Study design: targeted, controlled, and clinically recognisable

The trial enrolled patients with active fistulising perianal Crohn’s disease and randomised them 1:1 to ustekinumab or placebo after standardised surgical management. The ustekinumab regimen consisted of 6 mg/kg intravenously at baseline, followed by 90 mg subcutaneously at week 8 and then every 8 weeks.

The study was multicentre and double-blind, conducted across 10 French centres under the Groupe d’Etudes Thérapeutiques des Affections Inflammatoires Digestives, or GETAID. Thirty-two patients were randomised: 16 to ustekinumab and 16 to placebo. The population was clinically challenging: 69% had prior anti-tumour necrosis factor failure.

This population detail is particularly important. A trial enriched with patients who have already failed anti-TNF therapy addresses a common real-world dilemma: what to do when first-line biologic strategies for fistulising perianal Crohn’s disease have not delivered adequate control. However, the same detail also affects interpretation. Outcomes in a previously anti-TNF-exposed population may not translate directly to biologic-naïve patients, and the small sample size limits confidence in subgroup-level conclusions.

The trial also included an open-label phase. At week 12, placebo non-responders could switch to ustekinumab, and ustekinumab non-responders could undergo treatment intensification during the open-label phase. This feature is clinically understandable, especially in a symptomatic fistulising disease population, but it complicates longer-term comparisons between the original randomised arms.

The week-12 signal: better combined remission with ustekinumab

At week 12, combined remission was achieved in 62% of patients receiving ustekinumab compared with 25% receiving placebo. The reported odds ratio was 5.1, with a 95% confidence interval of 1.07 to 24.4.

This is the central efficacy signal of the trial. The direction of effect favoured ustekinumab, and the outcome was clinically meaningful because it combined absence of drainage from external openings with MRI-based absence of abscesses larger than 2 cm. The finding suggests that ustekinumab may provide short-term benefit in active fistulising perianal Crohn’s disease after standardised surgical management.

The width of the confidence interval should be read carefully. A confidence interval from 1.07 to 24.4 reflects substantial uncertainty around the magnitude of effect, which is expected in a small trial with 32 randomised patients. The result supports a treatment signal but does not precisely define the size of benefit clinicians should expect in broader practice.

Clinical remission alone occurred in 62.5% of the ustekinumab group compared with 31% of the placebo group, with an odds ratio of 3.75 and a 95% confidence interval of 0.84 to 16.8. Radiological remission occurred in 87.5% versus 75%, with an odds ratio of 2.7 and a 95% confidence interval of 0.34 to 21.1.

These secondary outcomes are useful but should not be overinterpreted. The point estimates favour ustekinumab, but the confidence intervals are wide and include uncertainty. For practicing clinicians, the most defensible reading is that the composite week-12 endpoint provides the clearest positive signal, while the separate clinical and radiological components should be viewed as supportive but imprecise.

Why the composite endpoint is clinically meaningful

Perianal Crohn’s disease is not adequately captured by one measure. Drainage reflects the patient-facing and examination-facing burden of disease. MRI provides information about deeper inflammatory complications, particularly abscess. By combining both, the trial attempted to avoid the pitfall of mistaking external closure for complete disease control.

The radiological component used a pragmatic threshold: absence of abscesses larger than 2 cm on blinded central MRI. This does not necessarily mean complete anatomical healing of all fistula tracts. It means that, within the trial definition, radiological remission required absence of a clinically relevant abscess threshold. Clinicians should therefore avoid describing the primary endpoint as complete fistula healing unless they define exactly what was measured.

This distinction is more than semantic. Patients may ask whether a treatment “heals the fistula.” The trial supports a short-term improvement in a combined clinical and MRI-based endpoint, not a universal guarantee of durable fistula closure or elimination of future surgical need. The source details available do not justify claims about complete tract resolution, long-term prevention of recurrence, or superiority over other active biologics.

Interpreting the week-48 findings without overstating durability

The open-label phase provides additional context but less controlled evidence than the double-blind week-12 comparison. Nine placebo-group patients switched to ustekinumab during the open-label phase. Combined remission rates at week 48 were reported as 50% in the placebo arm and 31% in the ustekinumab arm.

These week-48 figures should be interpreted cautiously. Because non-responders could switch or intensify after week 12, the original randomised comparison becomes less straightforward. The lower week-48 combined remission rate in the original ustekinumab arm should not be read in isolation as evidence of loss of efficacy, nor should the 50% rate in the placebo arm be interpreted as placebo superiority. Treatment switching and intensification alter the meaning of arm-level comparisons.

The most reliable inference remains the short-term randomised comparison at week 12. The longer-term data raise important clinical questions about durability, optimisation, timing of intensification, and the role of ongoing surgical or imaging-based management, but they do not provide a clean placebo-controlled maintenance comparison.

What clinicians can reasonably conclude

The authors concluded that the findings suggest greater short-term clinical benefit with ustekinumab compared with placebo and support its use in patients with active fistulising perianal Crohn’s disease. That conclusion is appropriately measured. It does not claim that ustekinumab is curative, that it replaces surgical management, or that it should be considered definitively superior to other biologic strategies.

For gastroenterologists, the trial strengthens the evidence base for considering ustekinumab in active fistulising perianal Crohn’s disease, particularly in a population where many patients had prior anti-TNF failure. It also reinforces the importance of multidisciplinary management, because patients entered the trial after standardised surgical management. The medical therapy signal should therefore be understood as occurring within a structured care pathway rather than as isolated biologic treatment.

