RepSox (HCl), 25 mg

A cell-permeable, selective inhibitor of the TGF-β type 1 receptor (TGFβRI) ALK5, supplied by STEMCELL Technologies as the hydrochloride salt of the molecule. The compound is classified as an Activin/BMP/TGF-β pathway inhibitor.

Reported IC₅₀ values are 4, 18, and 23 nM for ALK5 autophosphorylation, TGF-β cellular assay, and ALK5 binding in HepG2 cells, respectively. Against 9 related kinases, including p38 MAPK and GSK3, activity is much less potent (IC₅₀ > 16 µM). The chemical name is 2-[3-(6-methyl-2-pyridinyl)-1H-pyrazol-4-yl]-1,5-naphthyridine, monohydrochloride, with molecular formula C₁₇H₁₃N₅ · HCl and molecular weight 323.8 g/mol. Purity is reported as ≥ 98%. Alternative names include Alk 5 Inhibitor II, E 616452, and SJN 2511. The CAS number is 2319939-07-4.

The product appears as a crystalline solid. It is stable at -20 °C as supplied, should be protected from prolonged exposure to light, and is stable as supplied for 12 months from the date of receipt. Solubility is reported at ≤ 1.5 mM in absolute ethanol and ≤ 610 μM in PBS (pH 7.2). For use as a cell culture supplement, the stock solution should be diluted into culture medium immediately before use, and final ethanol concentration above 0.1% should be avoided due to potential cell toxicity. Published applications include enhancing reprogramming of mouse embryonic fibroblasts transduced with OCT4, KLF4, and c-MYC; replacing SOX2 in the reprogramming of mouse fibroblasts to induced pluripotent stem cells; direct lineage reprogramming of fibroblasts to mature neurons in combination with CHIR99021, Valproic Acid, Forskolin, SP600125, Gö6983, and Y-27632; and inducing differentiation of human pancreatic progenitor cells into insulin-producing cells, alone or with Forskolin, Dexamethasone, and Nicotinamide. The product is for research use only.