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 81 milligram (mg) of aspirin a day or 650 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

- Duodenum or colon/rectum/pouch with high grade dysplasia or cancer on biopsy at
screening

- Duodenal or colorectal polyp >1 centimeter (cm) not excised at the screening
evaluation