RepSox, 10 mg

STEMCELL Technologies supplies this small molecule as a cell-permeable, selective inhibitor of the TGF-β type 1 receptor ALK5, also documented in the literature as ALK5 inhibitor II, E-616452, and SJN 2511. The compound is classified as an Activin/Nodal/TGFβ pathway inhibitor. The manufacturer describes it as a crystalline solid with a stated purity of ≥ 98%, a molecular weight of 287.3 g/mol, and a molecular formula of C₁₇H₁₃N₅. The chemical name is 2-[5-(6-methylpyridin-2-yl)-1H-pyrazol-4-yl]-1,5-naphthyridine.

Reported IC₅₀ values from the product sheet are 4 nM for ALK5 autophosphorylation, 18 nM in a TGF-β cellular assay, and 23 nM for ALK5 binding in HepG2 cells, while activity against 9 related kinases, including p38 MAPK and GSK3, is less potent (IC₅₀ > 16 µM). The compound is soluble in DMSO (≤ 30 mM) and absolute ethanol (≤ 3.5 mM), with low solubility in aqueous media; the manufacturer recommends keeping final DMSO concentration below 0.1% to avoid cell toxicity. The product is stable at –20°C as supplied and should be protected from prolonged light exposure, with long-term storage advised in a desiccator.

Published applications include enhancement of reprogramming in mouse embryonic fibroblasts transduced with OCT4, KLF4, and c-MYC; direct lineage reprogramming of fibroblasts into mature neurons when combined with CHIR99021, valproic acid, forskolin, SP600125, Gö6983, and Y-27632; and induction of differentiation of human pancreatic progenitor cells into insulin-producing cells, alone or with forskolin, dexamethasone, and nicotinamide. The product is intended for research use only and is classified as hazardous, with a Safety Data Sheet available from the manufacturer.