Remibrutinib is an orally active, selective Bruton’s tyrosine kinase (BTK) inhibitor developed for the treatment of chronic spontaneous urticaria (CSU). It is a small-molecule kinase inhibitor and is marketed in the United States as Rhapsido.
The FDA approved remibrutinib in 2025 for adults with chronic spontaneous urticaria who remain symptomatic despite H1-antihistamine treatment. The approved dosage is 25 mg twice daily.
Remibrutinib has the molecular formula C₂₇H₂₇F₂N₅O₃, molecular weight 507.54 g/mol, and CAS Registry Number 1787294-07-8.
| Parameter | Details |
|---|---|
| Product Name | Remibrutinib |
| CAS Number | 1787294-07-8 |
| PubChem CID | 118107483 |
| FDA UNII | I7MVZ8HDNU |
| ChEMBL ID | CHEMBL4483575 |
| DrugBank ID | DB16852 |
| KEGG ID | D12285 |
| Molecular Formula | C₂₇H₂₇F₂N₅O₃ |
| Molecular Weight | 507.54 g/mol |
| Drug Class | BTK inhibitor |
| Therapeutic Class | Immunomodulatory / antiallergic |
| Route | Oral |
| Approved Strength | 25 mg tablet |
| Primary Target | Bruton’s tyrosine kinase (BTK) |
FDA identifies remibrutinib as a kinase inhibitor with a molecular weight of approximately 507.54 g/mol.
The chemical name of remibrutinib is:
N-(3-{6-Amino-5-[2-(N-methylprop-2-enamido)ethoxy]pyrimidin-4-yl}-5-fluoro-2-methylphenyl)-4-cyclopropyl-2-fluorobenzamide
Its molecular formula is C₂₇H₂₇F₂N₅O₃. PubChem reports a molecular weight of 507.5 g/mol, while the FDA label gives approximately 507.54 g/mol.
Selected physicochemical descriptors from PubChem include:
Remibrutinib is approved for the treatment of chronic spontaneous urticaria (CSU) in adults who remain symptomatic despite H1-antihistamine treatment.
The approved U.S. product is supplied as 25 mg film-coated tablets, administered orally twice daily. The FDA review identifies a maximum daily dose of 50 mg.
Remibrutinib has also been investigated in other immune-mediated and inflammatory disorders, but these investigational applications should not be represented as approved indications.
Remibrutinib is a selective BTK inhibitor. Bruton’s tyrosine kinase participates in intracellular signaling downstream of the FcεRI, Fcγ receptors and B-cell receptor (BCR) pathways.
By inhibiting BTK, remibrutinib suppresses signaling involved in activation and degranulation of mast cells and basophils and reduces release of histamine and other inflammatory mediators involved in urticaria.
FDA notes that remibrutinib also inhibits the related kinases TEC and BMX.
Remibrutinib is a synthetic small-molecule API and requires conventional pharmaceutical chemical characterization.
Appropriate quality testing includes:
The EMA assessment report specifically states that the active-substance specification includes appearance, particle size, IR, XRPD, related substances by HPLC, residual solvents, water by Karl Fischer, sulphated ash, phosphorus content by ICP-OES, specific GC/HPLC-MS impurities, assay on anhydrous and solvent-free basis, and microbiological testing.
Remibrutinib is a synthetic small-molecule pharmaceutical API manufactured through controlled chemical synthesis followed by purification and isolation.
Manufacturing controls should cover:
The regulatory assessment reports that commercial-scale batches were consistent with the proposed specification and that the active substance manufacturing process had demonstrated acceptable control.
| Property | Value |
|---|---|
| Molecular Formula | C₂₇H₂₇F₂N₅O₃ |
| Molecular Weight | 507.54 g/mol |
| Exact Mass | ~507.2218 Da |
| H-Bond Donors | 3 |
| H-Bond Acceptors | 8 |
| Rotatable Bonds | 10 |
| TPSA | ~115 Ų |
| Formal Charge | 0 |
| Physical Form | White to pale yellow powder |
| Water Solubility | Practically insoluble according to FDA labeling |
| Stereocenters | 0 |
FDA describes remibrutinib as a white to pale yellow powder that is practically insoluble in water.
The FDA review further describes remibrutinib as a weak base with high permeability and low solubility at physiological pH and classifies it as BCS Class 2.
The active substance is packaged in a pharmaceutical-grade containment system. The EMA assessment describes LDPE bags placed inside triple-laminated foil bags, with the bags stored in drums for handling and transportation.
For the marketed finished product, FDA specifies storage at 20°C to 25°C, with excursions permitted between 15°C and 30°C. The product should remain in its original packaging to protect it from moisture.
Bulk API storage should follow the validated API stability program and approved storage specification.
Typical documentation for pharmaceutical-grade Remibrutinib API may include:
A qualified Remibrutinib API manufacturing program should emphasize controlled chemical synthesis, impurity management and consistent solid-state quality.
Important quality considerations include:
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 0.5% |
| Residue on Ignition | NMT 0.1% |
| Heavy Metals | NMT 20 ppm |
| Individual Impurity | NMT 0.10% |
| Total Impurities | NMT 0.50% |
| Water Content | NMT 1.0% |