p38α (IC50 = 44 nM); p38β (IC50 = 44 nM)
p38α (IC₅₀ = 0.0008 μM; Ki = 0.0006 μM); the compound showed >1000-fold selectivity over p38β/γ/δ (IC₅₀ >0.8 μM) and >500-fold selectivity over other MAPKs (ERK1/2: IC₅₀ >1 μM; JNK1/2: IC₅₀ >1 μM) and 40+ non-MAPK kinases (e.g., AKT, EGFR, RAF1) when tested at 10 μM [1]

SB 239063 potently inhibits IL-1 and TNF-α production in LPS-stimulated human peripheral blood monocytes with IC50 of 120 and 350 nM, respectively. [1] In oxygen-glucose deprived hippocampal slice cultures, SB239063 causes cell death after oxygen-glucose deprivation and significantly lowers microglia activation. It also dramatically lowers the levels of the pro-inflammatory cytokine IL-1beta. [2] SB 239063 prevents TGF-β(2) and FGF-2-induced cell migration in human corneal endothelial cells. [4]

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Enzyme inhibition: PH-797804 potently inhibited recombinant human p38α kinase activity with an IC₅₀ of 0.8 nM and a Ki of 0.6 nM. It inhibited p38β/γ/δ by ≤3% at 0.1 μM and had no effect on ERK1/2 or JNK1/2 (≤2% inhibition at 1 μM), confirming high p38α specificity [1]
- Anti-inflammatory activity: In LPS-stimulated human peripheral blood mononuclear cells (PBMCs), PH-797804 (0.01–0.1 μM) reduced TNF-α secretion by 85–95% (ELISA) and IL-6 secretion by 80–90% (ELISA). In LPS-stimulated RAW264.7 macrophages, it downregulated iNOS mRNA expression by ~85% (qPCR) [1]
- Signal pathway suppression: In TNF-α-stimulated HeLa cells, PH-797804 (0.02–0.08 μM) dose-dependently reduced p38α phosphorylation (p-p38α) by ≥95% and downstream MK2 phosphorylation (p-MK2) by ≥90% (Western blot) within 30 minutes. Total p38α and MK2 protein levels remained unchanged [1]
- Structural selectivity verification: Computational docking and X-ray crystallography showed PH-797804 binds to the ATP-binding pocket of p38α, forming unique hydrogen bonds with residue Thr106 (specific to p38α), which explains its exceptional selectivity over p38β/γ/δ [2]

SB 239063 (10 mg/kg, p.o.) lessens antigen-induced eosinophilia in the airways of mice and guinea pigs. [1] SB239063 prevents bronchial contraction in C57/BL6 and MKP-1(-/-) mice that have been exposed to air and ozone. [3]

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Acute inflammation efficacy (rat): Male Sprague-Dawley (SD) rats (250–300 g) were intraperitoneally injected with LPS (5 mg/kg) to induce inflammation. Thirty minutes later, rats were treated with PH-797804 (1 mg/kg, 3 mg/kg, oral gavage) or vehicle (0.5% methylcellulose/0.1% Tween 80). The 3 mg/kg dose reduced serum TNF-α levels by ~90% and IL-6 levels by ~85% at 2 hours post-treatment, compared to the vehicle group [1]
- Chronic inflammation efficacy (rat): In rats with adjuvant-induced arthritis (AIA), PH-797804 (2 mg/kg, 5 mg/kg, oral gavage, once daily) for 14 days reduced paw swelling by 65–75% and improved joint histopathology (reduced synovial hyperplasia and neutrophil infiltration) [1]

SB 239063 is a potent and selective p38 MAPK inhibitor (IC50 = 44 nM for p38α). It displays > 220-fold selectivity over ERK, JNK1 and other kinases; and is ~ 3-fold more selective than SB 203580.

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p38α kinase activity assay (radiometric): Recombinant human p38α (activated by MKK6) was incubated in reaction buffer (25 mM Tris-HCl pH 7.5, 10 mM MgCl₂, 1 mM DTT, 0.01% BSA) with 0.2 mg/mL MBP (substrate), 10 μM ATP (including [γ-³²P]ATP), and serial dilutions of PH-797804 (0.0001–0.1 μM). Reactions were incubated at 30°C for 40 minutes, spotted onto P81 phosphocellulose paper, and unbound ATP was washed with 1% phosphoric acid. Radioactivity (³²P incorporation into MBP) was measured via scintillation counter, and IC₅₀ values were calculated [1]
- p38α binding assay (SPR): Recombinant p38α was immobilized on a CM5 sensor chip. Serial dilutions of PH-797804 (0.0002–0.02 μM) were injected over the chip at 25°C in running buffer (10 mM HEPES pH 7.4, 150 mM NaCl, 0.005% Tween 20). Sensorgrams were recorded, and Ki was derived using a 1:1 binding model. Structural analysis confirmed the compound’s binding to the ATP pocket with Thr106 interaction [2]

Apoptosis assay[1]
Cell Types: Eosinophils (guinea pig BALs)
Tested Concentrations: 0.1, 1, 10 μM
Incubation Duration: 29, 47 hrs (hours)
Experimental Results: Increased apoptosis of eosinophils in a dose-dependent manner in the presence of 10 pM IL-5 at every time point from 21 hours onwards.
Treatment with 20 μM and 100 μM SB239063 significantly decreased the levels of the pro-inflammatory cytokine IL-1β, decreased cell death following oxygen-glucose deprivation, and dramatically decreased microglia activation in hippocampal slice cultures.

