Introduction:
     
     Vedolizumab is a gut-selective anti-lymphocyte trafficking biologic indicated for the treatment of adult patients with moderately to severely active ulcerative colitis (UC) and Crohn's disease (CD) in Canada.
   

Objective:
     
     The objective of this study was to evaluate the cost effectiveness of treatment sequencing for UC and CD from a public healthcare payer perspective, leveraging new real-world evidence from the literature and the EVOLVE study, a retrospective chart review.
   

Methods:
     
     Using separate decision tree/Markov models to assess cost effectiveness for UC and CD, two sequencing approaches were estimated for adult patients (≥ 18 years) diagnosed with UC or CD who were biologic-naïve: vedolizumab as first-line biologic followed by anti-tumor necrosis factor (TNF)-α versus first-line anti-TNFα followed by vedolizumab. Treatment effectiveness (response and remission), surgery rates, dose escalation and regain of response and safety inputs were estimated from EVOLVE, a retrospective chart review of real-world data, and evidence synthesis from the literature, whereas costs and utilities were estimated from health technology assessment reports, clinical trials, and the literature. Biosimilar costs were used for anti-TNFα. Both models simulated a 5-year time horizon and discounted costs and outcomes at 1.5%. Probabilistic base-case analyses (n = 10,000) reported total costs (2023 Canadian dollars) and quality-adjusted life-years (QALYs). Several scenario analyses were conducted to explore robustness of results.
   

Results:
     
     In UC, vedolizumab as a first-line biologic followed by anti-TNFα resulted in an incremental gain of 0.09 QALYs (2.46 vs. 2.55) and saved $7179 ($134,028 vs. $126,848), making this a dominant strategy compared with first-line anti-TNFα followed by vedolizumab. In CD, use of vedolizumab as a first-line biologic resulted in an incremental gain of 0.04 QALYs (3.35 vs. 3.39) at an incremental cost of $50,631 ($89,850 vs. $140,381) versus first-line anti-TNFα followed by vedolizumab (incremental cost-effectiveness ratio of $1,265,775 per QALY).
   

Conclusions:
     
     Based on this analysis, sequencing vedolizumab as a first-line biologic prior to anti-TNFα in UC and CD provided additional clinical benefit to patients. In UC, vedolizumab as a first-line biologic also saved healthcare system costs compared with anti-TNFα, whereas in CD, vedolizumab provided incremental benefit at an incremental cost, which was not considered cost effective at a threshold of $50,000/QALY.