PF-06263276 is a pan-Janus kinase inhibitor from Pfizer, reported in 2017 as a clinical candidate for inhaled and topical use. Registered under CAS 1421502-62-6, it was meant to act where inflammation begins, in the airways or skin, not body-wide.
The molecular formula is C31H31FN8O2, the PF-06263276 molecular weight is 566.63 g/mol, and the calculated logP is near 4.4. PF-06263276 was optimized for inhaled and topical delivery by combining potent, sustained JAK inhibition with physicochemical and metabolic properties intended to limit systemic exposure after local administration. The PF-06263276 chemical structure is built on an indazole core, carrying a fluorinated, ethyl-substituted phenol on one side and a tetrahydroimidazopyridine with a piperidinyl-pyrazine carboxamide on the other. The PF-06263276 molecular structure supports ATP-competitive binding across the JAK family and extends into the kinase back pocket, a binding profile associated with potent pan-JAK inhibition and prolonged cellular activity. Catalogs list Pfizer PF-06263276 as PF06263276.
Application of PF-06263276
Researchers reach for this compound for one of two reasons: to silence every Janus kinase at once, or as a worked example of a drug engineered to stay put.
The first case matters because most JAK tools are selective by design. Blocking one isoform leaves the others free to carry signal through alternative pairings, which muddies the readout when several cytokines drive one phenotype. A pan-JAK inhibitor can help determine whether a phenotype depends on signaling shared across multiple JAK combinations. Persistence of the response after treatment should, however, be interpreted together with compound exposure and evidence of STAT pathway inhibition. That makes it a decisive control in cytokine-driven skin and airway models, and a natural counterpoint to a selective inhibitor when the question is which isoform matters.
The second case concerns delivery, not pharmacology. Local exposure with minimal systemic reach is the central problem in topical and inhaled anti-inflammatory work, and this molecule addresses it through physical chemistry, not formulation.
Stock solutions in DMSO reach roughly 33 mg/mL, and the powder ships at room temperature with no dangerous-goods limits. One caveat travels with it: because inhibition spans the family, no phenotype seen under treatment can be pinned on one kinase without further work.
In Vitro
In human whole blood, the compound suppresses STAT phosphorylation triggered by IFN-alpha, IL-23, IL-4, IL-6 and GM-CSF, with IC50 values from 0.62 to 5.2 microM. The lower apparent potency in human whole blood is consistent with the compound’s very high plasma protein binding and the additional permeability and signaling factors present in cellular assays compared with isolated kinase assays.
In Vivo
Two mouse models frame the intended routes. Dosed intratracheally from 0.3 to 100 microg per animal, PF-06263276 blocked IL-6-driven lung pSTAT3, with an ED50 near 3 microg. Applied topically as a 4% solution over 11 days, it cut ear swelling by 48% in IL-23-induced skin inflammation, suppressing JAK2 and TYK2 signalling.
Biochemical and Physiological Actions
Potency covers all four members: IC50 values of 2.2 nM for JAK1, 23.1 nM for JAK2, 59.9 nM for JAK3 and 29.7 nM for TYK2. Janus kinases sit beneath cytokine receptors in pairs and, once a ligand binds, phosphorylate each other and the STAT proteins carrying the signal onward. Because different cytokine receptors signal through distinct JAK pairings, inhibition of all four family members enables PF-06263276 to suppress multiple JAK/STAT pathways, although the extent of inhibition depends on compound concentration and the cytokine system being studied.
Features and Benefits of PF-06263276
The PF-06263276 structure was optimised for one job, and the profile reflects that:
- Single-digit nanomolar JAK1 potency, with real coverage of the other three.
- Physicochemistry tuned for local retention, not systemic circulation.
- Efficacy shown by inhaled and topical routes in mouse models.
- Room-temperature handling, no dangerous-goods surcharge.
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