Therapeutic ureas

A compound of formula (IVa):

• wherein:
• X is a group of formula:
• —Xa—Z—(Ya—Z)m—Yb—Z—Xa—;
• m is an integer of from 0 to 20;
• Xa at each separate occurrence is selected from the group consisting of —O—, —S—, —NR—, —C(O)—, —C(O)O—, —C(O)NR—, —C(S)—, —C(S)O—, —C(S)NR— or a covalent bond;
• Z at each separate occurrence is selected from the group consisting of alkylene, substituted alkylene, cycloalkylene, substituted cylcoalkylene, alkenylene, substituted alkenylene, alkynylene, substituted alkynylene, cycloalkenylene, substituted cycloalkenylene, arylene, heteroarylene, heterocyclene, or a covalent bond;
• Ya and Yb at each separate occurrence are selected from the group consisting of —O—, —C(O)—, —OC(O)—, —C(O)O—, —NR—, —S(O)n-, —C(O)NR′—, —NR′ C(O)—, —NR′ C(O)NR′—, —NR′ C(S)NR′—, —C(═NR′)—NR′—, —NR′—C(═NR′)—, —OC(O)—NR′—, —NR′—C(O)—O—, —N═C(Xa)—NR′—, —NR′—C(Xa)═N—, —P(O)(OR′)—O—, —O—P(O)(OR′)—, —S(O)nCR′ R″—, —S(O)n—NR′—, —NR′—S(O)n—, —S—S—, and a covalent bond;
• n is 0, 1 or 2;
• R, R′ and R″ at each separate occurrence are selected from the group consisting of hydrogen, alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, substituted alkenyl, cycloalkenyl, substituted cycloalkenyl, alkynyl, substituted alkynyl, aryl, heteroaryl and heterocyclic;
• L2 is a group of formula (d) or (e):
• R46 is alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, or heterocycle;
• R47 is alkyl, substituted alkyl, aryl, acyl, heterocycle, or —COOR50 where R50 is alkyl;
• or
• R46 and R47 together with the nitrogen atom to which they are attached form heterocycle, which heterocycle can also optionally be substituted with one or more alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, or substituted alkynyl;
• R48 is a covalent bond that attaches L2 to X and
• R49 is alkyl;
• provided at least one of Xa, Ya, Yb or Z is not a covalent bond;
• or a pharmaceutically acceptable salt thereof.