Callisto Pharmaceuticals, Inc., a development stage biopharmaceutical company, focuses on the development of drugs to treat gastrointestinal (GI) disorders and diseases. The company s lead drug candidates comprise Plecanatide, a guanylyl cyclase C (GC-C) receptor agonist, to treat GI disorders, primarily chronic constipation and constipation-predominant irritable bowel syndrome; and SP-333, a second generation GC-C receptor agonist, which is in pre-clinical development to treat gastrointestinal inflammatory diseases. It develops plecanatide, which under Phase II/III clinical trials and is intended for the treatment of chronic idiopathic constipation. The company was founded in 1996 and is headquartered in New York, New York.