STAT3/NF-kappaB-IN-1 is a potent inhibitor of STAT3 and NF-kappaB, exhibiting IC50 values of 5.86 µM for STAT3 and 4.22 µM for NF-kappaB in 4 T1 cells. It induces apoptosis by upregulating key apoptotic regulators (caspases-3, 9, Bax) and downregulating Bcl-2 expression. STAT3/NF-kappaB-IN-1 shows significant anticancer activity against breast cancer cell lines and can reduce tumor volume in vivo. It is applicable for research in breast cancer.