Business Description

OVERVIEW Protagonist Therapeutics, Inc. (referred to as “Protagonist,” the “Company,” “we,” “our” or “us”) is an integrated discovery and development company with a validated technology platform. Our programs fall into three broad therapeutic areas: (i) inflammation and immunology (“I&I”), (ii) hematology and (iii) metabolic diseases. Our aim is to develop medicines for biologically and commercially validated targets which demonstrate a strong differentiation compared to existing therapies. Our Development Products and Discovery Programs Icotyde™ (icotrokinra) Icotyde™ (icotrokinra) is a first-in-class investigational targeted oral peptide that selectively blocks the Interleukin-23 receptor (“IL-23R”), which underpins the inflammatory response in psoriasis and offers potential in other IL-23-mediated diseases. Icotyde is licensed to Janssen Biotech, Inc., a Johnson & Johnson company (“JNJ”), under a license and collaboration agreement initially entered into in 2017. Following Icotyde’s joint discovery by Protagonist and JNJ scientists, pursuant to the license and collaboration agreement, we were primarily responsible for the development of Icotyde through Phase 1, with JNJ assuming responsibility for development in Phase 2 and beyond. In July 2025 and September 2025, respectively, JNJ submitted a New Drug Application (“NDA”) to the U.S. Food and Drug Administration (“FDA”) and 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. JNJ has disclosed that it expects to launch Icotyde in the United States in 2026, subject to regulatory approval. Rusfertide Rusfertide is a first-in-class investigational injectable mimetic of the natural hormone hepcidin in development for the treatment of the rare blood disorder polycythemia vera (“PV”). We discovered rusfertide, advanced it into Phase 3 development, and in early 2024 entered into a co-development and co-commercialization arrangement with Takeda Pharmaceuticals, Inc. (“Takeda”) under a license and collaboration agreement entered into in January 2024. We 4 Table of Contents remained primarily responsible for clinical development activities through rusfertide’s NDA filing for the treatment of erythrocytosis in patients with PV, which we and Takeda submitted in December 2025. Rusfertide has also received Orphan Drug status, Fast Track designation and, in August 2025, Breakthrough Therapy designation (“BTD”). BTD is a process designed to expedite the development and review of drugs that are intended to treat a serious condition, and preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over available therapies. BTD also provides eligibility for priority NDA review, and Orphan Drug status qualifies sponsors for various incentives, including the potential for extended market exclusivity. Takeda has disclosed that it expects to launch rusfertide in the second half of 2026, subject to regulatory approval. IL-17 Program PN-881 . We are developing PN-881, a potential best-in-class oral peptide IL-17 antagonist, for the treatment of immune-mediated skin diseases. PN-881 targets three IL-17 dimers (IL-17 AA, AF and FF), and may offer potential treatment options for plaque psoriasis, psoriatic arthritis (“PsA”), h idradenitis suppurativa (“HS”), and spondyloarthritis. In October 2025, the first human subject was dosed in our Phase 1 trial of PN-881 (ClinicalTrials.gov identifier NCT07153146) evaluating its safety, tolerability, pharmacokinetics and pharmacodynamics in healthy adults. Results of the PN-881 Phase 1 study are expected to inform the design and dosing in a subsequent dose-ranging psoriasis trial. We expect to complete the Phase 1 study in mid-2026 and initiate a Phase 2 study of PN-881 in psoriasis by the end of 2026. Obesity Program PN-477 . In June 2025, we nominated PN-477, a potential best-in-class novel triple GLP-1, GIP and GCG receptor agonist peptide with oral (“PN-477o”) and subcutaneous (“PN-477sc”) routes of administration, as a development candidate for the treatment of obesity. We designed PN-477 to offer an optimal combination of total body weight loss, improved gastrointestinal tolerability and fat to lean mass ratio, with the dosing convenience of a once-daily oral agent and the added optionality of a once-weekly subcutaneous administration.…