Echinomycin (Quinomycin A) is an antitumor antibiotic secondary metabolite isolated from Streptomyces, a quinoxaline antibiotic, a DNA doubly intercalating peptide, and inhibits hypoxia-inducible factor-1 (HIF-1) DNA binding activity. Echinomycin has potential anticancer activity and can be used to study triple-negative breast cancer.