cyclophosphamide + doxorubicin + paclitaxel + vorinostat

This is a combination regimen consisting of four drugs—cyclophosphamide, doxorubicin, paclitaxel, and vorinostat—used primarily in investigational settings for the treatment of breast cancer. Cyclophosphamide is an alkylating agent that crosslinks DNA to prevent cell division. Doxorubicin is an anthracycline antibiotic that intercalates into DNA and inhibits topoisomerase II, leading to DNA damage and apoptosis. Paclitaxel is a taxane that stabilizes microtubules and prevents their depolymerization, thereby inhibiting mitosis. Vorinostat is a histone deacetylase (HDAC) inhibitor that alters chromatin structure and gene expression by increasing acetylation of histones and non-histone proteins; it can sensitize tumor cells to chemotherapy by modulating stress response proteins such as Hsp90[1][3][6]. This combination has been studied in phase I-II clinical trials for locally advanced or high-risk breast cancer (including HER2-positive disease), with the aim of improving pathological complete response rates[1][3].