S1062 Real-World Outcomes of a Mandatory Adalimumab Non-Medical Biosimilar Switch for Patients With Inflammatory Bowel Disease: A Single Center Retrospective Study

Introduction: Adalimumab (ADA) is a tumor necrosis factor alpha (TNF-α) antagonist that is approved for the treatment of inflammatory bowel disease (IBD) in Canada. Between April to September 2021, the province of British Columbia implemented a mandatory non-medical switch of Humira to 1 of 5 approved biosimilars. While existing evidence supports the safety and efficacy of biosimilars, data regarding non-medical switching of ADA in IBD patients remain sparse. Methods: A retrospective observational study was conducted using a patient database from IBD Centre of BC, a tertiary referral centre associated with St. Paul’s Hospital in British Columbia, Canada. The disease outcomes of patients on Humira who switched to 1 of the 5 ADA biosimilars were compared to patients who remained on Humira through compassionate support or private pay. The primary outcome was treatment persistence at 30 months post-switch assessed by Kaplan-Meier survival analysis. Secondary outcomes included frequency of reasons for ADA discontinuation, loss of response rates, adverse events, as well as clinical and biochemical remission status. Patients who were initiated directly on a biosimilar were excluded. Results: Patients in the originator (n=43) and biosimilar (n=228) groups displayed similar demographics and baseline disease characteristics. By the study endpoint of 30 months, there was no difference in the rate of treatment persistence in either group (n=36, 83.7% originators vs n= 201, 88.2% biosimilars, P =0.45). Treatment persistence assessed by Kaplan survival analysis demonstrated similar rates of discontinuation between both study groups (log-rank P-value = 0.537). There was a numerical but not statistically significant difference in rates of adverse events between either group (39.5 originator vs 28.9% biosimilars, P =0.206). This included comparable rates of loss of response (27.9 vs 17.5%) or adverse events (11.6 vs 11.4%) between the originator and biosimilar cohorts. C-reactive protein and fecal calprotectin levels were also similar 1 year pre- and post-switch. Conclusion: Non-medical switching of the ADA originator to 1 of 5 biosimilars did not result in differences in treatment persistence or adverse outcomes compared to originator molecule continuation for patients with IBD. These data will help inform patients and physicians in jurisdictions currently undergoing biosimilar switching (see Figure 1, Table 1).Figure 1.: Kaplan-Meier survival analysis does not demonstrate any statistically significant difference in treatment persistence by 30-months of patients who remain on the originator vs those who underwent the biosimilar switch (log-rank P = 0.543). Seven discontinuations (16.3%) occurred in the originator group, compared to 27 (11.8%) in the biosimilars group. Specific reasons for treatment discontinuations are summarized in Table 1. Table 1. - Baseline Characteristics Adalimumab Originator Adalimumab Biosimilar Switch P-value test N 43 228 Gender (M) 20 (45.4) 128 (56.3) 0.249 Fisher’s Exact Age at switch (years) 46.1 ± 15.3 40.6 ± 14.9 < 0.001 Mann-Whitney U Test Smoking 6 (14.0) 19 (8.30) 0.264 Fisher’s Exact Age at IBD diagnosis (years) 32.1 ± 15.7 26.3 ± 12.7 0.135 Mann-Whitney U Test Crohn’s Disease 35 (88.3) 192 (84.2) 0.654 Fisher’s Exact Age at diagnosis Fisher’s Exact A1 (< 16) 4 (11.4) 47 (20.6) 0.122 A2 (17-40) 20 (57.1) 120 (52.6) 0.574 A3 ( >40) 11 (31.4) 26 (10.9) 0.011 Location Fisher’s Exact L1 (Ileal) 12 (34.3) 69 (35.9) 1 L2 (Colonic) 8 (22.9) 41 (21.5) 0.825 L3 (Ileocolonic) 15 (42.9) 78 (40.6) 0.853 L4 (Isolated upper tract disease) 1 (2.86) 1 (0.52) 0.285 Behaviour Fisher’s Exact B1 (non-stricturing, non-penetrating) 10 (28.6) 70 (36.4) 0.444 B2 (stricturing) 11 (31.4) 53 (27.6) 0.684 B3 (penetrating) 2 (5.71) 38 (19.8) 0.052 Perianal Disease Modifier 11 (31.4) 65 (33.9) 0.847 Fisher’s Exact UC 8 (17.0) 36 (15.7) Fisher’s Exact E1 (ulcerative proctitis) 1 (12.5) 1 (2.78) 0.334 E2 (Left-sided colitis) 1 (12.5) 9 (25.0) 0.659 E3 (Extensive colitis) 6 (75.0) 26 (72.2) 1 Extra-intestinal manifestations 12 (27.9) Skin 3 (6.98) 27 (11.8) 0.437 Joint 6 (14.0) 38 (16.7) 0.823 Eye 4 (9.30) 10 (4.38) 0.249 PSC 0 1 (0.44) 1 Concurrent immunomodulatortherapy (azathioprine/methotrexate) 4 (6.98) 39 (17.1) 0.258 Fisher’s Exact Concurrent corticosteroid use 3 (6.98) 11 (3.95) 0.473 Fisher’s Exact Duration on adalimumab prior to switch (months) 89.5 ± 206.0 64.5 ± 40.3 0.719 Mann-Whitney U Test Pre-switch CRP (mg/L) 2.21 ± 1.99 6.46 ± 22.0 0.359 Paired t-test Pre-switch FCP (mcg/g) 215.6 ± 279.7 203.8 ± 413.6 0.972 Paired t-test UC – ulcerative colitis.PSC – primary sclerosing cholangitis.CRP – c-reactive protein.FCP – fecal calprotectin.Both biosimilar and originator cohorts display similar baseline patient demographics and pre-switch disease activity.

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