Protagonist Therapeutics, Inc. Common Stock, also called Protagonist Therapeutics, is a clinical-stage biopharmaceutical company, which engages in the research and development of novel constrained peptide-based drug candidates that address significant unmet medical needs. Read More The firm's initial lead product candidates, PTG-100 and PTG-200, are being developed for moderate-to-severe ulcerative colitis and Crohn's disease, respectively. The company was founded by Mark L. Smythe on August 22, 2006 and is headquartered in Newark, CA.