A Study of Guselkumab in Participants With Familial Adenomatous Polyposis

Inclusion Criteria: * Phenotypic familial adenomatous polyposis (FAP) with disease involvement of the colorectum by either genetic or clinical diagnosis: Adenomatous polyposis coli (APC) germline mutation with or without family history, or with greater than (\>)100 adenomas in large intestine and a family history of FAP, attenuated FAP is allowed. FAP phenotype post colectomy for polyposis with a family history of FAP may be allowed * Post-colectomy or subtotal colectomy * Polyps with a sum of diameters greater than or equal to (\>=)10 millimeter (mm) in the rectum or pouch on biopsy at screening * A woman of childbearing potential must agree not to get pregnant during the study and at least 12 weeks after the last dose of study administration * A woman must agree not to breast feed or donate eggs (ova, oocytes) during the study and for a period of 12 weeks after the last administration of study drug Exclusion Criteria: * Prior use of any biologic therapy targeting interleukin (IL)-12/23, IL-17, or IL-23 receptor * Use of non-steroidal anti-inflammatory drugs other than aspirin during the study. The use 100 milligram (mg) of aspirin a day or 700 mg of aspirin per week is allowed * Treatment with other FAP-directed drug therapy (including NSAID \[Nonsteroidal anti-inflammatory drug\] drugs), unless completes a 4-week washout period prior to randomization * High grade dysplasia or cancer on biopsy at screening in GI tract (including stomach, duodenum, and colon/rectum/pouch)…