An Investigational Drug (TPST-1495) in Patients With Familial Adenomatous Polyposis

Inclusion Criteria: * Diagnosis of familial adenomatous polyposis (FAP), defined as at least one of the following: * Genetic diagnosis with confirmed APC mutation (clinical CLIA \[clinical laboratory improvement amendments\] certified lab or research testing) * Obligate carrier * Clinical diagnosis of classic FAP with ≥ 100 colorectal adenomas status post colectomy or a sub-total colectomy and a family history of FAP * Clinical diagnosis of FAP, based on personal and family history. Note: This criterion requires documented review and agreement from either the study chair or the MW consortium lead investigator * Previously underwent prophylactic colectomy or sub-total colectomy with IRA (ileo-rectal or ileo-colonic anastomosis) or IPAA at least 12 months before pre-registration evaluation and without ongoing surgical complication * Willing to discontinue taking non-steroidal anti-inflammatory drugs (NSAIDs) 5 days prior to initiation of study treatment and limit frequency of NSAID dosing during study treatment * Age ≥ 18. Because no dosing or adverse event (AE) data are currently available on the use of TPST-1495 in participants \< 18 years of age, children and adolescents are excluded from this study but will be eligible for future pediatric trials, if applicable * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 (Karnofsky ≥ 60%) * Leukocytes (white blood count \[WBC\]) ≥ 3,000/uL (≥ 2,500/uL for African American participants) * Platelet count ≥ 100…