Abstract In continuing search for novel cell differentiation agents, a series of derivatives of indole-3-acetic acid and indole-3-carboxylic acid were prepared and tested against HL-60 cells for their differentiation and antiproliferation activities. Among them, N-ethyl-1- benzylindole-3-carboxamide (14) was the most potent, whereas N-methyl 1-benzylindole-3- acetamide (5) and N-methyl 1-benzylindole-3-carboxamide (13) synergistically ...