Compositions and methods for modulating protease activity

A compound, or pharmaceutically acceptable salt thereof, having the formula:

• wherein
• R1 is independently hydrogen, halogen, —C(O)R1C, —C(O)—OR1C, —C(O)NR1AR1B, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl;
• R1A, R1B, and R1C are each independently
• hydrogen, —CF3, —Cl3, —CI3, —CBr3, —COOH, —CONH2, —CHF2, —CHCl2, —CHI2, —CHBr2, —OCH2F, —OCH2Cl, —OCH2I, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl;
• R2 and R3 are independently an amino acid side chain;
• R4 is —C(O)H, or —B(OH)2;
• when R4 is —B(OH)2, R1 is not