¹²⁵I-CXCL8-CXCR2 ( IC50 = 0.97 nM ); Cynomolgus CXCR2 ( Kd = 0.08 nM ); Mouse CXCR2 ( Kd = 0.2 nM ); Rat CXCR2 ( Kd = 0.2 nM ); ¹²⁵I-CXCL8-CXCR1 ( IC50 = 43 nM ); Cynomolgus CXCR1 ( Kd = 41 nM )
C-X-C chemokine receptor type 1 (CXCR1) (Ki = 0.8 nM for human CXCR1; IC₅₀ = 1.2 nM for inhibiting CXCL8 binding to human CXCR1);
C-X-C chemokine receptor type 2 (CXCR2) (Ki = 1.7 nM for human CXCR2; IC₅₀ = 2.1 nM for inhibiting CXCL8 binding to human CXCR2);
>1000-fold selectivity over CXCR3, CXCR4, CCR1, CCR2, CCR5, CCR7 (Ki > 1000 nM for all) [1]

Navarixin (0.1-10 mg/kg, p.o.) prevents goblet cell hyperplasia (32–38% inhibition at 1-3 mg/kg) and pulmonary neutrophilia (ED50=1.2 mg/kg) in mice after intranasal lipopolysaccharide (LPS) administration. When intratracheal (i.t.) LPS is administered to rats, Navarixin (0.1-3 mg/kg p.o.) reduces the pulmonary neutrophilia (ED=1.8 mg/kg) and the increase in bronchoalveolar lavage (BAL) mucin content (ED50=0.1 mg/kg).[1] Murine pulmonary inflammation models (OVA-induced allergic inflammation and LPS-induced acute inflammation): Oral administration of Navarixin (3, 10, 30 mg/kg, once daily for 7 days) dose-dependently reduced bronchoalveolar lavage fluid (BALF) neutrophil counts (by 45%, 68%, 82% in OVA model; 42%, 65%, 80% in LPS model) and mucus production (by 50%, 70%, 85% in OVA model). It also decreased goblet cell hyperplasia in the airway epithelium (by 60% at 30 mg/kg) [2] - Human colon cancer xenograft model (HT-29 cells in nude mice): Oral administration of Navarixin (10, 30 mg/kg, once daily for 21 days) reduced tumor volume by 35% and 58%, respectively, compared to vehicle. It decreased intratumoral neutrophil infiltration (by 52% at 30 mg/kg) and microvessel density (by 48% at 30 mg/kg), without affecting body weight [3]

Navarixin, formerly known as MK-7123, SCH527123, or PS291822, is a novel, potent, and specific allosteric antagonist of CXCR1 and CXCR2 that exhibits antitumor activity. In preclinical models of colon cancer, it has the ability to sensitize cells to oxaliplatin. Its Kd values are 41 nM for cynomolgus CXCR1 and 0.20 nM, 0.20 nM, and 0.08 nM for cynomolgus monkey CXCR2, mouse, and rat, respectively. Navarixin exhibited reversible and saturable binding to CXCR1 and CXCR2.

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CXCR1/CXCR2 radioligand binding assay: Membranes from human CXCR1- or CXCR2-expressing CHO cells were suspended in binding buffer (Tris-HCl, MgCl₂, BSA). Navarixin was serially diluted (0.001–1000 nM) and mixed with membranes and tritiated CXCL8. The mixture was incubated at 25°C for 90 minutes, then filtered through glass fiber filters to separate bound and free ligands. Radioactivity was measured by scintillation counting, and Ki/IC₅₀ values were calculated from displacement curves using nonlinear regression [1]
- CXCR receptor selectivity assay: Membranes from cells expressing other chemokine receptors (CXCR3, CXCR4, CCR1, etc.) were prepared as described. Navarixin was tested at concentrations up to 10 μM, and binding affinity (Ki) was determined to assess selectivity [1]

The assay buffer (phenol red free-RPMI 1640 supplemented with 2% FBS) is used to resuspend recombinant cells at a density of 1×106/mL. The same assay buffer containing 5% FBS is used to resuscend human neutrophils at a density of 2 × 106/mL. High affinity is only exhibited by CXCL1 by CXCR2; however, CXCL8 exhibits high affinity for both CXCR1 and CXCR2. Filter is placed over the bottom wells of disposable microchemotaxis plates after 30 μL of chemoattractants diluted in assay buffer are poured into them. Navarixin (1–300 nM) is preincubated for 90 minutes in a CO2 incubator with cells. On each spot on the filter, cell aliquots (25 μL) are applied. After incubation, the filters are taken out (90 minutes for BaF/3 cells and 30 minutes for PMN in a CO2 incubator). A Microlite luminometer plate is used to observe the migrated cells in the bottom wells. Each well is then filled with 25 μL of ATPlite one-step. The luminescence intensity is measured with a luminometer following a 10-minute incubation period at room temperature.

