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Rilzabrutinib Rapidly Reduces Itch Severity in Adults with Chronic Spontaneous Urticaria


Late-breaking phase 2 data was presented at the 2024 American Academy of Allergy, Asthma and Immunology Annual Meeting.

Spontaneous urticaria

Image courtesy of DermNet

Spontaneous urticaria

Image courtesy of DermNet

Sanofi recently announced late-breaking, positive phase 2 data from RILECSU which demonstrated rilzabrutinib significantly improved itch, hives, and urticaria in adult patients with moderate to severe chronic spontaneous urticaria (CSU), whose symptoms are not adequately controlled by H1 antihistamines. The phase 2 results were presented in a late-breaking poster at the 2024 American Academy of Allergy, Asthma and Immunology (AAAAI) Annual Meeting in Washington, DC.1

The positive phase 2 results will form the basis of the phase 3 program which is planned to begin in 2024.

As a dose-ranging study, RILECSU, evaluated different doses of rilzabrutinib, 400mg once every evening, 400mg twice a day, and 400mg 3 times a day.

In patients who were previously naive or incomplete responders to omalizumab, rilzabrutinib 400mg 3 times a day demonstrated a significant reduction from baseline in weekly itch severity score (ISS7) at week 12, and significant changes in ISS7 were seen at week 1. Additionally, investigators noted a significant reduction from baseline to week 12 in weekly urticaria activity score and a significant reduction from baseline to week 12 in weekly hives severity score.

Overall, rilzabrutinib was well-tolerated with no events of cytopenia, bleeding, or atrial fibrillation seen with other Bruton’s tyrosine kinase inhibitors. Treatment-emergent adverse events occurring at a higher frequency with rilzabrutinib compared with placebo were diarrhea (29.3% 3 times a day and twice a day, 7.9% once every evening, 15% placebo), nausea (19.5% three times a day, 17.1% twice a day, 13.2% once every evening, 5.0% placebo), headache (9.8% 3 times a day, 14.6% twice a day, 5.3% once every evening, 0.0% placebo) and abdominal pain (0.0% 3 times a day, 12.2% twice a day, 2.6% once every evening, 5.0% placebo).

“People with CSU are living with debilitating symptoms such as intensely itchy recurrent hives, swelling, or both which can have a high impact on their day-to-day lives. These data are promising news for patients that cannot be controlled with standard-of-care antihistamines – the possibility of controlling itch rapidly with an oral medicine would offer an important advancement in the treatment of this disease,” said Marcus Maurer, MD, a professor of dermatology and allergy and executive director of the Institute of Allergology at the Charité Berlin, in the news release.

RILECSU is a 52-week phase 2 study, including a 12-week randomized, double-blind, placebo-controlled, dose-ranging, efficacy and safety period, followed by a 40-week open-label extension period. The primary end point of phase 2 was change from baseline in weekly itch severity score ISS7 at 12 weeks. Key secondary end points include change from baseline in weekly urticaria activity score at 12 weeks and change from baseline weekly hives severity score at 12 weeks.

In recent additional CSU news, Japan was the first country in the world to approve Regeneron and Sanofi’s dupilumab (Dupixent) for the treatment of CSU in patients aged 12 years and older whose disease is not adequately controlled with existing therapy.2


  1. Phase 2 results demonstrate rilzabrutinib rapidly reduced itch severity and significantly improved disease activity in adults with chronic spontaneous urticaria. News release. Sanofi. February 24, 2024. Accessed February 26, 2024. https://www.sanofi.com/en/media-room/press-releases/2024/2024-02-24-14-51-48-2834723
  2. Japan first in the world to approve Dupixent (dupilumab) for chronic spontaneous urticaria (CSU). News release. Regeneron. February 16, 2024. Accessed February 26, 2024. https://investor.regeneron.com/news-releases/news-release-details/japan-first-world-approve-dupixentr-dupilumab-chronic
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