IC50: 129 nM (ALK4), 47 nM (ALK5)
SB-505124 HCl targets activin receptor-like kinase 5 (ALK5), also known as TGF-β receptor type I (TGF-βRI), and ALK4. It is selective for ALK5 and ALK4 over a panel of 27 kinases at 10 µM. It selectively inhibits signaling from TGF-β and activin but does not affect BMP signaling (which activates ALK3 and ALK6).

At concentrations up to 100 μM for 48 hours, SB-505124 shows no toxicity to renal epithelial A498 cells. With an IC50 value of 129±11 nM, which is approximately 2.5 times less sensitive than ALK5, 505124 inhibits the closely related ALK4, but not ALK2, even at concentrations up to 10 μM. In all three of these cell lines, SB-505124 (1 μM) inhibits the TGF-β-induced phosphorylation of Smad2 in a concentration-dependent manner. Even though these cells exhibit distinct patterns of activation, SB-505124 (1 or 5 μM) effectively suppresses TGF-β-induced activation of JNK/SAP, extracellular signal-regulated kinase 1/2, and p38[1]. In vitro, SB-505124 (10 µM) inhibits the phosphorylation of Smad2, as well as the expression of CTGF and α-SMA. By using immunofluorescence, SB-505124 is able to suppress CTGF and α-SMA. While cell outgrowth is poor from eyes treated with MMC, it is robust from explants dissected from eyes to which SB-505124 is applied during GFS[3].

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The gel was characterized for in vitro drug release and viscosity studies. Cytotoxicity of Pluronic® F-127 was examined by MTT assay using cultured rabbit subconjunctival fibroblasts. The in vitro drug release study demonstrated 100% drug release within 12 h. The gel did not show cytotoxicity to the cultured rabbit subconjunctival cells by MTT assay. [2]
In vitro, SB-505124 HCl inhibits TGF-β and activin signaling. It is used as a tool to study the role of TGF-β signaling in various cellular processes, including cell growth, differentiation, and fibrosis. Its selectivity over other kinases makes it a valuable research tool.

In C57Bl6 mice bearing A549 xenografts, SB-505124 (5 mg/kg; i.p.) by itself showed no impact; however, when combined with a single carboplatin dose (60 mg/kg), SB-505124 caused long-lasting responses in five species, eliminating the need for maintenance therapy [4].

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The purpose of this study is to investigate a thermoreversible gel using Pluronic® F-127 to deliver an activin receptor-like kinase 5 (ALK-5) inhibitor SB-505124 in glaucoma filtration surgery (GFS). In addition, Pluronic® F-127 gel (18% w/v) containing 5 mg of SB-505124 was applied at the surgical site in an in vivo rabbit GFS model. In the in vitro viscosity study, the gel showed a change in viscosity (from 1000 cps to 45,000 cps) from low temperature (10°C) to body temperature (37°C). In the in vivo rabbit GFS model, the drug was successfully delivered by injection and no severe post-surgical complications were observed. A thermoreversible gel system with SB-505124 was successfully prepared and delivered for the rabbit GFS model, and it may provide a novel delivery system in GFS.[2]
In vivo, SB-505124 HCl is an orally available compound used in research models to study TGF-β signaling. It has been studied for its potential therapeutic applications in various diseases, including fibrosis and cancer. Its effects are measured by the inhibition of TGF-β-induced signaling and downstream effects.

