Protagonist Therapeutics is a biopharmaceutical company that develops peptide-based therapeutic drugs for hematology and blood disorders, and inflammatory and immunomodulatory diseases. It is working on rusfertide, an injectable that mimics hepcidin to treat polycythemia vera and hereditary hemochromatosis, PN-943, an oral treatment for inflammatory bowel disease, and PN-235, an oral medication for IBD and other indications. Incorporated in 2006 and based in Newark, California, the company has a collaboration agreement with Janssen Biotech.