Idorsia initiates a proof-of-concept trial with its oral first-in-class selective CCR6 antagonist

• The trial aims to establish clinical proof-of-concept in psoriasis and proof-of-mechanism for other CCR6- and Th17-associated autoimmune indications

Allschwil, Switzerland – January 6, 2026
Idorsia Ltd (SIX: IDIA) announces the initiation of a Phase 2 proof-of-concept trial evaluating IDOR-1117-2520 for participants with moderate-to-severe psoriasis. IDOR-1117-2520 is Idorsia’s first-in-class, oral, selective CCR6 receptor antagonist designed to block the CCR6/CCL20 axis and prevent the migration of disease-driving Th17 immune cells.

Psoriasis is a chronic, immune-mediated skin condition driven by the IL-23/Th17 pathway, characterized by elevated CCL20 and CCR6-positive cells in affected skin.¹ There is a significant need for oral drugs with innovative mechanisms of action that address Th17-driven conditions such as psoriasis.

The 12-week exploratory Phase 2 proof-of-concept trial will evaluate whether CCR6 blockade improves psoriasis by preventing pathogenic immune cells from reaching the skin. Two dosages of the once-daily oral drug will be tested against placebo, using established clinical endpoints such as Psoriasis Area and Severity Index (PASI) and biomarkers including beta-defensin 2, a key indicator of disease activity.² Psoriasis is a well-validated indication to demonstrate clinical proof-of-mechanism for targeting of the IL-23/Th17 pathway that matches Idorsia’s ambition for its investigational compound.

Alberto Gimona MD, Head of Global Clinical Development at Idorsia, commented:
“The potential for an oral therapy that delivers biologic-like efficacy is compelling. We’ve designed a trial that evaluates the speed and magnitude of response, dose performance, and safety in a well-characterized Th17-driven disease. A positive outcome would confirm clinical proof-of-concept in psoriasis and mechanistic validation for expansion into other CCR6- and Th17-associated indications.”

About the proof-of-concept trial
This multicenter, double-blind, randomized, placebo-controlled, Phase 2 proof-of-concept trial will explore the efficacy and safety of IDOR-1117-2520 in adults with moderate-to-severe chronic plaque psoriasis, with or without psoriatic arthritis. Approximately 30 participants will be randomized to receive one of two doses of IDOR-1117-2520 or placebo once daily. Efficacy will be measured through the primary endpoint of change from baseline to Week 12 in PASI score. Results are expected in the first quarter of 2027.

Martine Clozel, MD, Chief Scientific Officer and Head of Research at Idorsia, commented:
“Idorsia has a rich heritage in G-Protein Coupled Receptor (GPCR) research and drug discovery, and we have built a portfolio of chemokine projects where GPCRs play an important pathogenic role, opening the way to address clear medical needs. IDOR-1117-2520 is the first to enter Phase 2 development. We’ve chosen our first-in-class, once-a-day oral CCR6 receptor antagonist based on its selectivity and potency for the CCR6 receptor, a novel target in the inflammatory cascade in Th17-driven diseases. This trial in patients with psoriasis will elucidate the profile of our unique compound and if positive will support secondary selection of the best CCR6-driven target indications for further development – either independently or in partnership.”

About CCR6 antagonism
CCR6 antagonism targets a key receptor that directs pathogenic immune cells toward inflamed tissues through the CCL20-CCR6 axis.^3-8 In many immune-mediated diseases, CCL20 is strongly upregulated, attracting CCR6-positive cells such as Th17-lineage lymphocytes.^3-8 Blocking CCR6 prevents these cells from migrating from the bloodstream into the inflamed peripheral tissues. The prevention of this migration inhibits the Th17 pathway, which is well understood and consistent across psoriasis, psoriatic arthritis, rheumatoid arthritis, inflammatory bowel disease, and other Th17-associated conditions.^3-8 CCR6 antagonism therefore offers a targeted approach to modulating inflammation without broad immunosuppression.