Clinically, there is a great need for small molecule inhibitors that could control pathogenic effects of transforming growth factor (TGF-beta) and/or modulate effects of TGF-beta in normal responses. Inhibition of TGF-beta signaling would be predicted to enhance re-epithelialization of cutaneous wounds and reduce scarring fibrosis. Selective small molecule inhibitors of the TGF-beta signaling pathway developed for therapeutics will also be powerful tools in experimentally dissecting this complex pathway, especially its cross-talk with other signaling pathways. In this study, we characterized 2-(5-benzo[1,3]dioxol-5-yl-2-tert-butyl-3H-imidazol-4-yl)-6-methylpyridine hydrochloride (SB-505124), a member of a new class of small molecule inhibitors related to imidazole inhibitors of p38, which inhibit the TGF-beta type I receptor serine/threonine kinase known as activin receptor-like kinase (ALK) 5. We demonstrate that this compound selectively and concentration-dependently inhibits ALK4-, ALK5-, and ALK 7-dependent activation of downstream cytoplasmic signal transducers, Smad2 and Smad3, and of TGF-beta-induced mitogen-activated protein kinase pathway components but does not alter ALK1, ALK2, ALK3 or ALK6-induced Smad signaling. SB-505124 also blocks more complex endpoints of TGF-beta action, as evidenced by its ability to abrogate cell death caused by TGF-beta1 treatment. SB-505124 is three to five times more potent than a related ALK5 inhibitor described previously, SB-431542[1].
The in vitro enzyme inhibition assay for SB-505124 HCl involves measuring its ability to inhibit the kinase activity of ALK4 and ALK5. This is typically done using a kinase assay with a peptide substrate and ATP. The IC50 for each isoform is determined. Its selectivity is confirmed by screening against a panel of kinases.

Cell viability is measured as described previously or by using the modified tetrazolium salt WST-1. Approximately 2000 cells are seeded in 96-well dishes in 100 μL of 0.2% FBS phenol red-free media overnight. The cells are treated with 50 μL of SB-505124 (to achieve the final concentrations indicated) for 30 min before being treated with or without TGF-β1 and TNF-α to a final volume of 200 μL. Cell growth is measured at the indicated time points by incubating each well with 10 μL of WST-1 for 3 h at 37°C. Metabolically active cells cleave WST-1 to water-soluble formazan, which is directly quantitated with an enzyme-linked immunosorbent assay plate reader. Each experiment is done at least twice, and treatment for each cell line is done in triplicate.

Animal/Disease Models: C57Bl6 mice with A549 xenografts [4]
Doses: 5 mg/kg
Route of Administration: intraperitoneal (ip) injection; Daily
Experimental Results: No effect alone, but a single dose of carboplatin (60 mg/kg) gave The drug produced durable responses in 5 animals, requiring no maintenance treatment.

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In an in vivo rabbit GFS model, SB-505124 was delivered in a lactose tablet during surgery. Eyes were examined by slit-lamp and intraocular pressure (IOP) was measured until the time of bleb failure or up to 28 days after surgery. Tissue sections on day 5 after surgery were histologically evaluated after staining with hematoxylin and eosin. The sections were also immunostained for CTGF and α-SMA.[3]
In vivo animal experiments for SB-505124 HCl are conducted in models of fibrosis, cancer, and other TGF-β-related diseases. The compound is administered orally, and its effects on disease progression, tissue fibrosis, and TGF-β signaling are assessed.

SB-505124 HCl has been studied in preclinical models and has characterized pharmacokinetic properties. It is orally bioavailable. Its half-life and metabolism have been studied in animals. It is typically stored as a powder and is soluble in DMSO.

SB-505124 HCl is generally well-tolerated in animal studies. Its toxicity data are limited, as it is primarily a research compound. As with all research chemicals, standard laboratory safety practices should be followed.

[1]. SB-505124 is a selective inhibitor of transforming growth factor-beta type I receptors ALK4, ALK5, and ALK7. Mol Pharmacol. 2004 Mar;65(3):744-52.

[2]. Thermoreversible gel for delivery of receptor-like kinase 5 inhibitor SB-505124 for glaucoma filtration surgery. Pharm Dev Technol. 2013 Jul-Aug;18(4):957-62.

[3]. Suppression of transforming growth factor-β effects in rabbit subconjunctival fibroblasts by receptor-like kinase 5 inhibitor. Mol Vis. 2010 Sep 16;16:1880-92.

[4]. Inhibition of activin signaling in lung adenocarcinoma increases the therapeutic index of platinum chemotherapy. Sci Transl Med. 2018 Jul 25;10(451). pii: eaat3504.

