ATRA-BA hybrid is a mutual prodrug form of all-transretinoic acid and butyric acid .1ATRA-BA hybrid is cleaved to release ATRA and BA in isolated mouse plasma. It inhibits the growth of MDA-MB-231 breast and PC3 prostate cancer cells with GI50values of 0.01 and 1.02 μM, respectively. ATRA-BA (20 μM) has 15-fold greater antiproliferative activity in PC3 cells compared to an equimolar concentration of ATRA and BA.