Organization and Description of Business	3 Months Ended
Mar. 31, 2026
Organization and Description of Business
Organization and Description of Business	Note 1.Organization and Description of Business Protagonist Therapeutics, Inc. (the “Company”) is a discovery through late-stage development biopharmaceutical company with a proprietary peptide technology platform that enables de novo discovery of peptide therapeutics. The Company’s programs fall into three broad therapeutic areas: (i) inflammation and immunology (“I&I”), (ii) hematology and (iii) metabolic diseases. The Company’s aim is to develop medicines for biologically and commercially validated targets which demonstrate a strong differentiation compared to existing therapies. ICOTYDE™ (icotrokinra) was approved in the United States in March 2026 for the treatment of moderate-to-severe plaque psoriasis in adults and pediatric patients 12 years of age or older who weigh at least 40kg and are candidates for systemic therapy or phototherapy. ICOTYDE is the first and only targeted oral peptide that precisely blocks the Interleukin-23 receptor (“IL-23R”) and is licensed to Janssen Biotech, Inc, a Johnson & Johnson company (“JNJ”). ICOTYDE was jointly discovered by the Company and JNJ scientists, with the Company having primary responsibility for the development of ICOTYDE through Phase 1, and JNJ assuming responsibility for further development and commercialization. In September 2025, JNJ submitted an application to the European Medicines Agency (“EMA”) seeking the first approval of ICOTYDE for the treatment of adults and pediatric patients 12 years of age and older with moderate-to-severe plaque psoriasis. ICOTYDE is in Phase 3 development for psoriatic arthritis and ulcerative colitis, and in Phase 2b/3 for Crohn’s disease. Rusfertide, a first-in-class investigational injectable mimetic of the natural hormone hepcidin, is currently in development for the treatment of the rare blood disorder polycythemia vera (“PV”). Rusfertide is being co-developed with Takeda Pharmaceuticals, Inc. (“Takeda”). The Company holds an option to co-commercialize rusfertide in the United States through a 50/50 profit and loss share structure with Takeda or can opt out of this structure. In August 2025, rusfertide was granted Breakthrough Therapy designation by the U.S. Food and Drug Administration (the “FDA”) for the treatment of erythrocytosis in patients with PV. In December 2025, a New Drug Application (“NDA”) was submitted to the FDA by Takeda and the Company seeking the first approval of rusfertide for the treatment of adults with PV. The NDA was granted priority review by the FDA, with a Prescription Drug User Fee Act target action date in the third quarter of 2026. The Company also has a number of clinical and pre-clinical programs addressing biologically and commercially validated targets, including IL-17 oral peptide antagonist PN-881, obesity triple agonist peptide PN-477, obesity dual agonist peptide PN-458, oral small molecule hepcidin functional mimetic PN-8047, and IL-4 and amylin programs. The Company is headquartered in Newark, California and has one wholly owned subsidiary, Protagonist Pty Limited (“Protagonist Australia”), located in Brisbane, Queensland, Australia.

Organization and Description of Business

3 Months Ended

Mar. 31, 2026

Organization and Description of Business

Organization and Description of Business

Note 1.Organization and Description of Business

Protagonist Therapeutics, Inc. (the “Company”) is a discovery through late-stage development biopharmaceutical company with a proprietary peptide technology platform that enables de novo discovery of peptide therapeutics. The Company’s programs fall into three broad therapeutic areas: (i) inflammation and immunology (“I&I”), (ii) hematology and (iii) metabolic diseases. The Company’s aim is to develop medicines for biologically and commercially validated targets which demonstrate a strong differentiation compared to existing therapies.

ICOTYDE™ (icotrokinra) was approved in the United States in March 2026 for the treatment of moderate-to-severe plaque psoriasis in adults and pediatric patients 12 years of age or older who weigh at least 40kg and are candidates for systemic therapy or phototherapy. ICOTYDE is the first and only targeted oral peptide that precisely blocks the Interleukin-23 receptor (“IL-23R”) and is licensed to Janssen Biotech, Inc, a Johnson & Johnson company (“JNJ”). ICOTYDE was jointly discovered by the Company and JNJ scientists, with the Company having primary responsibility for the development of ICOTYDE through Phase 1, and JNJ assuming responsibility for further development and commercialization. In September 2025, JNJ submitted an application to the European Medicines Agency (“EMA”) seeking the first approval of ICOTYDE for the treatment of adults and pediatric patients 12 years of age and older with moderate-to-severe plaque psoriasis. ICOTYDE is in Phase 3 development for psoriatic arthritis and ulcerative colitis, and in Phase 2b/3 for Crohn’s disease.

Rusfertide, a first-in-class investigational injectable mimetic of the natural hormone hepcidin, is currently in development for the treatment of the rare blood disorder polycythemia vera (“PV”). Rusfertide is being co-developed with Takeda Pharmaceuticals, Inc. (“Takeda”). The Company holds an option to co-commercialize rusfertide in the United States through a 50/50 profit and loss share structure with Takeda or can opt out of this structure. In August 2025, rusfertide was granted Breakthrough Therapy designation by the U.S. Food and Drug Administration (the “FDA”) for the treatment of erythrocytosis in patients with PV. In December 2025, a New Drug Application (“NDA”) was submitted to the FDA by Takeda and the Company seeking the first approval of rusfertide for the treatment of adults with PV. The NDA was granted priority review by the FDA, with a Prescription Drug User Fee Act target action date in the third quarter of 2026.

The Company also has a number of clinical and pre-clinical programs addressing biologically and commercially validated targets, including IL-17 oral peptide antagonist PN-881, obesity triple agonist peptide PN-477, obesity dual agonist peptide PN-458, oral small molecule hepcidin functional mimetic PN-8047, and IL-4 and amylin programs.

The Company is headquartered in Newark, California and has one wholly owned subsidiary, Protagonist Pty Limited (“Protagonist Australia”), located in Brisbane, Queensland, Australia.