PURPOSE: The main purpose is to explore clinical efficacy and safety associated with capsule FMT (cFMT) performed in newly diagnosed, untreated patients with rheumatic and gastrointestinal chronic inflammatory diseases (CIDs).

DESIGN AND METHODS: In this 1:1 double-blind, placebo-controlled, randomised, 12-month exploratory trial, 200 patients with at least one of 6 different diagnoses of CIDs fulfilling the study criteria will be enrolled at time of diagnosis. The patient groups are: rheumatoid arthritis (RA), ankylosing spondylitis (AS), psoriatic arthritis (PsA), Crohn's disease (CD), and ulcerative colitis (UC). The primary endpoint is change from baseline to eight weeks in the physical component summary (PCS) of the short form health survey (SF-36). Key secondary clinical endpoints will be evaluated at 8 weeks. Other secondary clinical endpoints will be evaluated at 52 weeks and reported in secondary papers.

The baseline visit will be performed as quickly as possible after the patient's informed consent has been obtained to ensure no unnecessary treatment delay. Stratified by CID diagnosis, patients will be randomised (1:1) to either placebo or single-donor cFMT processed from stool provided to the hospital from anonymous-to-the-patient healthy donors. The experimental intervention FMT/placebo will be repeated once weekly the first month (i.e., each patient will receive a total of four treatments). In addition, all participants will concomitantly be offered the national guideline first-line anti-inflammatory treatment following the baseline visit.

At baseline, 8 weeks, 26 weeks, and 52 weeks a thorough clinical examination will be conducted and all relevant clinical scores for each disease entity will be registered. Patient-reported-outcomes including SF-36 and disease specific questionnaires will be collected at week 1, 2, 3, 4, 8 (primary endpoint evaluation), 26 and 52. Adverse events will be monitored through out the trial.

Inclusion criteria:

• Newly diagnosis of treatment-naïve RA, AS, PsA, PSar, CD, or UC.
• Treatment-naïve which is defined as no current or previous (within 3 months) disease-modifying anti-rheumatic drugs (DMARDs) or systemic anti-inflammatory treatment including glucocorticoids.
• Presence of CID treatment indication (no contra-indications) and patient accept to start first-line standard treatment in accordance with the national guideline for the specific diagnosis following the baseline visit.
• Age 18 to 75 years.

Exclusion criteria:

• Indication for biological therapy as primary therapy.
• Celiac disease or food allergy.
• Current cancer.
• Hepatitis B and C, HIV, HTLV1/2, and active TB or other serious chronic infections.
• Pregnant or breastfeeding women.
• Not wishing to participate or not suited for FMT intervention or project evaluation.

Data will be available upon reasonable request. This will require review and approval by the trial scientific board and the data responsible parties. Terms of collaboration will be reached together with a signed collaboration agreement and data processor agreement.