$50 million milestone payment triggered by FDA approval; Protagonist is eligible to receive 6 - 10% royalties on sales and up to $580 million in future milestone payments

Webcast and conference call to be held at 8:30 am ET on March 18

NEWARK, CA / ACCESS Newswire / March 18, 2026 / Protagonist Therapeutics, Inc. (NASDAQ: PTGX) ("Protagonist" or "the Company") announced today that Johnson & Johnson received U.S. Food and Drug Administration (FDA) approval for ICOTYDE^™ (icotrokinra), an interleukin-23 (IL-23) receptor antagonist for the treatment of moderate-to-severe plaque psoriasis in adults and pediatric patients 12 years of age and older who weigh at least 40 kg who are candidates for systemic therapy or phototherapy. ICOTYDE is the first and only targeted oral peptide that precisely blocks the IL-23 receptor.

ICOTYDE will be commercialized by Johnson & Johnson under the license and collaboration agreement established in 2017 between Protagonist and Janssen Biotech, Inc., a Johnson & Johnson company. ICOTYDE was jointly discovered by Protagonist and Johnson & Johnson scientists, with Protagonist having primary responsibility for the development of ICOTYDE through Phase 1, and Johnson & Johnson assuming responsibility for further development and commercialization.

FDA approval of ICOTYDE triggers a $50 million milestone payment to Protagonist. Protagonist is eligible to receive up to $580 million in potential additional regulatory and sales milestone payments, as well as tiered royalties ranging from 6% to 10% on global net sales, corresponding to 7.25% on a weighted-average basis at $4 billion in annual sales, with the top royalty tier of 10% applying to sales above $4 billion.

"ICOTYDE offers a novel plaque psoriasis treatment that combines the established efficacy and safety of IL-23 pathway blockade with the convenience of a once-daily oral pill. The FDA approval of ICOTYDE reflects a successful culmination of years of groundbreaking research and clinical development that began over 13 years ago in our laboratories and demonstrates the strength of our peptide technology platform to generate innovative therapies," said Dinesh V. Patel, PhD, President and Chief Executive Officer of Protagonist Therapeutics. "I am incredibly proud of our team's dedication and commitment to addressing unmet medical needs and making a meaningful difference in the lives of patients."

"I would also like to congratulate Johnson & Johnson for maintaining a productive and seamless collaboration ongoing since 2017 as this novel medicine was advanced from discovery through development and finally to FDA approval," Patel continued. "We look forward to results from ongoing clinical studies evaluating ICOTYDE in additional IL-23-driven diseases, including psoriatic arthritis, ulcerative colitis, and Crohn's disease. With the pending FDA decision for rusfertide this year, and the financial resources for accelerating pipeline investment, we're confident this is the beginning of a multi-year product-driven growth cycle for Protagonist Therapeutics."

ICOTYDE was developed using Protagonist's proprietary peptide technology platform. The Company continues to invest in its discovery engine and development pipeline, with multiple programs moving towards proof-of-concept trials designed to produce therapeutics with clinically relevant competitive differentiation.

Clinical evidence summary
ICOTYDE met all primary endpoints and demonstrated a favorable safety profile across four Phase 3 studies including 2,500 patients. The approval is based on an unprecedented body of evidence from the ICONIC clinical development program, which simultaneously evaluated ICOTYDE in adults and adolescents, high impact sites such as scalp and genital PsO, and in duplicate head-to-head trials versus an active comparator. In the head-to-head studies, approximately 70% of patients achieved clear or almost clear skin (IGA 0/1) and 55% of patients achieved a Psoriasis Area and Severity Index (PASI)90 response at Week 16. Rates of adverse reactions for ICOTYDE treated patients were within 1.1% of placebo through Week 16 and no new safety signals were identified through Week 52.

Additional studies underway in other disease areas include: ICONIC-PsA 1 (NCT06878404) and ICONIC-PsA 2 (NCT06807424) in active psoriatic arthritis; ICONIC-UC (NCT071196748) in moderately to severely active ulcerative colitis; and ICONIC-CD (NCT7196722) in moderately to severely active Crohn's disease.

Conference Call and Webcast Details
The dial-in numbers for Protagonist's investor update on March 18^th at 8:30 am ET are:
US-based Investors: 1-877-407-0752
International Investors: 1-201-389-0912
Conference Call ID: 13759426

The webcast link for the event can be found here:
https://viavid.webcasts.com/starthere.jsp?ei=1756753&tp_key=f99979a28e

A replay will be available on the Company's Investor Relations Events and Presentations webpage following the event.

Unmet need in moderate to severe plaque psoriasis
Psoriasis affects more than eight million Americans, impacting physical comfort and quality of life, especially when lesions are on visible or sensitive areas. For many with moderate to severe disease, targeted systemic treatments are key. This aligns with International Psoriasis Council guidance to transition to systemic therapy if two cycles of topical medications applied for four weeks fail to bring meaningful improvement.

