Tofacitinib citrate – also known as CP-690550 and PF-04524477 – is an orally bioavailable inhibitor of the Janus kinase (JAK) family developed by Pfizer. JAK3 is a hematopoietic cell-restricted tyrosine kinase regulating lymphocyte survival, proliferation, and apoptosis via intracellular signaling. The citrate salt form carries CAS 540737-29-9; Tofacitinib citrate molecular weight is 504.5 g/mol. The Tofacitinib citrate structure is built around a pyrrolopyrimidine core; the full Tofacitinib citrate chemical structure includes a piperidine-nitrile side chain optimized for ATP-competitive JAK binding with oral activity.
Application of Tofacitinib citrate
Tofacitinib citrate is applied in research on immune cell signaling, cytokine-mediated inflammation, and autoimmune disease mechanisms. For such applications, a minimum purity of ≥98% by HPLC and adequate solubility in DMSO at concentrations suitable for standard in vitro workflows are required. Our product Tofacitinib citrate CAS no 540737-29-9 meets all these requirements and is available from stock for immediate use in research applications.
In Vitro
In vitro, Tofacitinib inhibits JAK1/JAK3 enzymatic activity with IC50 values of approximately 1–2 nM and 1 nM respectively, while showing weaker inhibition of JAK2 in the 20–100 nM range, thereby blocking γc cytokine-mediated STAT phosphorylation – including IL-2, IL-4, IL-15, IL-21 – in human T cells. This isoform preference reflects a mechanistic logic: JAK3 pairs exclusively with JAK1 in heterodimeric receptors for common γc cytokines, so the compound selectively suppresses a defined cytokine receptor subset. In endothelial cell assays, Tofacitinib also inhibits tube formation and migration in response to VEGF stimulation.
In Vivo
Oral administration in murine collagen-induced arthritis reduces paw swelling and joint damage at 1.5–15 mg/kg twice daily, correlating with decreased cytokines and STAT activation in synovial tissue. Anti-inflammatory effects are also documented in rodent models of transplant rejection and colitis. PK/PD studies using cytokine-induced STAT phosphorylation as a whole-blood readout confirmed predictable dose-exposure relationships – the basis for translating murine CIA findings to clinical dose selection in RA. Researchers planning to buy Tofacitinib citrate online should prioritize products supported by published PK/PD and efficacy data relevant to their intended research applications.
Biochemical and Physiological Actions
Tofacitinib citrate inhibits signaling through heterodimeric receptors associated with JAK3 and JAK1 with functional selectivity over JAK2-paired receptors. Downstream STAT blockade suppresses IL-2, IL-4, IL-7, IL-9, IL-15 and IL-21 – cytokines integral to lymphocyte activation, function, and proliferation. Reduced STAT-1 and STAT-3 phosphorylation inhibits Th1 and Th17 differentiation while producing a dose-dependent B cell count increase consistent with JAK3-deficiency phenotypes.
Features and Benefits of Tofacitinib citrate
The compound combines oral bioavailability, sub-nanomolar JAK3 potency, and a validated STAT-based pharmacodynamic readout. Its selectivity has been profiled across 30+ kinases with IC50 values exceeding 3000 nM outside the JAK family. Laboratories that buy Tofacitinib citrate from a reliable Tofacitinib citrate supplier should prioritize compounds supported by cross-validated data spanning enzyme assays, cellular models, and in vivo systems, making this compound the reference standard against which newer JAK inhibitors are benchmarked. For researchers searching for Tofacitinib citrate buy online, documented selectivity across the JAK family should remain the primary quality criterion when evaluating available products.
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