Molecular in silico screening against estrogen receptor (ER) protein with caulerpin and the standard drug, mitoxantrone, revealed lower binding of − 11.18 kcal/mol compared to the standard drug (− 8.45 kcal/mol), giving the green light to the possibility of developing the CPE as an anticancer drug lead for breast cancer. The gene discussed is ESR1; the disease is breast carcinoma.