About ICOTYDE™ (icotrokinra)
ICOTYDE is the first and only targeted oral peptide designed to precisely block the IL-23 receptor, which underpins the inflammatory response in moderate to severe plaque PsO. ICOTYDE binds to the IL-23 receptor with high affinity and demonstrated potent inhibition of IL-23 signaling in human T cells. Clinical significance of these findings are unknown.

ICOTYDE is currently approved in the U.S. for the treatment of adults, and pediatric patients 12 years of age and older who weigh at least 40 kg, with moderate to severe plaque PsO who are candidates for systemic therapy or phototherapy. Patients on ICOTYDE take one pill, once a day with water upon waking, 30 minutes prior to eating food.

ICOTYDE is also currently in Phase 3 studies for active psoriatic arthritis, moderately to severely active ulcerative colitis and moderately to severely active Crohn's disease.

FullICOTYDE^™ prescribing information will be available on the ICOTYDE^™ website.

About Plaque Psoriasis
Plaque psoriasis (PsO) is a chronic immune-mediated disease resulting in overproduction of skin cells, which causes inflamed, scaly plaques that may be itchy or painful. It is estimated that 8 million Americans and more than 125 million people worldwide live with the disease. Nearly one-quarter of all people with plaque PsO have cases that are considered moderate to severe. On Caucasian skin, plaques typically appear as raised, red patches covered with a silvery white buildup of dead skin cells or scale. On skin of color, the plaques may appear darker and thicker, and more of a purple, gray, or dark brown color. Plaques can appear anywhere on the body, although they most often appear on the scalp, knees, elbows, and torso. Living with plaque PsO can be a challenge and impact life beyond a person's physical health, including emotional health, relationships, and handling the stressors of life. Psoriasis on highly visible areas of the body or sensitive skin, such as the scalp, hands, feet, and genitals, can have an increased negative impact on quality of life.

About Protagonist
Protagonist Therapeutics is a discovery through late-stage development biopharmaceutical company. The Company's proprietary peptide technology platform enables de novo discovery of peptide therapeutics. Two novel peptides derived from Protagonist's proprietary discovery platform are at or near commercialization. ICOTYDE^™ (icotrokinra) is approved in the U.S. for the treatment of moderate-to-severe plaque psoriasis in adults and pediatric patients 12 years of age and older who weigh at least 40 kg who 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) licensed to Janssen Biotech, Inc.,a Johnson & Johnson company. ICOTYDE was jointly discovered by Protagonist and Johnson & Johnson scientists, with Protagonist having primary responsibility for the development of ICOTYDE through Phase 1, and Johnson & Johnson assuming responsibility for further development and commercialization. An NDA for rusfertide, a first-in-class hepcidin mimetic peptide that is being co-developed with Takeda Pharmaceuticals pursuant to a worldwide license and collaboration agreement entered in 2024, is under priority review with the FDA. Protagonist holds an option to co-commercialize rusfertide in the U.S. through a 50/50 profit and loss share structure or can opt-out of this structure. The Company also has a number of preclinical stage drug discovery programs addressing clinically and commercially validated targets including an oral IL-17 peptide antagonist, obesity dual and triple agonists, an oral hepcidin functional mimetic, and the recently announced IL-4 and amylin programs.

More information on Protagonist, its pipeline drug candidates, and clinical studies can be found on the Company's website at https://www.protagonist-inc.com.

Cautionary Note on Forward-Looking Statements
This press release contains forward-looking statements for purposes of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Forward-looking statements include statements regarding the potential benefits of ICOTYDE and potential revenue from the Company's collaboration with Johnson & Johnson. In some cases, you can identify these statements by forward-looking words such as "anticipate," "believe," "may," "will," "expect," or the negative or plural of these words or similar expressions. Forward-looking statements are not guarantees of future performance and are subject to risks and uncertainties that could cause actual results and events to differ materially from those anticipated, including, but not limited to, our ability to develop and commercialize our product candidates, our ability to earn milestone payments under our collaboration agreements with Janssen and Takeda, our ability to use and expand our programs to build a pipeline of product candidates, our ability to obtain and maintain regulatory approval of our product candidates, our ability to operate in a competitive industry and compete successfully against competitors that have greater resources than we do, and our ability to obtain and adequately protect intellectual property rights for our product candidates. Additional information concerning these and other risk factors affecting our business can be found in our periodic filings with the Securities and Exchange Commission, including under the heading "Risk Factors" contained in our most recently filed periodic reports on Form 10-K and Form 10-Q filed with the Securities and Exchange Commission. Forward-looking statements are not guarantees of future performance, and our actual results of operations, financial condition, and liquidity, and the development of the industry in which we operate, may differ materially from the forward-looking statements contained in this press release. Any forward-looking statements that we make in this press release speak only as of the date of this press release. We assume no obligation to update our forward-looking statements, whether as a result of new information, future events, or otherwise, after the date of this press release.

Investor Relations Contact
Corey Davis, Ph.D.
LifeSci Advisors
cdavis@lifesciadvisors.com
+1 212 915 2577

Media Relations Contact
Virginia Amann
ENTENTE Network of Companies
virginiaamann@ententeinc.com
+1 833 500 0061 ext 1

SOURCE: Protagonist Therapeutics