This is not evidence that ustekinumab should be used without adequate assessment for abscess, seton need, or surgical input. It is also not a direct comparison with anti-TNF therapy, vedolizumab, IL-23 inhibitors, antibiotics, stem-cell therapy, or surgical approaches. The trial compared ustekinumab with placebo under the trial protocol.

What clinicians should not conclude

Several conclusions would go beyond the source.

First, the trial does not establish ustekinumab as the best biologic for fistulising perianal Crohn’s disease. No active comparator was included. A placebo-controlled design answers whether ustekinumab performs better than placebo under study conditions; it does not rank ustekinumab against other treatments.

Second, the trial does not prove that ustekinumab prevents recurrence, avoids surgery, or reduces hospitalisation. Those outcomes are not supported by the source details available.

Third, the trial should not be presented as definitive for all patients with perianal Crohn’s disease. The sample was small, and most patients had prior anti-TNF failure. The findings may be most relevant to a specialist population with active draining disease managed in experienced centres.

Fourth, clinicians should not infer that week-48 arm-level results provide a simple maintenance efficacy estimate. The open-label crossover and intensification design makes those later outcomes clinically informative but methodologically less definitive than the week-12 endpoint.

Strengths that make the study clinically useful

Several features increase the value of the GETAID trial.

The study was randomised, double-blind, placebo-controlled, and multicentre. It focused specifically on active draining fistulising perianal Crohn’s disease rather than treating perianal disease as a small subgroup within a luminal Crohn’s trial. It used a clinically meaningful composite endpoint that incorporated both external drainage and blinded central MRI assessment for abscess. It also embedded treatment after standardised surgical management, reflecting the multidisciplinary reality of perianal Crohn’s care.

The inclusion of a high proportion of patients with prior anti-TNF failure is another clinically relevant feature. These are precisely the patients in whom clinicians often need additional evidence to support treatment selection.

Limitations that should shape practice interpretation

The most obvious limitation is size. Thirty-two randomised patients is a small trial, particularly for a heterogeneous condition such as fistulising perianal Crohn’s disease. Small trials can detect important signals, but they are vulnerable to imprecision. The wide confidence intervals around several outcomes reflect that uncertainty.

Second, the open-label phase limits clean interpretation of longer-term outcomes. Crossover and intensification are ethically and clinically understandable but reduce the ability to interpret week-48 arm comparisons as a sustained randomised treatment effect.

Third, the available source details do not provide enough information to make claims about specific fistula anatomy, quality of life, adverse event patterns, need for further procedures, or long-term recurrence. Those may be addressed in the full article, but they should not be invented or assumed from the abstract-level information.

Fourth, the trial’s findings apply to the studied intervention and protocol: intravenous induction followed by subcutaneous maintenance dosing after standardised surgical management. Extrapolation to different dosing strategies, earlier use, combination approaches, or non-specialist settings requires caution.

How this may influence future research

The GETAID trial strengthens the rationale for larger, phenotype-specific trials in perianal Crohn’s disease. Future studies should clarify durability, optimal timing of biologic initiation relative to surgical control, the value of dose intensification, predictors of response, MRI-based definitions of deeper healing, and patient-centred outcomes such as pain, drainage burden, continence concerns, work impairment, and quality of life.

The trial also highlights the need for standardised endpoints. A combined clinical-radiological endpoint may be more clinically meaningful than drainage alone, but future research should continue refining what constitutes true healing, meaningful improvement, and durable remission in fistulising disease.

Clinical Takeaway

The GETAID ustekinumab trial provides a focused, randomised placebo-controlled signal that ustekinumab improves short-term combined clinical and radiological remission in active fistulising perianal Crohn’s disease after standardised surgical management. The week-12 composite remission rate favoured ustekinumab, but the small sample size and wide confidence intervals mean the magnitude of benefit remains uncertain. Longer-term data are clinically interesting but harder to interpret because of open-label crossover and treatment intensification.

For clinicians, the study supports ustekinumab as an evidence-backed option in this difficult phenotype, especially when anti-TNF failure has occurred. It should not be framed as definitive proof of durable fistula healing, superiority over other therapies, or replacement for multidisciplinary surgical assessment. The most responsible interpretation is that ustekinumab now has placebo-controlled trial evidence suggesting short-term benefit in active fistulising perianal Crohn’s disease, while durability, optimisation, comparative positioning, and implementation remain important unanswered questions.

Five Key Clinical Takeaways

1. The GETAID trial was a double-blind, multicentre, randomised placebo-controlled trial of ustekinumab in active fistulising perianal Crohn’s disease.

2. Thirty-two patients were randomised across 10 French centres; 69% had prior anti-TNF failure, making the population clinically relevant but specialised.

3. At week 12, combined clinical and radiological remission occurred in 62% with ustekinumab versus 25% with placebo.

4. The primary endpoint combined absence of drainage from all external fistula openings with absence of abscesses larger than 2 cm on blinded central MRI.

5. The study supports a short-term treatment signal for ustekinumab, but small sample size, wide confidence intervals, and open-label crossover limit conclusions about durability and comparative positioning.

Source Reference and Link

Wils P, Nancey S, Messmer E, et al.; Groupe d'Etude Thérapeutique des Affections Inflammatoires du Tube Digestif (GETAID). Ustekinumab for fistulising perianal Crohn’s disease: a randomised placebo-controlled trial from the GETAID. Gut. Published online July 24, 2026. DOI: 10.1136/gutjnl-2026-339158. Trial registration: NCT04496063.