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Identification of Mediators of T-cell Receptor Signaling via the Screening of Chemical Inhibitor Libraries
Published on: January 22, 2019
Screening and identification of a novel class of TGF-β type 1 receptor kinase inhibitor
Q Khai Huynh1, Sarah J Wise, Keith A Koch
1Research and Development, Gilead Sciences, Inc., Foster City, CA 94404, USA. khai.huynh@gilead.com
Abstract:
Transforming growth factor β (TGF-β) type I receptor (activin receptor-like kinase 5, ALK5) has been identified as a promising target for fibrotic diseases. To find a novel inhibitor of ALK5, the authors performed a high-throughput screen of a library of 420,000 compounds using dephosphorylated ALK5. From primary hits of 1521 compounds, 555 compounds were confirmed. In total, 124 compounds were then selected for follow-up based on their unique structures and other properties. Repeated concentration-response testing and final interference assays of the above compounds resulted in the discovery of a structurally novel ALK5 inhibitor (compound 8) (N-(thiophen 2-ylmethyl)-3-(3,4,5 trimethoxyphenyl)imidazo[1,2β]pyridazin 6-amine) with a low IC(50) value of 0.7 µM. Compound 8 also inhibited the TGF-β-induced nuclear translocation of SMAD with an EC(50) value of 0.8 µM. Kinetic analysis revealed that compound 8 inhibited ALK5 via mixed-type inhibition, suggesting that it may bind to ALK5 differently than other published adenosine triphosphate site inhibitors.
Insights
Researchers identified a novel inhibitor, compound 8, targeting activin receptor-like kinase 5 (ALK5) for treating fibrotic diseases. This compound effectively blocks TGF-β signaling pathways, offering a new therapeutic avenue.
Area of Science:
- Pharmacology
- Biochemistry
- Medicinal Chemistry
Background:
- Fibrotic diseases are a significant health concern, and targeting the transforming growth factor β (TGF-β) pathway is a key therapeutic strategy.
- Activin receptor-like kinase 5 (ALK5) is the type I receptor for TGF-β and represents a promising target for anti-fibrotic drug development.
Purpose of the Study:
- To identify novel small-molecule inhibitors of ALK5 through a high-throughput screening campaign.
- To characterize the biochemical and cellular activity of newly discovered ALK5 inhibitors.
Main Methods:
- A high-throughput screen of 420,000 compounds was conducted using dephosphorylated ALK5.
- Hit compounds underwent confirmation, structural analysis, and concentration-response testing.
- Inhibition of TGF-β-induced SMAD nuclear translocation and kinetic analysis of ALK5 inhibition were performed.
Main Results:
- A structurally novel ALK5 inhibitor, compound 8 (N-(thiophen 2-ylmethyl)-3-(3,4,5 trimethoxyphenyl)imidazo[1,2β]pyridazin 6-amine), was discovered with a low IC(50) of 0.7 µM.
- Compound 8 effectively inhibited TGF-β-induced SMAD nuclear translocation with an EC(50) of 0.8 µM.
- Kinetic analysis indicated that compound 8 acts as a mixed-type inhibitor of ALK5.
Conclusions:
- Compound 8 represents a novel class of ALK5 inhibitors with potential therapeutic applications in fibrotic diseases.
- The unique mixed-type inhibition mechanism of compound 8 suggests a distinct binding mode compared to known ATP-competitive inhibitors.
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