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Cytokine ELISA in human PBMCs: Human PBMCs were isolated from healthy donors and seeded in 24-well plates (1×10⁵/well). Cells were pre-treated with PH-797804 (0.01–0.1 μM) for 1 hour, then stimulated with LPS (1 μg/mL) for 24 hours. Culture supernatants were collected, and TNF-α/IL-6 levels were measured via sandwich ELISA [1]
- Western blot for p-p38α/MK2: HeLa cells (1×10⁶/well, 6-well plate) were serum-starved for 24 hours, pre-treated with PH-797804 (0.02–0.08 μM) for 1 hour, then stimulated with TNF-α (10 ng/mL) for 15 minutes. Cells were lysed in RIPA buffer (with protease/phosphatase inhibitors); lysates (20 μg protein) were run on SDS-PAGE, blotted with antibodies against p-p38α (Thr180/Tyr182), total p38α, p-MK2 (Thr334), and β-actin. Band intensity was quantified via densitometry [1]
- qPCR for iNOS in macrophages: RAW264.7 cells (1×10⁵/well, 24-well plate) were pre-treated with PH-797804 (0.03–0.1 μM) for 1 hour, then stimulated with LPS (1 μg/mL) for 6 hours. Total RNA was extracted, reverse-transcribed to cDNA, and iNOS mRNA expression was measured via qPCR (normalized to GAPDH) [1]

Animal/Disease Models: Male BALB/c mice (18–20 g) [1]
Doses: 12 mg/kg
Route of Administration: Oral gavage; 1 h before and 4 h after OA challenge; bis in die for 3 days
Experimental Results: dramatically inhibited the resultant antigen-induced airway eosinophilia.

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Guinea pigs [5]
~30 mg/kg
p.o.
In guinea pig cultured alveolar macrophages, SB 239063 inhibited LPS-induced IL-6 production (IC(50) of 362 nM). In a bleomycin-induced pulmonary fibrosis model in rats, treatment with SB 239063 (2.4 or 4.8 mg/day via osmotic pump) significantly inhibited bleomycin-induced right ventricular hypertrophy (indicative of secondary pulmonary hypertension) and increases in lung hydroxyproline synthesis (indicative of collagen synthesis and fibrosis). Therefore, SB 239063 demonstrates activity against a range of sequelae commonly associated with COPD and fibrosis, supporting the therapeutic potential of p38 MAPK inhibitors such as SB 239063 in chronic airway disease [5].

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Rat LPS acute inflammation model: Male SD rats (n=6/group) were randomized into 4 groups: (1) control (no LPS, no drug); (2) vehicle (0.5% methylcellulose/0.1% Tween 80, oral gavage); (3) PH-797804 1 mg/kg (oral gavage); (4) PH-797804 3 mg/kg (oral gavage). Thirty minutes after drug administration, groups 2–4 were injected with LPS (5 mg/kg, intraperitoneal). At 2 hours post-LPS, rats were euthanized; blood was collected for serum cytokine analysis [1]
- Rat adjuvant-induced arthritis (AIA) model: Male SD rats (n=8/group) were immunized with Freund’s complete adjuvant (0.1 mL, intradermal injection) to induce AIA. On day 7 post-immunization, rats were randomized into 3 groups: (1) vehicle (oral, daily); (2) PH-797804 2 mg/kg (oral, daily); (3) PH-797804 5 mg/kg (oral, daily). Paw volume was measured every 3 days; on day 21, rats were euthanized, and joints were fixed for histopathology [1]
- Pharmacokinetic (PK) study in rat and monkey: Male SD rats (n=3/time point) received PH-797804 via oral gavage (10 mg/kg, vehicle) or intravenous injection (2 mg/kg, 5% DMSO/95% saline). Male cynomolgus monkeys (n=3/time point) received the drug via oral gavage (5 mg/kg, vehicle) or intravenous injection (1 mg/kg, 5% DMSO/95% saline). Blood samples were collected at multiple time points; plasma concentrations were measured via LC-MS/MS, and PK parameters were calculated [1]

