Histologically confirmed cutaneous melanoma classified as irresectable stage III or stage IV disease
Measurable disease according to RECIST 1.1 criteria
Age ≥ 18 years
Starting standard-of-care treatment with ICI in first line
Written informed consent must be given
Able to read and understand Dutch or English
Able to comply with study procedures (e.g. willing to provide fecal samples)
You may not be if
Symptomatic brain metastases
Received prior immunotherapy; previous (neo)adjuvant treatment is allowed if the last administration is at least 6 months ago
Use of systemic immunosuppressive medications
Use of laxatives up to 1 week prior to start of ICI
Use of supplements that alter bowel function or gut microbiota such as fibers/prebiotics, probiotics, synbiotics, or postbiotics up to 1 month prior to start of ICI
Use of antibiotics up to 1 months prior to start of ICI
Use of proton pumps inhibitors (PPI's) up to 3 months prior to start of ICI
Pregnant or lactating
Current participation in another clinical trial requiring the use of study medication
Has a known allergy to plants such as lettuce, sage, tarragon, chicory, artichoke, chamomile, daisy, or sunflower.
Has a medical history of gastrointestinal resection (appendectomy is allowed)
