Novartis Secures FDA Approval for Rhapsido in Chronic Spontaneous Urticaria, Marking New Era in BTK Inhibitor Competition

Novartis has achieved a significant milestone with the FDA's approval of Rhapsido (remibrutinib), an oral Bruton's tyrosine kinase (BTK) inhibitor, for the treatment of chronic spontaneous urticaria (CSU) in adult patients who remain symptomatic despite H1 antihistamine treatment. This approval not only expands Novartis's portfolio in the immunology space but also sets the stage for potential competition with Sanofi in the BTK inhibitor market.

Rhapsido: A Novel Approach to Chronic Hives Treatment

Rhapsido represents a new mechanism of action in the treatment of CSU, also known as chronic hives. By inhibiting BTK signaling, the drug targets both the allergic and autoimmune components of CSU. Victor Bulto, Novartis's U.S. president, explained that BTK plays a crucial role in mast cell degranulation and the release of histamine that causes hives, as well as in B cell-mediated autoantibody production.

The approval is based on the results of the phase 3 Remix-1 and Remix-2 trials, which demonstrated Rhapsido's superiority over placebo in reducing itch, hives, and weekly urticaria activity at Week 12. Long-term data showed that almost half of the patients were completely free of itch and hives at the one-year mark.

Dr. Mark Lebwohl from the Icahn School of Medicine at Mount Sinai praised Rhapsido as "an exciting new option that has the potential to help a broad range of patients get fast relief." The drug's oral formulation and safety profile, which does not require lab monitoring, are expected to facilitate its adoption by dermatologists and patients alike.

Market Implications and Future Prospects

Novartis estimates that the target CSU population in the U.S. is about 400,000 out of approximately 1.7 million people living with the disease. With only about 20% of these target patients currently being treated with existing options like Xolair or Dupixent, Rhapsido has significant market potential.

The company is not stopping at CSU, with plans to expand Rhapsido's indications. Positive results have been seen in a phase 2 trial for food allergies, and pivotal readouts for chronic inducible urticaria and multiple sclerosis are expected in 2026. Novartis is also advancing the drug into phase 3 studies for hidradenitis suppurativa and generalized myasthenia gravis.

This expansion strategy is crucial for Novartis as it prepares for the patent expiration of Cosentyx, which generated nearly $3.2 billion in sales in the first half of 2025, towards the end of the decade.

BTK Inhibitor Competition Heats Up

Rhapsido's approval comes on the heels of Sanofi's FDA approval for Wayrilz, another BTK inhibitor, in immune thrombocytopenia. Sanofi is already advancing Wayrilz into a phase 3 study for chronic hives, setting the stage for future competition in the CSU market.

A notable difference between the two drugs lies in their binding mechanisms: Wayrilz features both noncovalent and covalent binding regions, while Rhapsido forms irreversible covalent bonds with BTK. This distinction may have implications for safety profiles, particularly in cancer treatments where reversible noncovalent BTK inhibitors are generally considered safer.

As both Novartis and Sanofi push forward with their respective BTK inhibitors in various immunological indications, the pharmaceutical industry is poised for an exciting period of innovation and competition in the treatment of chronic inflammatory conditions.