PeptiDream Inc., a public Kanagawa, Japan-based biopharmaceutical company (President: Patrick C. Reid, hereinafter “PeptiDream”)(Tokyo: 4587) announced its second oral peptide therapeutic program entering into its Clinical Development Portfolio – a dual IL-17A and IL-17F macrocyclic peptide inhibitor targeting the major dimeric forms of interleukin-17 (IL-17AA, IL-17AF, IL-17FF) – at their 2025 R&D Day held on December 5, 2025. The development candidate demonstrated biologic-like efficacy in preclinical models when orally administered, aiming to deliver a deeper and more durable response across skin and musculoskeletal manifestations, improving patient quality of life.

The IL17 pathway is a clinically validated therapeutic target across several major autoimmune diseases, including psoriasis, psoriatic arthritis, and ankylosing spondylitis. Although today’s approved IL17 inhibitors deliver excellent clinical outcomes, all are injectable biologics, which can limit convenience and long-term accessibility. PeptiDream’s oral IL17 macrocyclic peptide is designed to change this paradigm—offering the potential for biologiclike efficacy with the benefits of oral administration, as well as the versatility for monotherapy or combination therapy with TNF or JAK inhibitors, providing new options for patients with difficulttotreat disease.

Key Highlights of the Program:

• Potent Orally Bioavailable Macrocyclic Peptide: Engineered for high-affinity and stability to achieve oral bioavailability and biologic-like potency
• Inhibits Critical IL-17 Isoforms: Designed to inhibit not only IL-17A/A, IL-17A/F, but also IL-17F/F, associated with deeper and more durable clinical responses
• Enhanced Tissue Penetration: The macrocyclic peptide candidate’s small size enables improved distribution and potential for superior tissue-localized activity
• Broad Therapeutic Opportunity: An oral therapy with the potential to treat a broad range of IL17-mediated diseases, unlocking new monotherapy and combination therapy approaches.

“We’re pioneering a new era in autoimmune treatment with next‑generation oral peptide therapeutics. Although injectable biologics can achieve PASI 90 responses in as many as 85% of patients, their reliance on injections and in‑office administration limits convenience and flexibility.” said Patrick C. Reid, Ph.D., President & CEO of PeptiDream. “Our oral, dual IL‑17A/IL‑17F macrocyclic peptide inhibitor represents a revolution in autoimmune treatment—bringing biologic‑level performance into an easy‑to‑take pill. As IL‑17 biologics continue to anchor psoriasis therapy, an effective oral alternative has the potential to meaningfully broaden access, improve patient experience, and raise the standard of care. Positioned for both monotherapy use and combination strategies, this program is designed to drive better outcomes for millions of patients globally. We are eager to advance it into the clinic and unlock what we believe can be a best‑in‑class therapy.”

PeptiDream’s oral dual IL‑17A and IL-17F inhibitor was discovered using its proprietary PDPS^® technology and optimized for potency and oral bioavailability. In an IL‑17 in vivo challenge model, oral dosing of our peptide significantly reduced CXCL1 levels to the same extent as IV administration of an approved IL‑17 biologic. Notably, greater skin distribution versus plasma was observed at 24 hours—a key differentiator over current biologics. Building on these encouraging results, PeptiDream is advancing the program into IND-enabling studies with a view toward clinical trials, while exploring strategic partnerships to accelerate global development and deliver a best-in-class oral therapy for autoimmune disease patients worldwide.

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Our oral, dual IL-17A/IL-17F macrocyclic peptide inhibitor represents a revolution in autoimmune treatment—bringing biologic-level performance into an easy-to-take pill.