Targeting IL-23 Could Still Be Important for Axial SpA Treatment

Sara Freeman

September 21, 2021

Interleukin-23 (IL-23) inhibition may still have a role to play in the treatment of patients with axial spondyloarthritis (SpA), suggests research presented at the 12th International Congress on Spondyloarthritides.

There is a strong rationale for using IL-23 inhibitors in patients with axial SpA, and the IL-23/IL-17 axis has been proposed as a critical player in the pathophysiology of the disease. But around 2018 it became clear from randomized, controlled trials that IL-23 inhibition was ineffective at improving key clinical outcomes, at least in patients with axial disease.

Although the overall results of a systematic review and meta-analysis that was presented at the meeting corroborated the negative results seen with IL-23–inhibiting agents in clinical trials, there were some data showing benefits of the IL-23 inhibitor risankizumab on secondary outcomes in one trial.

To look at the available evidence, Louise Vanhoutte, a second-year internal medicine student at University Hospitals Leuven (Belgium) worked under the guidance of Rik Lories, MD, PhD, head of the division of rheumatology at University Hospitals Leuven. Together they searched known databases for randomized, controlled trials investigating the use of IL-23 and IL-17 inhibitors for the treatment of adults with axial SpA or psoriatic arthritis. Studies could be either phase 2 or phase 3, but had to have included a placebo and used the ASAS40 (40% Improvement in Assessment of SpondyloArthritis International Society Response criteria), ASAS20, Bath Ankylosing Spondylitis Disease Activity Index, or SPARCC (Spondyloarthritis Research Consortium of Canada) index score to assess outcomes.

The systematic review whittled the number of clinical trials in the meta-analysis to 12, which concerned the use of ustekinumab, an IL-12/23 inhibitor, and risankizumab, along with two IL-17 inhibitors, ixekizumab and secukinumab. Data for the IL-23 inhibitors guselkumab and tildrakizumab were not available.

"To no surprise, forest plots showed that there was a lack of efficacy for IL-23 agents in the treatment of axial spondyloarthritis and a superior efficacy for IL-17 inhibitors in the treatment of axial spondyloarthritis," Vanhoutte reported.

The respective odds ratios for IL-23 and IL-17 inhibitors in getting patients to meet ASAS40 response criteria in comparison to baseline were 1.51 (95% CI, 0.98 - 2.31) and 2.54 (95% CI, 2.02 - 3.19).

"Does this mean it is a dead-end street for all IL-23 inhibition?" she asked. Not necessarily.

In the meta-analysis, not only did risankizumab lower the Ankylosing Spondylitis Disease Activity Score based on C-reactive protein (ASDAS-CRP) by a mean difference (MD) of –0.30 (95% CI, –0.41 to –0.19) from baseline values, but it also led to statistically significant reductions in SPARCC index score for the spine (MD, –3.10; 95% CI, –4.50 to –1.70) and high-sensitivity CRP (MD, –2.10; 95% CI, –2.56 to –1.64). The risankizumab findings might suggest there are potential disease-modifying properties for specifically targeting IL-23p19. There could also be a window of opportunity to use IL-23 inhibitors earlier.

"These are only results from one randomized, controlled trial in a small sample size where outcomes were reported as medians and interquartile ranges, so they had to be converted to means and standard deviations to have an odds ratio in the end," she explained.

"Also, these were results from a radiographic axial spondyloarthritis population and not a nonradiographic axial spondyloarthritis population," she added.

While that might limit the interpretation of the findings, "what we see here is both reduction in inflammation and reduction in structural disease progression as [measured] by SPARCC," Vanhoutte said.

"Since IL-23 is an upstream molecule from IL-17 it's probable that IL-23 is present in the prephase of the disease, in a prephase inflammation state," she hypothesized. "This is especially interesting because there are very few randomized, controlled trials that examine therapeutic agents in nonradiographic axial spondyloarthritis," she observed. Looking at IL-23 in radiographic, or established, disease therefore may not be as useful.

"I'm thinking you're making actually a very important point for us," commented Robert Landewé, MD, PhD, of Amsterdam University Medical Center.

"We are discussing whether or not IL-23 is important in inhibiting the disease activity of patients with axial spondyloarthritis, and we are surprised that it is not shown in RCTs.

"Why is it completely ineffective in axial spondyloarthritis? You show us that that is probably not the case," Landewé suggested.

"What you make very clear here is that indeed there is some efficacy, and from a pathophysiological way of thinking it might be slightly different as compared with what most clinicians nowadays think."

The study had no specific funding, and no disclosures were reported.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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