SIS3, 500 µg

A cell-permeable selective inhibitor distributed by STEMCELL Technologies, designed to block transforming growth factor β1 (TGF-β1)-dependent SMAD3 phosphorylation and SMAD3-mediated cellular signaling, with an IC₅₀ of 3 µM. The compound is described as a specific inhibitor of Smad3 and does not affect SMAD2, p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), or phosphoinositide 3-kinases. It is classified within the Activin/NODAL/TGF-β pathway.

The product is a crystalline solid identified as 1-(3,4-dihydro-6,7-dimethoxy-2(1H)-isoquinolinyl)-3-(1-methyl-2-phenyl-1H-pyrrolo[2,3-b]pyridin-3-yl)-2-propen-1-one, with molecular formula C₂₈H₂₇N₃O₃ and molecular weight of 453.5 g/mol. Purity is reported as ≥ 98%, and the CAS number is 1009104-85-1. Solubility is approximately 30 mg/mL in EtOH, DMSO, and DMF, and approximately 0.2 mg/mL in a 1:3 solution of EtOH:PBS (pH 7.2).

For storage, the product is stable at -20 °C as supplied and should be protected from prolonged exposure to light; long-term storage is recommended with a desiccant. It is stable as supplied for 12 months from date of receipt. Stock solutions can be prepared in DMSO or absolute ethanol at concentrations ≤ 65 mM. Published applications include facilitating the production of anterior ectoderm from mouse induced pluripotent stem cells (Oshima et al.) and inhibiting myofibroblast differentiation of normal human dermal fibroblasts (Jinnin et al.). The product is for research use only and not intended for human or animal diagnostic or therapeutic uses.