MoonLake’s sonelokimab shows strong Phase II efficacy in axSpA, challenging UCB’s Bimzelx

Sonelokimab is a single-domain antibody fragment that inhibits IL-17A and IL-17F. Evidence that IL-17A and IL-17F, a pair of cytokines, amplify inflammatory processes in axial spondyloarthritis (axSpA) have led to research programs at MoonLake and UCB. The European Commission approved UCB’s Bimzelx, an antibody that inhibits IL-17A and IL-17F, in axSpA in 2023.

While UCB has a headstart, MoonLake has identified sonelokimab’s nanobody single-domain antibody fragment technology, albumin binding and differential affinity for IL-17A versus IL-17F as factors that may give it an advantage. The biotech shared data supporting its case on Sunday.

At Week 12 of a phase II trial, 81% of the 26 patients treated with sonelokimab met the Assessment of Spondyloarthritis International Society 40 (ASAS40) response criteria. To meet the criteria, patients must improve by at least 40% on three of the four domains measured by ASAS40 and get no worse on the other domain. The domains look at disease activity, back pain, physical function and inflammation.

UCB won approval in axSpA after linking Bimzelx to a 47.7% ASAS40 response rate at Week 16. While the response rate was higher in the sonelokimab study, comparisons of data generated in different trials can be unreliable. UCB’s results come from a larger, placebo-controlled phase III trial. MoonLake enrolled people with radiographic and non-radiographic axSpA. UCB only enrolled non-radiographic patients. 

MoonLake also reported that more than 80% of patients achieved a “clinically important improvement” as per Ankylosing Spondylitis Disease Activity Score with CRP (ASDAS-CRP) score by Week 12. ASDAS-CRP assesses disease severity using clinical and laboratory data. MoonLake backed up the clinical data with imaging evidence that inflammation and injury inside the bone improved on sonelokimab.

“The complementary data from clinical outcomes, MRI and PET imaging as well as peripheral blood and tissue biomarkers confirm our hypothesis of [sonelokimab’s] ability to access deeper tissue, which is essential to optimally control this chronic rheumatological condition and prevent irreversible mobility restriction,” Kristian Reich, founder and chief scientific officer at MoonLake, said in a statement.

MoonLake’s multi-disease R&D push

The readout continues MoonLake’s efforts to recover from phase III data that caused its stock to crash last year. The phase III data came from two trials that tested sonelokimab in hidradenitis suppurativa. One trial missed its primary endpoint. Despite that, MoonLake plans to file for FDA approval in the second half of the year.

MoonLake’s other upcoming milestones include phase III data on sonelokimab in psoriatic arthritis. The multi-indication R&D program could establish sonelokimab as a challenger to Bimzelx in several settings. 

Bimzelx is approved in four indications, including hidradenitis suppurativa, psoriatic arthritis and axSpA. Growing sales of the drug informed UCB’s decision to raise its full-year outlook in December. UCB has forecast that Bimzelx will generate peak sales of more than €4 billion.