Breast cancer accounts for nearly one-third of all cancers in women, and one of the most aggressive subtypes is triple-negative breast cancer (TNBC). Researchers at Nanjing University and Nantong University developed the β-carboline derivative [I] and showed that it inhibited the growth of various types of TNBC cells in culture as well as growth of TNBC 4T1 xenografts in mice.