A convenient, sterile-filtered cocktail solution (1000X, in DMSO) containing two small molecules useful for inhibiting SMAD signaling. Can be used to accelerate human pluripotent stem cells (hPSCs) into nociceptors. The two products are the BMP inhibitor LDN193189 (Cat. No. 1995) and ALK5 inhibitor SB-431542 (Cat. No. 1674).