Placebo Beat Risankizumab in Adults With Severe Asthma

Walter Alexander, MS

October 27, 2021

Placebo treatment was found to be superior to treatment with risankizumab with respect to time to first asthma worsening and annualized rate of asthma worsening for adults with severe persistent asthma in a phase 2a clinical trial.

The randomized, double-blind, 24-week, parallel group, multicenter trial assessed risankizumab efficacy and safety in 214 adults with severe persistent asthma. The results were reported in The New England Journal of Medicine.

Risankizumab is a humanized, monoclonal antibody directed against subunit p19 of interleukin-23. It is approved for the treatment of moderate to severe psoriasis.

Interleukin-23 has been implicated In airway inflammation mediated by type 2 and type 17 cytokines. Noting that inhibition of interleukin-23 is effective in the treatment of psoriasis and Crohn's disease, Brightling investigated whether targeting interleukin-23 in asthma patients would improve disease control and reduce airway inflammation.

Study Details

Patients received either 90 mg of risankizumab (subcutaneous) (n = 105) or placebo (n = 109) once every 4 weeks. Time to first asthma worsening was the primary endpoint. Worsening was defined as decline from baseline on 2 or more consecutive days. Deterioration was defined as a decrease of at least 30% in the morning peak expiratory flow or an increase from baseline of at least 50% in rescue medication puffs over 24 hours. In addition, a severe asthma exacerbation or an increase of 0.75 or more points on the five-item Asthma Control Questionnaire (scores range from 0 to 6, with higher scores indicating less control) were considered to be evidence of worsening. Annualized rate of asthma worsening was a secondary endpoint.

The mean age of the patients was about 53 years; 66.5% of the patients were women.

Disappointing Results

In the risankizumab group, median time to first asthma worsening was 40 days, significantly worse than the 86 days reported for the placebo group (hazard ratio, 1.46; 95% CI, 1.05 – 2.04; P = .03). For annualized asthma worsening, the rate ratio for the comparison of risankizumab with placebo was 1.49 (95% CI, 1.12 – 1.99).

Among key secondary endpoints, the adjusted mean change in trough FEV1 from baseline to week 24 was -0.05 L in the risankizumab group and -0.01 L in the placebo group. The adjusted mean change in FEV1 after bronchodilator use from baseline to week 24 was -0.10 L in the risankizumab group and -0.03 L in the placebo group. Sputum transcriptomic pathway analysis showed that genes involved in the activation of natural killer cells and cytotoxic T cells and the activation of type 1 helper T and type 17 helper T transcription factors were downregulated by risankizumab. Rates of adverse events were similar among patients receiving risankizumab and those taking placebo.

Further Trials Unwarranted

"The findings not only failed to show benefit for any outcome but also showed asthma worsening occurred earlier and more frequently in those treated with risankizumab vs placebo," said Brightling, who is a professor in the Department of Respiratory Sciences at University of Leicester, Leicester, United Kingdom, in an interview. "This study does not support any further trials for anti-IL23 in asthma." Brightling speculated on the cause of accelerated asthma worsening with risankizumab.

"We found that the gene expression of key molecules involved in our response to infection was decreased in airway samples in those treated with risankizumab vs placebo. It is possible that the increased asthma worsening following risankizumab was related to this suppression of antimicrobial immunity," he said.

He noted that risankizumab did not affect type-2/eosinophilic inflammation, which is the target for current asthma biologics, or gene expression of T2 molecules. "That suggests that this type of inflammation would have continued in the asthma patients during the trial irrespective of receiving risankizumab or placebo," he said.

Caution With Investigating Biologicals

Downstream biologic responses to risankizumab were detectable, observed Philip G. Bardin, PhD, and Paul S. Foster, DSc, in an accompanying editorial, but there was no discernible clinical benefit, implying attenuation of apposite pathways. Current understanding of the basic science relevant to asthma, they state, offers clues to the failure of risankizumab to benefit these patients with severe asthma. Although targeting the interleukin-23 and Th17 axis with risankizumab can reduce development of pathogenic Th17 cells, interleukin-23 is not critical for the development of Th17 cells.

"In contrast to pathways operated by interleukin-5 and interleukin-4Rα, interleukin-23 has only a limited auxiliary role in amplifying type 2 responses. It is possible that the trial conducted by Brightling and colleagues failed because signalling through alternative disease pathways nullified inhibition of inter-leukin-23," the editorialists write.

Bardin and Foster further speculate that because interleukin-23 is vital for effective mucosal immunity, risankizumab may have conferred to patients a predisposition to more severe or more frequent virus-induced exacerbations. They state that generally, however, the reasons for risankizumab's poorer outcomes compared to placebo are unclear. They conclude, "Overall, these findings support a cautious approach in future research investigating biologic therapies in asthma."

The clinical trial was sponsored and funded by BI/AbbVie.

N Engl J Med. 2021; 385:1669-1679. Abstract, Editorial

Walter Alexander, MS, is a freelance medical journalist.

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