The present study describes: (i) The complete chemical synthesis of monochloro-acetyl-GM3 and dichloro-acetyl-GM3 (referred to hereafter as monochloro-GM3 and dichloro-GM3, respectively), and (ii) evidence that these derivatives show stronger inhibitory effects in comparison with GM3, on the activation of EGFR and of ΔEGFR, a common mutant detected in cancers (9,10). The gene discussed is EGFR; the disease is cancer.