ERBB2 and breast cancer: The compound resulting from the synthesis of ethyl 2-(9-(4-chlorophenyl)-8-oxo-5,7,8,9-tetrahydrotetrazolo[5,1-b]quinazolin-4(6h)-yl)acetate (compound 6) was tested for cytotoxicity in MCF-7/HER2 breast cancer cells [26, 27].