At a Glance
- MoonLake announced positive topline Phase 2 S-OLARIS results for sonelokimab (SLK) in axSpA on February 24, 2026.
- SLK achieved 81% ASAS40 response at Week 12 with supporting MRI, PET imaging, and biomarker reductions in inflammation.
- Sonelokimab’s Nanobody design enables superior deep-tissue penetration versus traditional antibodies.
- Trial ID 2024-513498-36-00 positions SLK as the fifth positive indication, advancing toward Phase 3 and regulatory filings.
Written By: Nikita Jha, BPharm
Reviewed By: Pharmacally Editorial Team
MoonLake Immunotherapeutics a biotech company developing advanced therapies for inflammatory diseases, released topline results from its Phase 2 S-OLARIS trial on February 24, 2026.
The trial tested SLK (sonelokimab), an IL-17A and IL-17F inhibitor using Nanobody® technology, in patients with axial spondyloarthritis (axSpA), a chronic inflammatory condition affecting the spine and sacroiliac joints, causing pain, stiffness, and potential irreversible bone fusion (ossification).
AxSpA includes radiographic (visible structural damage on X-rays) and non-radiographic forms, impacting millions worldwide with limited effective treatments. Current therapies often fail to fully address deep-tissue inflammation, leading to mobility loss.
Clinical and Imaging Outcomes
In the trial, 81% of SLK-treated patients (n=26, using modified non-responder imputation or mNRI for analysis) achieved an ASAS40 response by Week 12. ASAS40 is a key benchmark: it requires at least 40% improvement and an absolute ≥2-unit gain (on a 0-10 scale) in three of four domains patient global disease assessment, back pain, physical function, and inflammation without worsening in the fourth. This matches endpoints for recently approved axSpA drugs.
Over 80% also showed “clinically important improvement” via ASDAS-CRP (Ankylosing Spondylitis Disease Activity Score using C-reactive protein), confirming broad symptom relief.
Supporting evidence came from advanced imaging
- SPARCC MRI scores revealed reduced inflammation and bone injury in sacroiliac joints (SIJ), proving SLK penetrates hard-to-reach tissues.
- PET imaging with 18F-NaF tracer demonstrated significant drops in inflammation and osteoblast activity crucial for halting ossification.
Biomarker analyses in blood and tissue verified SLK’s rapid, sustained blockade of immune pathways driving axSpA inflammation and bone changes. Safety aligned with prior trials, with no new signals.
These results mark SLK’s fifth positive Phase 2/3 indication, broadening its potential across inflammatory diseases.
Prof. Kristian Reich, MoonLake’s Founder and Chief Scientific Officer, emphasized: “The data confirm SLK’s ability to access deeper tissues, essential for controlling axSpA and preventing mobility restriction. Observed impacts within 12 weeks suggest disease-modifying potential.”
Prof. Xenofon Baraliakos, Head of Rheumatology at Rheumazentrum Ruhrgebiet Herne and EULAR President, added: “This combines clinical, imaging, and biomarker data to show how Nanobody® targeting of IL-17A/F reduces axial inflammation quickly and consistently, addressing major unmet needs.”
Nanobodies® are compact, antibody-derived VHH domains offering superior tissue penetration, stability, manufacturability, and multivalent design compared to traditional antibodies.
Sonelokimab (M1095) is an investigational ~40 kDa humanized Nanobody® featuring three covalently linked VHH domains connected by glycine-serine spacers: two for high-affinity binding to IL-17A and IL-17F (blocking IL-17A/A, A/F, and F/F dimers), and a central one for human albumin binding to enhance accumulation at inflammatory sites.
Currently advancing in lead indications like hidradenitis suppurativa (HS) and psoriatic arthritis (PsA), MoonLake is also exploring it in dermatology and rheumatology areas such as adolescent HS and palmoplantar pustulosis (PPP).
References
MoonLake Announces Positive Topline Results from its Phase 2 Clinical Trial of Sonelokimab in Axial Spondyloarthritis and Reports 2025 Financial Results, 22 February 2026, https://ir.moonlaketx.com/news-releases/news-release-details/moonlake-announces-positive-topline-results-its-phase-2-clinical
Study on the Effects of Sonelokimab for Patients with Active Axial Spondyloarthritis, 2024-513498-36-00, https://clinicaltrials.eu/trial/study-on-the-effects-of-sonelokimab-for-patients-with-active-axial-spondyloarthritis/