safety. Limitations include non-routine anti-drug antibody testing at some centers and lack of a control group continuing reference infliximab. Longer-term follow-up to 24 months is ongoing.