Sirolimus and Familial Adenomatous Polyposis (FAP)

Inclusion Criteria:

* ≥ 18 years
* A genetically confirmed APC mutation
* Classical FAP phenotype (100-1000 colorectal adenomatous polyps)
* Subtotal colectomy with ileorectal anastomosis (IRA) or total colectomy with ileo-anal pouch anastomosis (IPAA)
* Severe rectal or pouch polyposis, defined as having \>25 polyps amenable to complete removal (InSiGHT 2011 Staging System score of 3)
* Fertile patients must use effective contraception during study treatment and until 12 weeks after study treatment

Exclusion Criteria:

* Inability to give informed consent
* Participation in another interventional clinical trial
* Subjects who are pregnant or breast-feeding, proved with a negative pregnancy test if female of child-bearing potential
* Prior pelvic irradiation
* Invasive malignancy in the past 5 years
* Subjects who are HIV positive
* Subjects with severe systemic infections, current or within 2 weeks prior to study start
* Subjects with known severe restrictive or obstructive pulmonary disorders
* Known sucrase insufficiency, isomaltase insufficiency, fructose intolerance, glucose malabsorption, galactose malabsorption, galactose intolerance or Lapp-lactase deficiency
* History of pulmonary embolism or deep venous thrombosis
* Major surgery less than or equal to 2 weeks prior to enrollment or any planned surgery within treatment period
* Active post-operative complication, e.g. infection, delayed wound healing
* History of hypersensitivity to sirolimus or to drugs of similar chemical classes
* Regular NSAID use (defined as more than twice a week for 4 consecutive weeks) within 3 months prior to baseline
* Use of other FAP directed drug therapies (accepted if discontinued 3 months prior to start of the study)
* Subjects requiring systemic anticoagulation
* Co-medication that could interact with sirolimus
* Abnormal laboratory results (assessed within 14 days prior to start of study drug)