Provided herein are pharmaceutical compositions (e.g., oral dosage formulations) comprising (S)-4-(4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)oxy)methyl)benzyl)piperazin-1-yl)-3-fluorobenzonitrile, or an enantiomer, mixture of enantiomers, tautomer, isotopolog, or pharmaceutically acceptable salt thereof, and a carrier or diluent. Also provided herein are methods of preparing and methods of using the pharmaceutical compositions.