<prompt> Linaclotide is aChloride channel activatorCFTR blockerSomatostatin antagonistGuanylate cyclase agonist  <response>: Linaclotide is a Guanylate cyclase - C agonist that increases levels of cGMP and stimulates secretion of chloride bicarbonate ions into the intestinal lumen. It is used in treatment of IBS with constipation. 