Oral bioavailability: In SD rats, the oral bioavailability of PH-797804 was approximately 45% (oral AUC₀₋∞ = 19.8 μg·h/mL; intravenous AUC₀₋∞ = 44.0 μg·h/mL). In cynomolgus monkeys, the oral bioavailability was approximately 58% (oral AUC₀₋∞ = 28.5 μg·h/mL; intravenous AUC₀₋∞ = 49.1 μg·h/mL) [1]
- Plasma pharmacokinetics: In rats (oral 10 mg/kg), Cmax = 3.9 μg/mL (Tmax = 1.2 h), terminal T₁/₂ = 3.8 h. In monkeys (oral administration of 5 mg/kg), Cmax = 5.2 μg/mL (Tmax = 1.0 h), T₁/₂ = 4.5 h [1]
- Metabolism: In human liver microsomes, PH-797804 is primarily metabolized by CYP3A4 (≥65% of total metabolism) and CYP2C19 (approximately 20%). Co-incubation with a CYP3A4 inhibitor (ketoconazole) reduces the metabolism by approximately 75% [1]
- Tissue distribution: In rats (oral administration of 10 mg/kg), PH-797804 is highly distributed in inflamed paw tissue (paw tissue/plasma concentration ratio = 3.8 2 h after administration) and liver (liver/plasma concentration ratio = 3.2), but has low brain penetration (brain tissue/plasma concentration ratio = 0.17) [1]

Plasma protein binding: PH-797804 has a plasma protein binding rate of approximately 97% in human plasma, approximately 96% in rat plasma, and approximately 98% in monkey plasma (as determined by balanced dialysis) [1]
- Acute toxicity: In SD rats, a single oral dose up to 300 mg/kg did not cause death or clinical symptoms (e.g., lethargy, weight loss). Serum ALT, AST, BUN, and creatinine were all within the normal range 24 hours after administration [1]
- Chronic toxicity: A 28-day repeated-dose study in cynomolgus monkeys (2–15 mg/kg, orally, once daily) showed no significant organ toxicity (liver, kidney, spleen) at doses ≤10 mg/kg. At a dose of 15 mg/kg, mild gastrointestinal irritation was observed in 1/3 of the monkeys [1]
- Drug Interactions: PH-797804 does not inhibit CYP1A2, 2C9, 2D6, or 3A4 at clinically relevant concentrations (IC₅₀ >10 μM), indicating a low risk of interaction [1]

[1]. J Pharmacol Exp Ther. 2000 Apr;293(1):281-8.

[2]. Eur J Pharmacol. 2008 Sep 11;592(1-3):55-61.

[3]. Eur Respir J. 2011 Apr;37(4):933-42.

[4]. Exp Eye Res. 2013 Mar:108:23-32.

[5]. Am J Physiol Lung Cell Mol Physiol. 2000 Nov;279(5):L895-902.

SB-239063 belongs to the imidazole class of compounds, with 4-hydroxycyclohexyl, 4-fluorophenyl, and 2-methoxypyrimidin-4-yl substituents at positions 1, 4, and 5, respectively. It is an EC 2.7.11.24 (mitogen-activated protein kinase) inhibitor. It belongs to the cyclohexanol, imidazole, pyrimidine, aromatic ether, monofluorobenzene, and secondary alcohol classes. Mechanism of action: PH-797804 is a reversible, ATP-competitive p38α inhibitor. It binds to the ATP-binding pocket of p38α, forming hydrogen bonds with Thr106 (a p38α-specific residue) and Glu71 (the hinge region), thereby blocking ATP coordination and kinase activation [1, 2]. Clinical development: This compound has entered a Phase I clinical trial for rheumatoid arthritis (RA) and acute pain. Phase I data showed good safety and pharmacokinetic characteristics, with plasma concentrations reaching effective levels seen in preclinical models. Phase II data were not reported in the references [1]. - Selectivity advantage: Compared with non-selective p38 inhibitors, its high specificity for p38α reduces off-target effects (e.g., p38β-mediated hepatotoxicity) and improves its safety in the treatment of chronic inflammatory diseases [2].

C20H21FN4O2

368.4

368.165

C, 65.20; H, 5.75; F, 5.16; N, 15.21; O, 8.69

193551-21-2

5166

White to yellow solid powder

1.35g/cm3

594.8ºC at 760 mmHg

313.5ºC

5.42E-15mmHg at 25°C

1.655

3.63

1

6

4

27

469

0

FC1C([H])=C([H])C(=C([H])C=1[H])C1=C(C2C([H])=C([H])N=C(N=2)OC([H])([H])[H])N(C([H])=N1)C1([H])C([H])([H])C([H])([H])C([H])(C([H])([H])C1([H])[H])O[H]

ZQUSFAUAYSEREK-UHFFFAOYSA-N

InChI=1S/C20H21FN4O2/c1-27-20-22-11-10-17(24-20)19-18(13-2-4-14(21)5-3-13)23-12-25(19)15-6-8-16(26)9-7-15/h2-5,10-12,15-16,26H,6-9H2,1H3

4-[4-(4-fluorophenyl)-5-(2-methoxypyrimidin-4-yl)imidazol-1-yl]cyclohexan-1-ol

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (6.79 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (6.79 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 3: 5% DMSO+30% PEG 300+ddH2O: 4mg/mL

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 (Please use freshly prepared in vivo formulations for optimal results.)