FDA’s Approval of Remibrutinib for CSU, With Giselle Mosnaim, MD

The US Food and Drug Administration (FDA) has approved remibrutinib, a selective Bruton’s tyrosine kinase (BTK) inhibitor, for adults with chronic spontaneous urticaria (CSU).1,2 The approval, announced on September 30, 2025, by Novartis, provides a new oral option for patients whose symptoms remain uncontrolled despite H1-antihistamines, offering an alternative to injectable biologics like omalizumab.

“If patients fail second generation on [folding or up-dosing] the standard dose, the current guidelines [recommend advancing to biologics],” Giselle Mosnaim, MD, a clinical associate professor at the University of Chicago’s Pritzker School of Medicine, and an allergist at NorthShore University HealthSystem, said in an interview with HCPLive. “It is very exciting that remibrutinib… a BTK inhibitor…is a twice daily oral medication to treat CSU.”

HCPLive spoke with Mosnaim ahead of the FDA approval to discuss the unmet need in the CSU space, where remibrutinib fits in the treatment landscape, and what role Bruton’s tyrosine kinase inhibitors like remibrutinib may have in other allergic or inflammatory conditions. Mosnaim served as an investigator in the phase 3 REMIX-1 and REMIX-2 trials, which assessed the safety and efficacy of remibrutinib for CSU.

Remibrutinib inhibits the BTK pathway, reducing histamine release from mast cells and targeting the underlying mechanism of CSU. In the REMIX-1 and REMIX-2 trials, the drug produced rapid, meaningful reductions in weekly urticaria activity scores (UAS7) at 12 weeks, with benefits maintained through 52 weeks. Participants taking remibrutinib 25 mg twice daily also experienced substantial improvements in itch severity scores and hive severity scores (HSS7) at 12 weeks, compared with placebo.3,4

Nearly half of the participants achieved UAS7 ≤ 6, and roughly a third reached complete symptom resolution (UAS7 = 0). Participants initially on placebo who switched to remibrutinib at 24 weeks experienced rapid, sustained relief.3,4

“I think that… some patients will prefer to go from high dose [antihistamines] to remibrutinib because it is an oral option,” Mosnaim said. “And so, rather than going to an injectable therapy, they can go to a fast-acting oral.”

The REMIX trials also demonstrated a favorable safety profile. The most common adverse events—respiratory infections and headaches—were mild and reversible. No serious adverse events were linked to the drug, and laboratory monitoring was minimal.3,4

“It has a fast onset of action, and it has an excellent efficacy profile,” Mosnaim said. “It's very exciting because our patients with CSU want to have fast relief, [and with] having [an itch] and hives and swelling, you want symptom relief as fast as possible.”

References

1. Derman C. FDA Approves Remibrutinib for Chronic Spontaneous Urticaria. HCPLive. Published September 30, 2025. Accessed September 30, 2025. https://www.hcplive.com/view/fda-approves-remibrutinib-chronic-spontaneous-urticaria

2. Novartis Pharma AG. Novartis receives FDA approval for Rhapsido® (remibrutinib), the only oral, targeted BTKi treatment for chronic spontaneous urticaria (CSU). GlobeNewswire News Room. Published September 30, 2025. Accessed September 30, 2025. https://www.globenewswire.com/news-release/2025/09/30/3159065/0/en/Novartis-receives-FDA-approval-for-Rhapsido-remibrutinib-the-only-oral-targeted-BTKi-treatment-for-chronic-spontaneous-urticaria-CSU.html

3. Novartis Phase III data confirm sustained efficacy and long-term safety of oral remibrutinib in chronic spontaneous urticaria. Novartis. https://www.novartis.com/news/media-releases/novartis-phase-iii-data-confirm-sustained-efficacy-and-long-term-safety-oral-remibrutinib-chronic-spontaneous-urticaria

4. Metz M, Giménez-Arnau A, Hide M, et al. Remibrutinib in Chronic Spontaneous Urticaria. N Engl J Med. 2025;392(10):984-994. doi:10.1056/NEJMoa2408792