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5 Reasons for Participating in the Study Programme

The YELLOWSTONE Study Programme aims to determine how well the investigational drug works and how tolerable it is. Participation offers opportunities for those affected.


5 Reasons for Participating in the Study Programme

The YELLOWSTONE Study Programme aims to determine how well the investigational drug works and how tolerable it is. Participation offers opportunities for those affected.

The investigational medicine may reduce disease activity and your Crohn's disease symptoms, thus potentially improving your quality of life.


You are medically closely monitored and accompanied by doctors, nursing, and study staff.


The investigational medicine or the placebo, a sham drug without an active ingredient, is swallowed as a capsule.


By participating in the study programme, you support medical research on Crohn's disease.


After the induction or maintenance study, you can continue to receive the investigational drug as part of a subsequent extension study.

Possible Risks

As with all clinical trials, participating may involve potential risks. The investigational medicine may not work or not work as desired, or unexpected events may occur. For this reason, you will be monitored closely. In addition, you may not receive the investigational drug itself, but only a placebo, i.e. a sham drug without an active substance. Therefore, you will be given detailed information by a study doctor before you start taking part in the study. The probability that you will receive the placebo in the induction study is 33 per cent. If your symptoms do not improve during the induction study, there is always the possibility that you will enter the extension study, in which each study participant will receive the investigational medicine “unblinded”.


What Is the YELLOWSTONE Study Programme?

The YELLOWSTONE Study Programme comprises three clinical studies: an entry study (also called an induction study), a maintenance study, and an open-label extension study. Patients who want to take part in the YELLOWSTONE Study Programme first start with the induction study. Depending on your clinical improvement, you decide with the investigator whether you wish to continue participating in the study programme. You can also drop out at any time. You can find out more here. The YELLOWSTONE Study Programme at a glance:


The Mechanism of Action at a Glance

Crohn’s disease is a chronic inflammatory bowel disease in which the immune system overreacts. The associated immune reactions then lead to inflammatory changes in the gastrointestinal tract typical of Crohn’s disease. The investigational drug has a novel mechanism of action. It reduces the excessive activity of the immune system. In this way, harmful inflammatory reactions should be minimised.

Processes in Crohn's disease

The immune system in the gut is out of balance and overreacts. Various immune cells of the immune system play a role in this, especially T cells. In Crohn’s disease, T cells migrate increasingly into the intestinal mucosa. This aggravates inflammation, and over time the typical inflammatory sites of Crohn’s disease develop.

Mechanism of action of the investigational drug1,2

The investigational medicine decreases immune cell migration (especially T cells) from the lymphatic tissue into the bloodstream. This reduces the number of these cells in the blood, which probably results in fewer cells migrating into the gut. The inflammation in the gut is thus presumably improved.


This Is How the Induction Study Works

Inform yourself & check eligibility
You will find the most important information about the YELLOWSTONE Study Programme on this website. Take your time to read through everything. Then you can use the non-binding questionnaire to check whether you meet the most important criteria for participation in the study and are generally eligible to take part.
Initial informative consultation
At the end of the questionnaire, you can leave us your contact details. Our Patient Information Service will then contact you personally in a non-binding telephone call. We will clarify the next steps with you and provide you with the contact details of the nearest study site. You can then make an appointment with the study site.
Visit to the study site
At your first appointment at the study site, you will meet the study doctor. They will explain the details of the study to you in detail and check once again whether you are eligible to take part in the induction study. You will receive all the information in writing and can read it when you have time. Only after your appointment will you decide together with your attending doctor whether you want to take part. Once you have understood everything and decided to participate, you and your study doctor can sign the consent form.
Study start & preliminary examination
With your written consent, the induction study begins – initially as a preliminary examination phase: your study doctor will carry out a series of examinations and record your medical history and medication intake to determine whether you also meet the medical requirements to take part in the study. You will also undergo a colonoscopy. Generally, these examinations are completed within about half a day. If the results of the preliminary examination confirm your eligibility, your study doctor will finally admit you to the induction study.
Treatment phase
In the following twelve weeks, you will be asked to come to the study site for a further four visits. On day 1, you will receive the investigational drug for the first time (either the medication or the placebo, if applicable), which you will swallow as a capsule. Then, during the first seven days, the dose of the investigational drug will be gradually increased up to the target dose – or you will receive the placebo.

Approximate time spent at the study site:

  • Day 1 visit
    Duration ≈2-3 hours; if a long-term ECG is required, then 7-8 hours

  • Week 4 visit
    Duration ≈2 hours

  • Week 8 visit
    Duration ≈2 hours

  • Week 12 visit
    Duration ≈3 hours

Conclusion & follow-up
After the 12-week treatment phase, you will check with your study doctor whether you want to continue participating in the study programme or whether you would like to end your participation. If you are not interested in continuing in the YELLOWSTONE Study Programme, two further visits at 30 and 90 days are required for follow-up.
Subsequent studies
At your visit in week 12, the study doctor will assess your disease activity. If your disease has improved significantly in the induction study, you have the option of taking part in the subsequent maintenance study. The purpose of this study is to see whether the treatment effects continue or even improve. This study is also placebo-controlled. This means that you may also receive a placebo. If your disease has not improved enough after the end of the induction study, you can switch to an open-label extension study, in which you will always receive the investigational drug containing the active substance. A separate declaration of consent is necessary for participation in either of these two studies.


Are You Eligible for the Induction Study?

The YELLOWSTONE induction study is aimed at adults with moderate to severe Crohn’s disease.

You may be eligible to participate in the induction study if:


You are between 18 and 75 years old.


A doctor has diagnosed you with Crohn's disease.

You have already received at least one medication against Crohn's disease, and it has not led to a sustained improvement, or you have had to discontinue it due to side effects.


You have to go to the toilet more than three times a day, and your stool has a watery or mushy consistency.


You have a disease activity score CDAI (Crohn's Disease Activity Index) between 220 and 450.


You are not pregnant, are not breastfeeding and are willing to use contraception.

Participation in the induction study is not possible if, for example, the following applies:


You have another chronic inflammatory bowel disease such as ulcerative colitis.


You have a surgical procedure on the gastrointestinal tract within the next three months.


You cannot have a colonoscopy.


You have type 1 diabetes or untreated type 2 diabetes.


You have had cancer (except basal cell or squamous cell skin cancer) within the last five years.

You have already been treated with four different biologics.


Location of the YELLOWSTONE Study Programme







Are you interested in the YELLOWSTONE Study Programme?

Find out now, without obligation, via our questionnaire whether you are eligible for study participation.

  • Danese S, et al. J Crohns Colitis. 2018;12:S678-S686.
  • Approval of Zeposia in Switzerland, (last accessed June 2021)