Inflammatory bowel disease biologic therapy is one of the most heavily tested topics in the SCE Gastroenterology exam. The field moves quickly — new agents, biosimilars, and updated NICE technology appraisals change the landscape regularly. This page covers the key knowledge for exam preparation.
When to start biologics
Biologics are indicated for moderate-to-severe Crohn's disease or ulcerative colitis that has failed conventional therapy (5-ASAs for UC, corticosteroids, and immunomodulators — azathioprine, mercaptopurine, or methotrexate). The BSG and ECCO guidelines both recommend escalation to biologics when conventional therapy is insufficient, with the specific threshold depending on disease severity, extent, and phenotype.
NICE technology appraisals govern access in the UK. For Crohn's disease, NICE TA187 (infliximab and adalimumab) and subsequent TAs for vedolizumab, ustekinumab, and risankizumab set the eligibility criteria. For ulcerative colitis, the corresponding TAs apply to infliximab, adalimumab, golimumab, vedolizumab, tofacitinib, ustekinumab, and filgotinib.
The biologic classes
TNF inhibitors — infliximab, adalimumab, golimumab (UC only) — were the first biologic class and remain first-line biologic therapy for most patients. Infliximab is given intravenously (induction at weeks 0, 2, and 6, then maintenance every 8 weeks). Adalimumab is subcutaneous. Biosimilar availability has reduced costs substantially.
Anti-integrin therapy — vedolizumab — is gut-selective, blocking alpha-4-beta-7 integrin and preventing lymphocyte trafficking to the gut. Its gut selectivity gives it a favourable systemic safety profile compared to TNF inhibitors. Vedolizumab is positioned as either first-line biologic (particularly in UC where the evidence is strong) or second-line after TNF inhibitor failure.
Anti-IL-12/23 therapy — ustekinumab — targets the p40 subunit shared by IL-12 and IL-23. It is effective in both Crohn's disease and UC and is commonly used after TNF inhibitor failure. The induction dose is weight-based IV, followed by subcutaneous maintenance.
Anti-IL-23 therapy — risankizumab — targets the p19 subunit of IL-23 specifically. It is approved for Crohn's disease and represents the newest biologic class. Guselkumab and mirikizumab are in the same class with emerging evidence.
JAK inhibitors — tofacitinib (UC), filgotinib (UC), upadacitinib (Crohn's and UC) — are oral small molecules rather than biologics, but they occupy the same treatment space. They offer rapid onset and oral convenience but carry specific safety considerations (VTE risk, herpes zoster, cardiovascular events at higher doses).
Sequencing strategy
There is no single correct sequence — the choice depends on disease phenotype, severity, patient factors, and prior treatment history. However, the exam tests your ability to select the most appropriate next agent for a given clinical scenario.
For Crohn's disease, a typical sequence after conventional therapy failure is infliximab or adalimumab first-line, ustekinumab or vedolizumab second-line (after TNF failure), and risankizumab or upadacitinib third-line. For UC, infliximab or adalimumab first-line, vedolizumab or tofacitinib second-line, and ustekinumab or filgotinib third-line.
Therapeutic drug monitoring (TDM) is increasingly important. Measuring trough drug levels and anti-drug antibodies guides decisions about dose optimisation versus switching — a distinction the exam tests explicitly. Low trough levels with no antibodies suggest dose escalation. Low trough levels with antibodies suggest switching within class (if anti-TNF) or switching class.
What the exam tests
SCE questions on IBD biologics typically present a patient who has failed one or more therapies and ask you to choose the next step. The correct answer depends on which agents have been tried, the reason for failure (primary non-response versus secondary loss of response versus intolerance), and the NICE TA eligibility criteria. Ensure you know the NICE access criteria for each agent — the exam tests real-world prescribing decisions, not just pharmacology.
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