CAY10701 is a 7-deazahypoxanthine analog that prevents microtubule formation, blocking the proliferation of HeLa and MCF-7 cells (GI50s = 22 and 38 nM, respectively). It also inhibits the growth of several different colorectal cancer cell lines (GI50 values range from 9 to 17 nM), while being at least 1,500-fold less effective against normal human fibroblast WI38 cells. CAY10701 is effective in vivo, reducing tumor volume in colorectal cell xenografts in mice without significantly altering body weight.