Ruxolitinib Phosphate is a pharmaceutical active pharmaceutical ingredient belonging to the Janus kinase inhibitor class. It is the phosphate salt of Ruxolitinib and is used in pharmaceutical formulations for conditions involving abnormal Janus kinase signalling. Ruxolitinib selectively inhibits JAK1 and JAK2, enzymes involved in signalling pathways associated with cytokines and growth factors that regulate hematopoiesis and immune function.
Ruxolitinib Phosphate has the molecular formula C₁₇H₂₁N₆O₄P and molecular weight 404.36 g/mol. Its primary CAS Number is 1092939-17-7. It is also known as Ruxolitinib Monophosphate and INCB018424 Phosphate. PubChem identifies Ruxolitinib Phosphate as the phosphate salt obtained by combining Ruxolitinib with one equivalent of phosphoric acid.
The FDA describes Ruxolitinib Phosphate as a white to off-white to light pink powder. It is soluble in aqueous buffers across a pH range of 1 to 8. FDA chemistry-review information further describes the drug substance as non-hygroscopic and reports pH-dependent aqueous solubility, with greater solubility under acidic conditions.
Ruxolitinib is the active moiety of Ruxolitinib Phosphate and belongs to the pyrrolopyrimidine-containing JAK inhibitor group. The molecule contains a defined R stereochemical configuration, which is part of its chemical identity. The phosphate salt is used in pharmaceutical products rather than the free base in several marketed formulations.
The FDA-approved chemical name is (R)-3-(4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1H-pyrazol-1-yl)-3-cyclopentylpropanenitrile phosphate. The FDA lists the molecular weight of the phosphate salt as 404.36 g/mol compared with 306.37 g/mol for the free base.
Ruxolitinib Phosphate is used in pharmaceutical products for the treatment of several diseases involving JAK-mediated signalling. The EMA identifies Ruxolitinib Phosphate as the active substance in Jakavi. Jakavi is indicated for myelofibrosis and polycythaemia vera and is also authorised for acute and chronic graft-versus-host disease in specified patient populations.
Ruxolitinib Phosphate is also used in topical pharmaceutical formulations. The FDA identifies Ruxolitinib Phosphate as the drug substance in Opzelura, a topical ruxolitinib product.
Quality control of Ruxolitinib Phosphate API requires appropriate identity, assay, related-substance, residual-solvent, water and inorganic-residue testing according to the approved API specification.
Identity may be established using techniques such as IR spectroscopy, HPLC retention time, LC-MS and other validated analytical procedures. Assay and related substances are generally evaluated using validated chromatographic methods.
Because a current authoritative public pharmacopoeial numerical specification could not be reliably verified for every CMS field, numerical limits should not be copied from unrelated commercial listings and represented as USP/Ph. Eur. requirements. The actual approved specification, DMF/CEP/ASMF or customer specification should govern release criteria.
Ruxolitinib Phosphate is a specialized pharmaceutical API relevant to oncology, hematology and dermatology formulations. Pharmaceutical manufacturers may require controlled API quality, batch-to-batch consistency and comprehensive analytical documentation for formulation development and commercial manufacturing.
Typical documentation may include a Certificate of Analysis (CoA), specification sheet, Safety Data Sheet (SDS/MSDS), Certificate of Origin, residual-solvent information and applicable regulatory documentation, depending on customer and destination-market requirements.
Ruxolitinib Phosphate should be stored according to the approved drug-substance stability specification and protected against inappropriate environmental exposure. The exact API storage condition should be based on validated stability data rather than automatically copying the finished-product storage condition.
Ruxolitinib Phosphate is an established JAK1/JAK2 inhibitor with pharmaceutical applications across myelofibrosis, polycythaemia vera, graft-versus-host disease and topical inflammatory skin indications. Consistent control of identity, assay, related substances, stereochemical purity and physical properties is essential for reliable pharmaceutical manufacturing.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |