ALK4 (IC50 = 1 μM); ALK5 (IC50 = 0.75 μM); ALK7 (IC50 = 2 μM)

ALK4, ALK5, and ALK7 activities can be inhibited by SB-431542, with IC50 values of 1 μM, 0.75 μM, and 2 μM, respectively [1]. ALK5, the lymph node type I receptor ALK7, and the activin type I receptor ALK4—all of which are closely linked to ALK5 in the kinase domain—are all inhibited by SB-431542 (0–10 μM; 24 hours) [1]. SB-431542 (0.1, 0.5, 1, 5, or 10 μM; 30 minutes) suppresses TGF-β and activin-induced Smad phosphorylation potently, but not BMP4 [1]. TGF-β-induced transcription, gene expression, apoptosis, and growth inhibition are all inhibited by SB-431542 (0–10 μM) [2].

In New Zealand rabbits, SB-431542 (subconjunctival; 0.5 and 2 mM; days 1, 2, 3, and 7) prevents scarring following glaucoma filtration surgery [3].

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In comparison with the control rabbits, the IOPs in the experimental groups remained at lower levels until day 25 (P<0.05) after the surgery. Histologic profiles showed that there was only a mild deposition of collagen in the subconjunctival space in the experimental groups. The cell growth and migration were inhibited effectively by SB-431542, regardless of whether TGF-beta was present in the culture system. SB-431542 abrogated TGF-beta-induced upregulation of alpha-SM-actin, CTGF, and Col I. It effectively inhibited the phosphorylation of Smad2 stimulated by TGF-beta but not that of the components of the MAPK pathways. Conclusions: SB-431542 inhibits scar formation after glaucoma filtration surgery. The mechanism may be that SB-431542 interferes in the phosphorylation of Smad2, thus abrogating TGF-beta-induced fibroblast transdifferentiation and then decreasing Col I synthesis.[3]

Small molecule inhibitors have proven extremely useful for investigating signal transduction pathways and have the potential for development into therapeutics for inhibiting signal transduction pathways whose activities contribute to human diseases. Transforming growth factor beta (TGF-beta) is a member of a large family of pleiotropic cytokines that are involved in many biological processes, including growth control, differentiation, migration, cell survival, adhesion, and specification of developmental fate, in both normal and diseased states. TGF-beta superfamily members signal through a receptor complex comprising a type II and type I receptor, both serine/threonine kinases. Here, we characterize a small molecule inhibitor (SB-431542) that was identified as an inhibitor of activin receptor-like kinase (ALK)5 (the TGF-beta type I receptor). We demonstrate that it inhibits ALK5 and also the activin type I receptor ALK4 and the nodal type I receptor ALK7, which are very highly related to ALK5 in their kinase domains. It has no effect on the other, more divergent ALK family members that recognize bone morphogenetic proteins (BMPs). Consistent with this, we demonstrate that SB-431542 is a selective inhibitor of endogenous activin and TGF-beta signaling but has no effect on BMP signaling. To demonstrate the specificity of SB-431542, we tested its effect on several other signal transduction pathways whose activities depend on the concerted activation of multiple kinases. SB-431542 has no effect on components of the ERK, JNK, or p38 MAP kinase pathways or on components of the signaling pathways activated in response to serum[1].

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Transcriptional Response Assay[2]
FET cells were transiently transfected with CMV-βgal, and p3TP-Lux or (CAGA)9MLP-Luc reporter plasmids. HepG2 cells were transiently transfected with CMV-βgal, and p21-Luc or PAI-1-Luc plasmids. Transfected cells were incubated in 0.2% FBS with 5 ng/ml TGF-β1 in the presence of SB-431542 for 22 hours. Cell lysates were used to measure both luciferase and β-gal activities, and the normalized luciferase activity was presented.[2]

Western Blot Analysis[1]
Cell Types: NIH 3T3 cells; HaCaT, NIH 3T3, C2C12 cells and T47D cells
Tested Concentrations: 10 μM; 0.1, 0.5, 1, 5, or 10 μM
Incubation Duration: 24 h; 30 min
Experimental Results: Inhibited efficiently phosphorylated Smad2. Inhibited the TGF-β- and activin-induced phosphorylation of Smad2 but not BMP-induced phosphorylation of Smad1.

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Apoptosis Analysis[2]
Cell Types: A549 and HT29 cells
Tested Concentrations: 10 μM
Incubation Duration: 24 h
Experimental Results: Inhibited TGF-induced growth suppression and apoptosis. Cell Invasion Assay[2]
Cell Types: A549 cells
Tested Concentrations: 2, 10 μM
Incubation Duration: 21 h
Experimental Results: Blocked TGF-induced tumor cell invasion.

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Cell Migration Assay [2]
Cell Types: A549 cells
Tested Concentrations: 2, 10 μM
Incubation Duration: 5 h, 30 h
Experimental Results: Blocked TGF-induced tumor cell migration.

Animal/Disease Models: Rabbits (3 to 5 months, 1.8 - 2.5 kg)[3]
Doses: 0.5 and 2 mM
Route of Administration: Subconjunctival injection, on days 1, 2, 3, and 7
Experimental Results: demonstrated wound healing and less severe scar formation.

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To explore the inhibitive effect of SB-431542 (an ALK5 inhibitor) on scar formation after glaucoma surgery and to identify the potential pharmacologic target(s). Methods: Twenty-four New Zealand rabbits underwent filtration surgery on the right eye and were divided into a control group and three experimental groups (n=6). Human Tenon's fibroblast monolayer was scraped to generate a single gap, and then the control medium with SB-431542 only or containing 10 microg/L TGF-beta1 and SB-431542 (1-20 microM) was added. The cells were pretreated with SB-431542 or in control medium for 30 minutes before induction with 10 microg/L TGF-beta1 or 1 microg/L TGF-beta2. The expression of alpha-SM-actin, CTGF, and Col I, as well as changes in the Smad, ERK, P38, and AKT signaling pathways were detected.[3]

[1]. Gareth J Inman, et al. SB-431542 is a potent and specific inhibitor of transforming growth factor-beta superfamily type I activin receptor-like kinase (ALK) receptors ALK4, ALK5, and ALK7. Mol Pharmacol. 2002 Jul;62(1):65-74.
[2]. Sunil K Halder, et al. A specific inhibitor of TGF-beta receptor kinase, SB-431542, as a potent antitumor agent for human cancers. Neoplasia. 2005 May;7(5):509-21.
[3]. Yi-qin Xiao, et al. SB-431542 inhibition of scar formation after filtration surgery and its potential mechanism. Invest Ophthalmol Vis Sci. 2009 Apr;50(4):1698-706.

SB 431542 is a member of the class of benzamides that is 4-(imidazol-2-yl)benzamide carrying additional 1,3-benzodioxol-5-yl and pyridin-2-yl substituents at positions 4 and 5 respectively on the imidazole ring. It has a role as an EC 2.7.10.1 (receptor protein-tyrosine kinase) inhibitor. It is a member of benzamides, a member of imidazoles, a member of pyridines and a member of benzodioxoles.

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Small molecule inhibitors have proven extremely useful for investigating signal transduction pathways and have the potential for development into therapeutics for inhibiting signal transduction pathways whose activities contribute to human diseases. Transforming growth factor beta (TGF-beta) is a member of a large family of pleiotropic cytokines that are involved in many biological processes, including growth control, differentiation, migration, cell survival, adhesion, and specification of developmental fate, in both normal and diseased states. TGF-beta superfamily members signal through a receptor complex comprising a type II and type I receptor, both serine/threonine kinases. Here, we characterize a small molecule inhibitor (SB-431542) that was identified as an inhibitor of activin receptor-like kinase (ALK)5 (the TGF-beta type I receptor). We demonstrate that it inhibits ALK5 and also the activin type I receptor ALK4 and the nodal type I receptor ALK7, which are very highly related to ALK5 in their kinase domains. It has no effect on the other, more divergent ALK family members that recognize bone morphogenetic proteins (BMPs). Consistent with this, we demonstrate that SB-431542 is a selective inhibitor of endogenous activin and TGF-beta signaling but has no effect on BMP signaling. To demonstrate the specificity of SB-431542, we tested its effect on several other signal transduction pathways whose activities depend on the concerted activation of multiple kinases. SB-431542 has no effect on components of the ERK, JNK, or p38 MAP kinase pathways or on components of the signaling pathways activated in response to serum.[1]

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Small molecule inhibitors of signaling pathways have proven to be extremely useful for the development of therapeutic strategies for human cancers. Blocking the tumor-promoting effects of transforming growth factor-beta (TGF-beta) in advanced stage carcinogenesis provides a potentially interesting drug target for therapeutic intervention. Although very few TGF-beta receptor kinase inhibitors (TRKI) are now emerging in preclinical studies, nothing is known about how these inhibitors might regulate the tumor-suppressive or tumor-promoting effects of TGF-beta, or when these inhibitors might be useful for treatment during cancer progression. We have investigated the potential of TRKI in new therapeutic approaches in preclinical models. Here, we demonstrate that the TRKI, SB-431542, inhibits TGF-beta-induced transcription, gene expression, apoptosis, and growth suppression. We have observed that SB-431542 attenuates the tumor-promoting effects of TGF-beta, including TGF-beta-induced EMT, cell motility, migration and invasion, and vascular endothelial growth factor secretion in human cancer cell lines. Interestingly, SB-431542 induces anchorage independent growth of cells that are growth-inhibited by TGF-beta, whereas it reduces colony formation by cells that are growth-promoted by TGF-beta. However, SB-431542 has no effect on a cell line that failed to respond to TGF-beta. This represents a novel potential application of these inhibitors as therapeutic agents for human cancers with the goal of blocking tumor invasion, angiogenesis, and metastasis, when tumors are refractory to TGF-beta-induced tumor-suppressor functions but responsive to tumor-promoting effects of TGF-beta.[2]

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Purpose: To explore the inhibitive effect of SB-431542 (an ALK5 inhibitor) on scar formation after glaucoma surgery and to identify the potential pharmacologic target(s). Methods: Twenty-four New Zealand rabbits underwent filtration surgery on the right eye and were divided into a control group and three experimental groups (n=6). Human Tenon's fibroblast monolayer was scraped to generate a single gap, and then the control medium with SB-431542 only or containing 10 microg/L TGF-beta1 and SB-431542 (1-20 microM) was added. The cells were pretreated with SB-431542 or in control medium for 30 minutes before induction with 10 microg/L TGF-beta1 or 1 microg/L TGF-beta2. The expression of alpha-SM-actin, CTGF, and Col I, as well as changes in the Smad, ERK, P38, and AKT signaling pathways were detected. Results: In comparison with the control rabbits, the IOPs in the experimental groups remained at lower levels until day 25 (P<0.05) after the surgery. Histologic profiles showed that there was only a mild deposition of collagen in the subconjunctival space in the experimental groups. The cell growth and migration were inhibited effectively by SB-431542, regardless of whether TGF-beta was present in the culture system. SB-431542 abrogated TGF-beta-induced upregulation of alpha-SM-actin, CTGF, and Col I. It effectively inhibited the phosphorylation of Smad2 stimulated by TGF-beta but not that of the components of the MAPK pathways. Conclusions: SB-431542 inhibits scar formation after glaucoma filtration surgery. The mechanism may be that SB-431542 interferes in the phosphorylation of Smad2, thus abrogating TGF-beta-induced fibroblast transdifferentiation and then decreasing Col I synthesis.[3]

C22H16N4O3

384.39

384.122

C, 68.74; H, 4.20; N, 14.58; O, 12.49

301836-41-9

SB-431542 (GMP);301836-41-9

4521392

Off-white to yellow solid powder

1.4±0.1 g/cm3

662.4±55.0 °C at 760 mmHg

214 °C(dec.)

354.4±31.5 °C

0.0±2.0 mmHg at 25°C

1.680

4.28

2

5

4

29

582

0

FHYUGAJXYORMHI-UHFFFAOYSA-N

InChI=1S/C22H16N4O3/c23-21(27)13-4-6-14(7-5-13)22-25-19(20(26-22)16-3-1-2-10-24-16)15-8-9-17-18(11-15)29-12-28-17/h1-11H,12H2,(H2,23,27)(H,25,26)

4-[4-(1,3-benzodioxol-5-yl)-5-pyridin-2-yl-1H-imidazol-2-yl]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: ≥ 2.08 mg/mL (5.41 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 20.8 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: ≥ 2.08 mg/mL (5.41 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in 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 20.8 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% DMSO+30% PEG 300+ddH2O: 5mg/mL

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