AboutIDOR-1117-2520
IDOR-1117-2520 is a first-in-class, oral small-molecule, selective CCR6 receptor antagonist that blocks CCL20-driven recruitment of pathogenic CCR6-expressing immune cells. In preclinical models, the compound prevented CCR6-positive cell migration and achieved efficacy comparable to inhibitors of IL-17 and IL-23, supporting its relevance across multiple Th17-mediated autoimmune diseases.⁹ Phase 1 data confirmed a safety and pharmacokinetics profile supporting further investigation with once-daily dosing.

IDOR-1117-2520 is now in a Phase 2 proof-of-concept trial in psoriasis, with the potential to expand into additional autoimmune conditions where the CCR6-CCL20 pathway plays a pathogenic role.

Notes to the editor

About Th17-mediated immune disorders
Th17-driven immune disorders are characterized by excessive recruitment of auto-reactive inflammatory immune cells to tissues, where they release cytokines such as IL-17 that perpetuate chronic inflammation.^10,11 These cells are drawn toward areas of disease by elevated CCL20, which signals through CCR6. Multiple autoimmune conditions share this pathology, including psoriasis, psoriatic arthritis, rheumatoid arthritis, inflammatory bowel disease and multiple sclerosis ^3-8 Existing therapies that block IL-17 or IL-23 validate this pathway clinically but are mostly injectable biologics.^12-14 A targeted oral therapy acting on the CCR6-CCL20 axis could address substantial unmet need across this group of diseases, and offer patients a more convenient treatment option.

References:

