Background There are no head-to-head randomised controlled trials (RCTs) comparing the effectiveness of biologics in ulcerative colitis (UC). We aimed to assess the cost-effectiveness of adalimumab, infliximab and vedolizumab as first-line agents to induce clinical remission and mucosal healing (MH) in UC.

Methods We constructed a decision tree based on a payer's perspective in the USA to estimate the first year costs of adalimumab, infliximab or vedolizumab to achieve clinical remission and MH in patients with moderate-to-severe UC. Transition probabilities were derived from ACT, ULTRA and GEMINI RCT data. Costs were derived from Medicare reimbursement rates and wholesale drug prices.

Results Assuming a biological-naïve cohort, infliximab 5 mg/kg every 8 weeks was more cost-effective ($99 171 per MH achieved) than adalimumab 40 mg every other week ($316 378 per MH achieved) and vedolizumab every 8 weeks ($301 969 per MH achieved) at 1 year. Non-drug administration cost of infliximab exceeding $1974 per infusion would make adalimumab more cost-effective. First-line UC therapy with vedolizumab would be cost-effective if the drug acquisition price was <$2537 for each 300 mg administration during the 1-year time horizon.

Conclusions If non-drug costs of infliximab administration are not excessive (<$2000), infliximab is the most cost-effective first-line biologic for moderate-to-severe UC. Exceeding this threshold infusion-related cost would make adalimumab the more cost-effective therapy. Considering its drug costs in the USA, vedolizumab appears to be appropriately used as a second-line biologic after antitumour necrosis factor failure.