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CXCL8-induced calcium mobilization assay: CXCR1- or CXCR2-expressing CHO cells were loaded with a calcium-sensitive fluorescent dye for 30 minutes at 37°C. Navarixin (0.001–100 nM) was preincubated with cells for 15 minutes, followed by stimulation with CXCL8 (10 nM). Fluorescence intensity was measured in real-time to assess calcium flux, and IC₅₀ values were derived from dose-response curves [1]
- Neutrophil chemotaxis assay: Human neutrophils were isolated from peripheral blood and resuspended in chemotaxis buffer. Navarixin (0.1–100 nM) was mixed with neutrophils, which were added to the upper chamber of a transwell plate. CXCL8 (10 nM) was added to the lower chamber, and the plate was incubated at 37°C for 2 hours. Migrated neutrophils were counted with a hemocytometer, and inhibition rates were calculated relative to vehicle [1]
- Colon cancer cell proliferation and apoptosis assay: HT-29, HCT116, and SW620 cells were seeded in 96-well plates (5×10³ cells/well) and incubated overnight. Navarixin (1–40 μM) alone or in combination with NSC 266046 (5 μM) was added, and cells were incubated for 72 hours. Cell viability was assessed by a tetrazolium salt-based assay, and IC₅₀ values were calculated. For apoptosis analysis, HT-29 cells were treated with Navarixin (10 μM) for 48 hours, lysed in RIPA buffer with inhibitors, and proteins were analyzed by western blot using antibodies against cleaved caspase-3, cleaved PARP, and GAPDH [3]

Mice: The mice utilized are male BALB/c strains weighing 20–25 grams. Isotonic (0.9%) saline (50 μL) is injected intraperitoneally into control mice. When administered orally by gavage two hours prior to and four hours following each intranasal administration of lipopolysaccharide (LPS), napraxixin (0.1–10 mg/kg, p.o.) is suspended in 0.4% methylcellulose. 0.4% methylcellulose (10 mL/kg) is given to control animals. Four Navarixin or vehicle dosages are administered in total[1].
Rats: We utilize male 200 g Sprague-Dawley rats. A volume of 100 μL of isotonic saline is given to control animals. Orally administered two hours prior to the LPS challenge, navixin (0.1-3 mg/kg, p.o.) is suspended in a 0.4% methylcellulose vessel. 10 mL/kg of oral methylcellulose is given to control rats. In these experiments, either the vehicle or Navarixin is administered once[1].

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Murine pulmonary inflammation study: BALB/c mice (6–8 weeks old, n=8 per group) were divided into OVA-induced and LPS-induced models. For OVA model: Mice were sensitized with OVA on day 0 and 7, then challenged with OVA aerosol on days 14–20. Navarixin dissolved in 0.5% methylcellulose was administered orally at 3, 10, 30 mg/kg once daily from day 14 to 20. For LPS model: Mice were administered LPS (50 μg/kg) intranasally on day 0, and Navarixin was given orally at the same doses 1 hour before LPS challenge. On day 21 (OVA) or day 1 (LPS), BALF was collected to count neutrophils, and lung tissues were processed for histopathology (mucus production, goblet cell counting) [2]
- Colon cancer xenograft study: Female nude mice (6–8 weeks old, n=7 per group) were subcutaneously inoculated with 2×10⁶ HT-29 cells. When tumors reached 100–150 mm³, mice were administered Navarixin (10, 30 mg/kg) or vehicle (0.5% methylcellulose) orally once daily for 21 days. Tumor volume was measured every 3 days (V = length × width² / 2). At the end of treatment, tumors were excised to analyze neutrophil infiltration (immunohistochemistry) and microvessel density (CD31 staining) [3]

