Protagonist Therapeutics, Inc. operates as a discovery and development company in the United States. It develops Icotyde, a first-in-class investigational targeted oral peptide for the treatment of adults and pediatric patients 12 years of age and older with moderate-to-severe plaque psoriasis; and Rusfertide, a first-in-class investigational injectable mimetic of the natural hormone hepcidin in Phase 3 development for the treatment of the rare blood disorder polycythemia vera.