Linaclotide Acetate in Preventing Colorectal Cancer in Healthy Volunteers

PRIMARY OBJECTIVES: I. To assess the pharmacodynamic effect (PD) of linaclotide (linaclotide acetate) (single daily dose x 7 days, stage I cohort dose= 0.870 mg/day) on cyclic guanosine monophosphate (cGMP) levels, based on biopsy samples obtained pre- and post-intervention from the rectum, until an effect is documented. SECONDARY OBJECTIVES: I. To confirm the safety and tolerability of linaclotide. II. To assess the pharmacodynamic effect of linaclotide on cGMP levels, analyzed sequentially from the transverse colon to the cecum, if no cGMP effect was observed in the rectum for the primary endpoint. III. To compare the change in the cGMP levels from baseline to day 7 between all the assigned doses of linaclotide (including placebo), analyzed sequentially from the rectum, transverse colon, and cecum. IV. If the study proceeds to stage II, the pharmacodynamic effect of linaclotide on cGMP levels will be assessed from day 6 rectal biopsies (un-prepped). TERTIARY OBJECTIVES: I. To assess the pharmacodynamic effect of linaclotide on an additional pathway-specific biomarkers relevant to guanylate cyclase C (GCC) signaling (i.e., vasodilator-stimulated phosphoprotein \[VASP\] phosphorylation) and a marker of general proliferation (Ki67 expression), based on intestinal mucosa biopsy samples obtained by colonoscopy pre- and post-exposure at the anatomical location (rectum, transverse colon, or cecum) in which cGMP is elevated following linaclotide exposure. OUTLINE: This is a dose-escalation study. Participants are randomized to 1 of 2 treatment arms. ARM I: Participants receive linaclotide acetate orally (PO) once daily (QD) on days 1-7. ARM II: Participants receive placebo PO QD on days 1-7. After completion of treatment, participants are followed up for 21-51 days.