Objective: Transforming growth factor-β (TGF-β) activity is associated with subconjunctival scar formation after glaucoma filtration surgery (GFS). This study aimed to investigate whether the activin receptor-like kinase (ALK) 5 (also known as TGF-β receptor type I) inhibitor SB-505124 could inhibit TGF-β activity, thereby promoting bleb survival in a rabbit model after GFS. Results: Molecular docking studies showed that SB-505124 interacts with hydrogen bonds at the His-283 and Ser-280 sites of ALK-5. Inhibitory effects of SB-505124 on pSmad2, CTGF, and α-SMA were observed in cultured fibroblasts. Bleb survival time in the SB-505124 group after GFS exceeded 10 days, significantly longer than in the control group. Postoperative intraocular pressure appeared to be correlated with bleb survival. Histologically, compared with the control group, the subconjunctival cell infiltration and scar formation at the surgical site were significantly reduced in the GFS group treated with SB-505124 and mitomycin C (MMC). Immunofluorescence staining also showed that SB-505124 inhibited CTGF and α-SMA. In the ocular tissue block treated with SB-505124 during GFS surgery, cell growth was vigorous, while cell growth was poor in the MMC treatment group. Conclusion: The ALK-5 inhibitor SB-505124 can effectively inhibit the effect of TGF-β in vitro and in vivo. This inhibitor may provide a new treatment method for preventing ocular inflammation and scar formation. [3] Platinum-based chemotherapy resistance is a long-standing problem in the treatment of lung adenocarcinoma. We used genome-wide synthetic lethal RNA interference screening and found that the activin signaling pathway is a key mediator of congenital platinum-based resistance. Transforming growth factor-β (TGFβ) superfamily ligands activin A and growth differentiation factor 11 (GDF11) mediate resistance via their homologous receptors, through TGFβ-activated kinase 1 (TAK1), rather than through SMAD family transcription factors. This resistance can be overcome by inhibiting activin receptor signaling or by blocking activin A and GDF11 with the endogenous protein follistatin. Consistent with the role of activin signaling in acute kidney injury, both of these therapeutic interventions reduced cisplatin-induced acute nephrotoxicity, which is the main dose-limiting side effect of cisplatin. This enhancement of platinum-induced cell death in cancer cells is expected to significantly improve the safety and efficacy of chemotherapy in lung cancer patients. [4]
SB-505124 HCl is also known as TGF-β RI Kinase Inhibitor III and ALK5 Inhibitor III. It is a research compound used to study the TGF-β signaling pathway. It is not an FDA-approved drug and is exclusively for research purposes.

C20H22CLN3O2

371.860583782196

371.14

C, 64.60; H, 5.96; Cl, 9.53; N, 11.30; O, 8.60

356559-13-2

SB-505124;694433-59-5

16079009

Light yellow to green yellow solid powder

5.275

2

4

3

26

466

0

BTUOOXPZOVNPMF-UHFFFAOYSA-N

InChI=1S/C20H21N3O2.ClH/c1-12-6-5-7-14(21-12)18-17(22-19(23-18)20(2,3)4)13-8-9-15-16(10-13)25-11-24-15;/h5-10H,11H2,1-4H3,(H,22,23);1H

2-[4-(1,3-benzodioxol-5-yl)-2-tert-butyl-1H-imidazol-5-yl]-6-methylpyridine;hydrochloride

SB-505124 hydrochloride; SB-505124 (hydrochloride); SB-505124 HCl; CHEMBL1824446; 356559-13-2 (HCl); 2-(5-benzo[1,3]dioxol-5-yl-2-tert-butyl-3h-imidazol-4-yl)-6-methylpyridine hydrochloride; SB505124 hydrochloride;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

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

MEthanol : ~125 mg/mL (~336.15 mM)
DMSO : ~50 mg/mL (~134.46 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (6.72 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 (6.72 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 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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 (Please use freshly prepared in vivo formulations for optimal results.)