Provided herein are compounds of formula (I): which are pro-drugs of epoxy ketone protease inhibitors. The compounds disclosed herein include one or more moieties that (i) confer enhanced solubility, permeability, pharmacokinetics, and/or pharmacodynamics properties to epoxy ketone protease inhibitors, and (ii) can be released in vivo. Also provided herein are pharmaceutical compositions of the compounds of formula (I), and methods of using the compounds of formula (I) to treat diseases and conditions.