MoonLake Reports Positive Phase 2 Results for Sonelokimab in Axial Spondyloarthritis

MoonLake Immunotherapeutics announced positive topline results from the S-OLARIS Phase 2 trial of sonelokimab (SLK) in patients with radiographic and non-radiographic axial spondyloarthritis (axSpA) on February 22, 2026. The company also announced its financial results for the fourth quarter and year ended December 31, 2025.

In the Phase 2 S-OLARIS trial in axSpA, SLK demonstrated clinically meaningful and statistically significant benefit. 81% of patients treated with SLK (n=26, mNRI), achieved an Assessment of Spondyloarthritis International Society 40 (ASAS40) response at Week 12. ASAS40 measures an improvement of at least 40% and an absolute improvement of ≥2 units on a 0-10 numerical rating scale from baseline in at least three of the four key domains (Patient Global Assessment of disease activity, total back pain, physical function, inflammation), with no worsening in the remaining domain and has been the primary endpoint for the latest approved therapies.

More than 80% of patients also achieved a 'clinically important improvement' as per ASDAS-CRP score by Week 12 (mNRI). The clinical improvement, in patients treated with SLK, was confirmed by SPARCC MRI scores in the sacroiliac joint (SIJ), measuring inflammation and injury inside the bone, at week 12. This suggests rapid onset of action for SLK and IL-17A and F inhibitory activity in deep, difficult-to-access tissues.

PET imaging with an 18F-NaF tracer collected as part of the clinical trial showed significant reduction of inflammation and osteoblast activity in sacroiliac joints affected by axSpA, a key driver of irreversible ossification in the disease. axSpA is a disease driven by inflammation leading to irreversible ossification (via osteoblast activity) and ultimately to irreversible restriction of mobility. The objective PET/MRI imaging data suggest potential for disease modification in axSpA for SLK.

Objective peripheral blood and tissue biomarker analyses conducted to control for the effect of SLK, showed rapid and sustained effects of the treatment with SLK in inhibiting key immune pathways known to drive inflammation and ossification in affected patients. As a biomarker-controlled trial, S-OLARIS data showed SLK reduced the levels of key inflammatory mediators in axSpA, in peripheral blood and biopsy samples from patients.

The safety profile of SLK in the S-OLARIS trial was consistent with previous trials with no new safety signals detected. Data from this clinical trial further strengthens the potential of SLK in treating a wide array of inflammatory diseases and represents the fifth indication with positive data, in Phase 2 and Phase 3 clinical trials, for the IL-17A and F Nanobody®.

MoonLake ended the fourth quarter with $394 million in cash, cash equivalents and short-term marketable debt securities which, together with funds from its latest equity raise (gross proceeds of $75 million), are expected to provide a cash runway into the second half of 2027. The Company also announced the amendment of its debt facility with Hercules Capital, with a concurrent drawdown of $25 million, and up to $400 million in non-dilutive funds remaining available to support future funding needs.

An Investor Day webcast has been confirmed for February 23, 2026, 8.00 – 9.30 am EST (2:00 – 3.30pm CET), including an open Q&A session.