On this page
- What was actually tested
- What a fistula is, and why cells were tried
- How it is given, and why this matters enormously
- Evidence for treating the disease itself is much weaker
- Availability and regulation
- What the trials measured
- Who this applies to
- Risks
- Questions worth asking
- Frequently asked questions
- Requesting a medical evaluation
Cell-based approaches have been studied for complex perianal fistulas in Crohn’s disease. Earlier positive findings were not confirmed by a later large trial of darvadstrocel, and the evidence needs to be considered in that context.
What was actually tested
A phase III randomised double-blind trial tested expanded allogeneic adipose-derived cells in complex perianal fistulas — Expanded allogeneic adipose-derived mesenchymal stem cells (Cx601) for complex perianal fistulas in Crohn’s disease: a phase 3 randomised, double-blind controlled trial.
Long-term follow-up of that trial was published separately — Follow-up Study to Evaluate the Long-term Safety and Efficacy of Darvadstrocel (Mesenchymal Stem Cell Treatment) in Patients With Perianal Fistulizing Crohn’s Disease: ADMIRE-CD Phase 3 Randomized Controlled Trial.
A systematic review and meta-analysis pooled the perianal fistula literature — Mesenchymal stem-cell therapy for perianal fistulas in Crohn’s disease: a systematic review and meta-analysis.
The earlier trial and its follow-up are part of the evidence history. They must be assessed alongside the unsuccessful confirmatory study and subsequent EU withdrawal.
What a fistula is, and why cells were tried
A perianal fistula is an abnormal tunnel running from the bowel to the skin near the anus. It leaks, it becomes infected, and in Crohn’s disease it is notoriously hard to close.
Established options are drainage with a seton, antibiotics, biologic drugs, and surgery that carries a risk of continence problems. Many patients cycle through all of them.
Cells were tested here because it is a discrete target: a tract that can be found, cleaned and injected under anaesthetic, with an endpoint — closed or not closed — that is checked on examination and imaging rather than by asking the patient how they feel.
How it is given, and why this matters enormously
The procedure is performed under anaesthetic by a colorectal surgeon. The tract is curetted, internal openings are closed, and cells are injected into the tissue along the tract walls.
It is local, surgical, and targeted. It is not an intravenous infusion, and none of this evidence supports an infusion.
That distinction is the single most abused fact in this field. An infusion offered for Crohn’s disease on the strength of these trials is being sold on evidence that does not describe it.
Evidence for treating the disease itself is much weaker
A randomised controlled trial has tested cord-derived cells in Crohn’s disease more broadly — Umbilical Cord Mesenchymal Stem Cell Treatment for Crohn’s Disease: A Randomized Controlled Clinical Trial — and that is a single trial, not a phase III programme.
Treating the underlying inflammatory disease is a different target from closing a fistula: diffuse rather than local, measured by symptom and endoscopic scores rather than by whether a tract has sealed.
A meta-analysis of pharmacological options in fistulising Crohn’s places cell therapy alongside the drug treatments it competes with — Pharmacological Therapies for the Management of Fistulizing Crohn’s Disease: A Systematic Review and Meta-Analysis.
Availability and regulation
The product used in the phase III trials was a specific manufactured cell preparation with a defined dose, defined manufacturing and a previous EU authorisation that was withdrawn in December 2024.
A clinic offering cells for Crohn’s is not automatically offering that product, and the trials are specific to what was tested. Stem cell regulation in Thailand covers what is permitted here.
Ask directly whether the proposed treatment is the product studied, or a different preparation being offered on the strength of that product’s results.
What the trials measured
The primary endpoint in the phase III programme was combined remission: the fistula openings closed on examination, with no collection of fluid above a defined size confirmed on MRI.
That is a demanding definition and a checkable one. It does not rely on the patient reporting improvement, and it does not rely on the treating clinician’s impression. Imaging either shows a collection or it does not.
Contrast that with how results are presented in marketing, where “improvement” is rarely defined at all. The reason the Crohn’s fistula work is taken seriously is not that the results were spectacular — they were moderate — but that the question was asked in a way that could have returned a negative answer.
The long-term follow-up matters for the same reason. Closure at six months is a weaker claim than closure sustained over years, and the field’s willingness to publish the longer figure is a point in its favour.
Who this applies to
Patients with complex perianal fistulising Crohn’s disease, typically after other treatments have been tried, under the care of a colorectal surgeon and a gastroenterologist.
It does not apply to Crohn’s affecting the small bowel or colon without perianal disease, and it does not apply to ulcerative colitis — ulcerative colitis is graded separately and lower.
If you have Crohn’s without fistulising perianal disease, the local-injection studies do not describe your situation. The evidence for fistula treatment also remains uncertain after the confirmatory trial.
Risks
The procedural risks of an examination under anaesthetic and perianal surgery, including abscess formation.
Fistulas recur. Long-term follow-up reports outcomes over years rather than closure at a single timepoint, which is the more honest way to read it.
Ordinary risks of allogeneic cell administration. Adverse events covers what has been documented.
Questions worth asking
- Do I have complex perianal fistulising disease specifically?
- Is this the cell product studied in the phase III trials, or a different preparation?
- Is this a local injection under anaesthetic, or an infusion?
- Who is performing it, and are they a colorectal surgeon?
- What did the long-term follow-up show about recurrence?
The autoimmune overview places this against the rest of the group, and the evidence levels explain the grading.
Frequently asked questions
Do phase III trials establish that this treatment works?
No. Earlier positive results were not confirmed in ADMIRE-CD II, and Alofisel was withdrawn from the EU market. Ask your specialist to explain the complete evidence, not only the earlier studies.
Does that evidence support an infusion for Crohn’s?
No. The trials injected cells into and around a fistula tract under anaesthetic. An infusion is a different treatment entirely.
I have Crohn’s but no fistula. Does this apply?
Not really. One randomised trial exists for the disease more broadly, which is a much weaker basis than the fistula programme.
Will the fistula stay closed?
Fistulas recur. The long-term follow-up study reports outcomes over years, and that is the honest figure to ask for.
Is the cell product the same everywhere?
No. The trials used a specific manufactured preparation. A clinic offering cells is not automatically offering that product.
Can I stop my biologic drug?
That is a question for your gastroenterologist. Cell therapy here was studied as an addition for difficult fistulas, not as a replacement for disease control.
Requesting a medical evaluation
Nothing on this page establishes whether any treatment is appropriate for you. That needs your history, your imaging and your current medications read by a clinician. If you would like that review, send your records and we will tell you honestly whether there is anything worth discussing — including when the answer is no.
This page is general information, not medical advice, and does not create a doctor–patient relationship. Regenerative treatments discussed here are in most cases investigational. Discuss any treatment with a clinician who knows your history.