Compositions and methods for inhibiting arginase activity

A compound having a structure of formula (I):

• or a pharmaceutically acceptable salt or prodrug thereof;
• wherein:
• Ra is H or is selected from optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, (cycloalkyl)alkyl, (heterocycloalkyl)alkyl, aryl, heteroaryl, aralkyl, and heteroaralkyl;
• Rb is H or is selected from optionally substituted alkyl, alkenyl, alkynyl, acyl, —C(O)O(alkyl), and —C(O)O(aryl);
• each Rc is independently selected from H or alkyl, or two occurrences of Rc are taken together with the intervening —O—B—O— atoms to form an optionally substituted boron-containing ring;
• X is O or S;
• R1 and R2 are each independently selected from H and optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, (cycloalkyl)alkyl, heterocycloalkyl, (heterocycloalkyl)alkyl, aryl, heteroaryl, aralkyl, and heteroaralkyl;
• R1 and R2 are taken together with the intervening atoms to form an optionally substituted 5- to 7-membered ring;
• and
• R3 is H or optionally substituted alkyl;
• or R1 and R3 are taken together with the intervening atoms to form an optionally substituted 5- to 7-membered ring;
• wherein the compound is not: