Development of novel anti-breast cancer agents.Breast cancer, caused by the development of malignant cells in the breast, is the most common invasive cancer and the second leading cause of cancer death in women after lung cancer. One in eight women worldwide develop breast cancer during their lifetime, and the International Agency for Research on Cancer estimated that breast cancer resulted in 2.1 million new cases and 627,000 deaths in 2018. Anticancer agents are critical for the treatment of breast cancer, but the cost is pretty high: mean per patient per month costs of breast cancer were to be $2,896 (median: $1,940). Moreover, the increasing emergency of drug-resistant breast cancers and the toxic side effects of the drugs have already put heavy burden on the effective control and eradication of breast cancers.The primary objective of this study was to evaluate the potential of bis-isatin scaffolds with alkyl/ether linkers between the two isatin moieties against different human breast cancer cell lines including MCF-7, AU565, MDA-MB-231, MDA-MB-435 and MDA-MB-468 cells.The bis-isatin scaffolds 4, 8 along with the references Doxorubicin and Cisplatin were evaluated for their in vitro activity against MCF-7, AU565, MDA-MB-231, MDA-MB-435, and MDA-MB-468 human breast cancer cell lines by MTT assay.The bis-isatin scaffolds 4 and 8 were sensitive to MCF-7, AU565, MDA-MB-231, MDA-MB-435, and MDA-MB-468 human breast cancer cell lines, and the most active compound 4e was no inferior to that of Cisplatin, highlighting the significance of exploring the bis-isatin scaffolds to fight against breast cancers.The bis-isatin scaffolds are useful templates for the development of novel anticancer agents Other: The enriched SAR may set up the direction for the rational design and development of novel bis-isatin scaffolds with higher efficiency.