1. Griffiths, C. E. M., Armstrong, A. W., Gudjonsson, J. E., & Barker, J. (2021). Psoriasis. Lancet, 397(10281), 1301–1315.
2. Kolbinger F, Loesche C, Valentin MA, Jiang X, Cheng Y, Jarvis P, Peters T, Calonder C, Bruin G, Polus F, Aigner B, Lee DM, Bodenlenz M, Sinner F, Pieber TR, Patel DD. β-Defensin 2 is a responsive biomarker of IL-17A-driven skin pathology in patients with psoriasis. J Allergy Clin Immunol. 2017 Mar;139(3):923-932.e8.
3. Meitei HT, Jadhav N, Lal G. CCR6-CCL20 axis as a therapeutic target for autoimmune diseases. Autoimmun Rev. 2021 Jul;20(7):102846. doi: 10.1016/j.autrev.2021.102846. Epub 2021 May 7. PMID: 33971346.
4. Gómez-Melero S, Caballero-Villarraso J. CCR6 as a Potential Target for Therapeutic Antibodies for the Treatment of Inflammatory Diseases. Antibodies (Basel). 2023 Apr 20;12(2):30. doi: 10.3390/antib12020030. PMID: 37092451; PMCID: PMC10123731.
5. Comerford I, Bunting M, Fenix K, Haylock-Jacobs S, Litchfield W, Harata-Lee Y, Turvey M, Brazzatti J, Gregor C, Nguyen P, Kara E, McColl SR. An immune paradox: how can the same chemokine axis regulate both immune tolerance and activation?: CCR6/CCL20: a chemokine axis balancing immunological tolerance and inflammation in autoimmune disease. Bioessays. 2010 Dec;32(12):1067-76. doi: 10.1002/bies.201000063. Epub 2010 Oct 15. PMID: 20954179.
6. Wang L, Hong X, Du H. Association Between Serum Chemokine Ligand 20 Levels and Disease Activity and Th1/Th2/Th17-Related Cytokine Levels in Rheumatoid Arthritis. J Interferon Cytokine Res. 2023 Nov;43(11):512-517. doi: 10.1089/jir.2023.0057. Epub 2023 Oct 9. PMID: 37815793.
7. Stallhofer J, Reichl F, Lauseker M, Waldenmaier L, Török HP, Mayerle J, Olszak T, Schnitzler F, Frasheri I, Breiteneicher S, Brand S, Stallmach A, Diegelmann J, Beigel F. CCL20 expression is elevated in inflammatory bowel disease and attenuated by vitamin D metabolites. Sci Rep. 2025 Jun 20;15(1):20145. doi: 10.1038/s41598-025-05094-x. PMID: 40542081; PMCID: PMC12181267.
8. Jafarzadeh A, Bagherzadeh S, Ebrahimi HA, Hajghani H, Bazrafshani MR, Khosravimashizi A, Nemati M, Gadari F, Sabahi A, Iranmanesh F, Mohammadi MM, Daneshvar H. Higher circulating levels of chemokine CCL20 in patients with multiple sclerosis: evaluation of the influences of chemokine gene polymorphism, gender, treatment and disease pattern. J Mol Neurosci. 2014 Jul;53(3):500-5. doi: 10.1007/s12031-013-0214-2. Epub 2014 Jan 7. PMID: 24395091.
9. Kulig P, Brazauskas P, Suffiotti M, Raoult E, Babilonski U, Renault B, Grieder U, Vezzali E, Blattmann P, Martinic MM, Murphy MJ. Efficacy of IDOR-1117-2520, a novel, orally available CCR6 antagonist in preclinical models of skin dermatitis. Br J Pharmacol. 2025 Aug;182(15):3452-3475. doi: 10.1111/bph.70025. Epub 2025 Mar 28. PMID: 40156059.
10. Furue, M., Furue, K., Tsuji, G., & Nakahara, T. (2020b). Interleukin-17a and keratinocytes in psoriasis. International Journal of Molecular Sciences, 21(4), 1275.
11. Ferris, L. K., Ott, E., Jiang, J., Hong, H. C., Li, S., Han, C., & Baran, W. (2020). Efficacy and safety of guselkumab, administered with a novel patient-controlled injector (one-press), for moderate-to-severe psoriasis: Results from the phase 3 ORION study. The Journal of Dermatological Treatment, 31(2), 152–159.
12. Papp, K. A., Leonardi, C., Menter, A., Ortonne, J. P., Krueger, J. G., Kricorian, G., & Baumgartner, S. (2012). Brodalumab, an anti-interleukin-17-receptor antibody for psoriasis. The New England Journal of Medicine, 366(13), 1181–1189.
13. Paul, C., Lacour, J. P., Tedremets, L., Kreutzer, K., Jazayeri, S., Adams, S., & group, J. s. (2015). Efficacy, safety and usability of secukinumab administration by autoinjector/pen in psoriasis: A randomized, controlled trial (JUNCTURE). Journal of the European Academy of Dermatology and Venereology, 29(6), 1082–1090.
14. Reich, K., Griffiths, C. E. M., Gordon, K. B., Papp, K. A., Song, M., Randazzo, B., & Blauvelt, A. (2020). Maintenance of clinical response and consistent safety profile with up to 3 years of continuous treatment with guselkumab: Results from the VOYAGE 1 and VOYAGE 2 trials. Journal of the American Academy of Dermatology, 82(4), 936–945.

About Idorsia
The purpose of Idorsia is to challenge accepted medical paradigms, answering the questions that matter most. To achieve this, we will discover, develop, and commercialize transformative medicines – either with in-house capabilities or together with partners – and evolve Idorsia into a leading biopharmaceutical company, with a strong scientific core.

Headquartered near Basel, Switzerland – a European biotech hub – Idorsia has a highly experienced team of dedicated professionals, covering all disciplines from bench to bedside; QUVIVIQ™ (daridorexant), a different kind of insomnia treatment with the potential to revolutionize this mounting public health concern; strong partners to maximize the value of our portfolio; a promising in-house development pipeline; and a specialized drug discovery engine focused on small-molecule drugs that can change the treatment paradigm for many patients. Idorsia is listed on the SIX Swiss Exchange (ticker symbol: IDIA).

For further information, please contact:
George Thampy
Senior Vice President, Head of Investor Relations
Idorsia Pharmaceuticals Ltd, Hegenheimermattweg 91, CH-4123 Allschwil
+41 58 844 10 10
investor.relations@idorsia.com – media.relations@idorsia.com – www.idorsia.com

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