RepSox, 1 mg

A cell-permeable, selective inhibitor of the TGF-β type 1 receptor ALK5 from STEMCELL Technologies. The compound acts as an Activin/Nodal/TGFβ pathway inhibitor with reported IC₅₀ values of 4 nM for ALK5 autophosphorylation, 18 nM for the TGFβ cellular assay, and 23 nM for ALK5 binding in HepG2 cells. It shows reduced activity against 9 related kinases including p38 MAPK and GSK3, with an IC₅₀ greater than 16 µM in those contexts.

RepSox has molecular formula C₁₇H₁₃N₅ and molecular weight 287.3 g/mol. It is provided as a crystalline solid at a purity of ≥ 98%. Storage at -20°C is recommended, with protection from prolonged light exposure and the use of a desiccant for long-term storage. Solubility is limited to ≤ 30 mM in DMSO and ≤ 3.5 mM in absolute ethanol; the inhibitor has low solubility in aqueous media, and final DMSO concentration in culture should not exceed 0.1% due to potential cell toxicity. Stock solutions should be prepared fresh before use, with aliquoting recommended to avoid repeated freeze-thaw cycles.

Published applications include reprogramming, where RepSox enhances reprogramming of mouse embryonic fibroblasts transduced with OCT4, KLF4, and c-MYC, and supports direct lineage reprogramming of fibroblasts to mature neurons when combined with CHIR99021, Valproic Acid, Forskolin, SP600125, Gö6983, and Y-27632. In differentiation studies, alone or in combination with Forskolin, Dexamethasone, and Nicotinamide, the molecule induces differentiation of human pancreatic progenitor cells into insulin-producing cells. Alternative names include ALK5 inhibitor II, EH616452, and SJN 2511.