Remibrutinib
Bruton tyrosine kinase inhibitor · also known as Rhapsido, LOU064
Bruton tyrosine kinase inhibitor studied in cultured human mast cells and approved by the FDA for chronic spontaneous urticaria.
- How it relates to mast cells
- Mast cells in the laboratory
- Types of studies cited
- Human mast cells in vitro
- Approved in the US for
- chronic spontaneous urticaria
- Randomised trials in
- chronic spontaneous urticaria
What this relationship means: Studied on mast cells directly, but in cell culture or animals rather than in people. The study-design field distinguishes human cells from non-human models. A mechanism demonstrated in a dish is a reason to investigate, not a result — and the concentrations used are frequently ones that human exposure does not reach.
Mechanism of action
Remibrutinib is a small-molecule inhibitor of Bruton tyrosine kinase (BTK), an intracellular signalling protein used by FcεRI and other immune receptors. The FDA label identifies BTK in mast cells, basophils, B cells, macrophages, and thrombocytes, and notes activity against the related kinases TEC and BMX.
In laboratory work, researchers exposed CD34-derived human mast cells and blood basophils to IgE cross-linking or serum from people with chronic urticaria. Remibrutinib reduced the activation marker CD63 under those experimental conditions. That experiment demonstrates a mast-cell mechanism in culture; it does not establish an MCAS outcome.
Two randomised, placebo-controlled phase 3 trials were published in chronic spontaneous urticaria, and the current US label carries that indication for adults who remain symptomatic despite H1-antihistamine treatment. The label explicitly limits the indication to chronic spontaneous urticaria rather than other forms of urticaria, and it does not include MCAS.
Sources
- Rhapsido (remibrutinib) current US prescribing information Drug label 2025 · link checked 21 Aug 2026
- Remibrutinib inhibits hives effector cells stimulated by serum from chronic urticaria patients independently of FcεR1 expression level and omalizumab clinical response Peer-reviewed study 2023 PMID 36973953 · link checked 21 Aug 2026
- Remibrutinib in Chronic Spontaneous Urticaria Peer-reviewed study 2025 PMID 40043237 · link checked 21 Aug 2026