SB431542 is a selective and potent inhibitor of the TGF-β/Activin/NODAL pathway that inhibits ALK5 (IC₅₀ = 94 nM), ALK4 (IC₅₀ = 140 nM), and ALK7, but does not inhibit the BMP type I receptors ALK2, ALK3, and ALK6. (Inman et al., Laping et al.) REPROGRAMMING · Replaces SOX2 in the reprogramming of mouse fibroblasts to induced pluripotent stem (iPS) cells (Ichida et al.). · Increases the efficiency of reprogramming human somatic cells to iPS cells, in combination with PD0325901 and Thiazovivin (Lin et al.). · Direct lineage reprogramming of fibroblasts to mature neurons, in combination with CHIR99021, ISX-9, Forskolin, and I-BET151 (Li et al.). DIFFERENTIATION · Promotes differentiation of neural progenitor cells from human PSCs, in combination with either LDN193189 or Noggin (Chambers et al. 2009, Chambers et al. 2012). · Promotes proliferation and sheet formation of mouse embryonic stem (ES)-derived endothelial cells (Watabe et al.). · Enhances differentiation of cardiomyocytes from mouse and human PSCs (Kattman et al.). · Inhibits the self-renewal and causes differentiation of human pluripotent stem cells (PSCs), demonstrating the importance of the TGF-β/Activin/NODAL pathway in their maintenance (James et al., Vallier et al.).