Sirolimus and Familial Adenomatous Polyposis (FAP)

Participants will be given sirolimus tablets. The starting dose is 2 mg once daily which will be given in 1mg tablets. On day 7 the first trough level is measured (using the LC-MS/MS method) and if not within the target range of 5-8ng/ml, dosing adjustments are made. In case of dosing adjustments, the next trough level is measured seven days later and this is repeated weekly until the target range is achieved. In case trough levels are within the target range, the next trough level measurement is at month 3, after which dosing adjustments are made if necessary, and at month 6. The maximum daily dose is 40mg. No placebo is given.