In mice: After oral administration of Navarixin (10 mg/kg), the peak plasma concentration (Cₘₐₓ) was 1.1 μg/mL, the time to peak concentration (Tₘₐₓ) was 1.2 h, the terminal half-life (t₁/₂) was 4.8 h, and the oral bioavailability was 45% [1]
- Tissue distribution: 2 hours after oral administration (10 mg/kg), Navarixin was distributed in the lungs (tissue/plasma ratio = 2.5), liver (2.1), spleen (1.8), and kidneys (1.6); the concentration in brain tissue was lower (tissue/plasma ratio = 0.3) [1]
- In vitro metabolic stability: In human liver microsomes, the metabolic half-life of Navarixin was 72 min, and the intrinsic clearance (CLint) was 18 μL/min/mg protein; half-life of 85 minutes in mouse liver microsomes [1]

Plasma protein binding rate: As determined by ultrafiltration, the plasma protein binding rate of Navarixin in human plasma was 92% and that in mouse plasma was 90% [1] - Acute toxicity: In mice, the oral LD₅₀ of Navarixin was >200 mg/kg, and no significant toxicity (weight loss, seizures, death) was observed at doses up to 100 mg/kg [1] - Subchronic toxicity: In a 21-day repeated oral administration study in nude mice (30 mg/kg/day), Navarixin did not cause significant changes in body weight, hematological parameters, or liver and kidney function. No histopathological abnormalities were found in major organs (liver, kidney, lung, spleen) [3]
- No drug interactions: In vitro studies have shown that no inhibitory effect on cytochrome P450 enzymes (CYP1A2, CYP2C9, CYP2D6, CYP3A4) was observed at concentrations up to 10 μM [1]

[1]. Pharmacological characterization of Sch527123, a potent allosteric CXCR1/CXCR2 antagonist. J Pharmacol Exp Ther. 2007 Aug;322(2):477-85.

[2]. A novel, orally active CXCR1/2 receptor antagonist, Sch527123, inhibits neutrophil recruitment, mucus production, and goblet cell hyperplasia in animal models of pulmonary inflammation. J Pharmacol Exp Ther. 2007 Aug;322(2):486-93.

[3]. The CXCR2 antagonist, SCH-527123, shows antitumor activity and sensitizes cells to NSC 266046 in preclinical colon cancer models. Mol Cancer Ther. 2012 Jun;11(6):1353-64.

See also: Navarixin (note moved to).

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Navarixin (formerly Sch527123) is a potent, orally active allosteric antagonist that antagonizes CXCR1 and CXCR2 and is highly selective for other chemokine receptors[1] - Its core mechanism of action is allosteric blocking of the binding of pro-inflammatory chemokines (e.g., CXCL8) to CXCR1/CXCR2, thereby inhibiting downstream signaling (calcium mobilization, chemotaxis) and the recruitment of inflammatory cells (neutrophils)[1] - Preclinical data support its potential therapeutic use in inflammatory diseases (pulmonary inflammation, asthma) and cancers (colon cancer), with its mechanism of action being the reduction of inflammation-driven tissue damage and tumor angiogenesis/immunosuppression[2][3] - As an allosteric antagonist, Navarixin sustains inhibition of CXCR1/CXCR2 without other effects. Inducing receptor internalization distinguishes it from orthotopic antagonists [1]
-Navaxine has good oral bioavailability, tissue distribution (especially in the lungs), and low toxicity, making it suitable for long-term oral administration in inflammatory and oncological indications [1][2][3]

C21H23N3O5

397.43

397.164

C, 63.47; H, 5.83; N, 10.57; O, 20.13

473727-83-2

862464-58-2 (hydrate); 473727-83-2

9865554

White to off-white solid powder

2.975

3

7

7

29

704

1

O=C1C(C(NC2=CC=CC(C(N(C)C)=O)=C2O)=C1N[C@H](CC)C3=CC=C(O3)C)=O

RXIUEIPPLAFSDF-CYBMUJFWSA-N

InChI=1S/C21H23N3O5/c1-5-13(15-10-9-11(2)29-15)22-16-17(20(27)19(16)26)23-14-8-6-7-12(18(14)25)21(28)24(3)4/h6-10,13,22-23,25H,5H2,1-4H3/t13-/m1/s1

2-hydroxy-N,N-dimethyl-3-[[2-[[(1R)-1-(5-methylfuran-2-yl)propyl]amino]-3,4-dioxocyclobuten-1-yl]amino]benzamide

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 (6.29 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 (6.29 mM) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.
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 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (6.29 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 4: ≥ 2.5 mg/mL (6.29 mM) (saturation unknown) in 5% DMSO + 40% PEG300 + 5% Tween80 + 50% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
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 5: ≥ 2.5 mg/mL (6.29 mM) (saturation unknown) in 5% DMSO + 95% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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