This study presents selective oral treatment-mechanism of human breast cancer implanted in mice by a nontoxic antimicrotubule drug, EM015. EM015 selectively treats cancer cells by exploiting their compromised checkpoint mechanisms owing to various mutations, allowing multiple rounds of DNA synthesis without cell division, thus leading to the accumulation of genotoxic DNA amounts and apoptosis. EM015 was synthesized from a naturally occurring alkaloid, noscapine, itself a nontoxic anticough medicine with desirable pharmacokinetic/pharmacodynamic profiles in humans. For details, see the article by Aneja et al. on page 3782 of this issue.